Few things are as disappointing as discovering your cannabis plants or weed stash is infested with mould. These fungal infections can occur in living plants as well as in cannabis harvests stored without proper drying or hygiene. Fortunately, there are ways to prevent such disappointment. This blog identifies several types of mould, as well as explaining how to keep mould on cannabis away from your grows.

How To Spot Mouldy Plants And Buds

Mould on cannabis plants or a stash of dried buds can really ruin your grow. It gets worse, though: mouldy weed can even damage your health. That makes it extra important to regularly check your weed for fungus problems and make sure it’s still safe for consumption. Doing so is a matter of using your eyes and nose. These are the main symptoms indicating mould on cannabis:

Tiny black specks on the flower buds are often early signs of mould;

Yellow, brown, or grey spots that appear ‘fluffy’ indicate advanced mould problems;

Check for unpleasant smell. Plants with fungal issues tend to stink, making them easy to detect by scent. If your weed suddenly starts to smell like sweat or urine, you know it’s time to get rid of it, pronto.

Checking for signs of mould on cannabis plants works best in well-lit environments. Natural daylight is not necessarily optimal; your phone’s flashlight is a nice and bright source of light, but a well-lit room is a good alternative. Make sure you can detect all the colours of the regular spectrum and take the time to thoroughly inspect your buds from all sides. Many people use lenses to literally get a closer look.

If you happen to discover mould on your cannabis, toss it away without hesitation. We hear you wondering: “Really? ALL of it?? Surely, that’s a bit drastic, isn’t it?” Well, we’re sorry, but it’s not. Consuming mouldy weed is a very real health hazard. Don’t think you can wipe off that mould, or just cut away the mouldy bits. Once you see mould appear on the surface of a bud, you can safely assume that the fungus has spread all through the flower and beyond, even if you can’t see it. Don’t risk your health over a few grammes of weed!

Common Types Of Mould On Cannabis

There are three kinds of fungi that cause most of the problems associated with mould on cannabis.

Bud Rot (Botrytis cinerea)

Bud rot is the most common fungal infection found on cannabis. It is more likely to occur in the flowering phase than after the harvest. The process usually proceeds from the inside of the bud towards the exterior.

Aspergillus

Aspergillus, in contrast to botrytis, usually sets in after harvesting the flowers. Airborne spores can cause serious health problems, particularly for those with weakened immune systems. This fungus can cause a condition called aspergillosis, which can spread from the lungs to the kidneys and brain. It is a rare condition, but nonetheless, aspergillus is one of the main reasons to never consume mouldy cannabis.

Powdery Mildew

Mildew is a fast-spreading fungus. Infections can start on any part of the plant, including the leaves as well as branches and stems. Plants wither and die wherever mildew spreads. Plants affected by powdery mildew appear as though covered in talcum powder, featuring white powdery clusters of mould. If you act fast, you have a chance of stopping mildew infections, but if the mould has spread too far, affected plants are usually doomed – and in all likelihood, so are their neighbours.

What Causes Mould On Cannabis

If you want to steer clear of discovering mould on cannabis plants, you need to be careful throughout the entire grow, from germination to growth and from flowering until after the harvest. Mould loves warmth, moisture, and stagnant air. Knowing this, there is much that growers can do to keep their plants and buds fungus-free.

Preventing Mould On Cannabis Indoors

Growing cannabis indoors calls for close monitoring of air humidity and circulation. A hygrometer is a useful tool for measuring humidity. Roughly speaking, the following relative air humidity levels are recommended for avoiding mould on cannabis indoors:

Vegetative stage: 50 – 75% (aim for 60%)

Flowering stage: 45 – 60% (aim for 50%)

Ensure proper air circulation. You can use fans for this, but directing the growth of your plants with techniques such as supercropping can be helpful, too.

A dense foliage canopy increases the likelihood of high air humidity and restricted air circulation. This is why strategic pruning and defoliating plants can help prevent mould on cannabis. Moreover, strong, healthy plants are more resilient to mould. Providing your plants with the right nutrients can help boost their natural immune system.

After the flowering phase, trimming, drying, and curing methods can also affect the chances of discovering mould on cannabis buds. Generally speaking, high humidity, air leaks, and temperature are the main culprits.

Ultimately, however,  hygiene is the key to preventing mould on cannabis indoors. Always try to work as cleanly as possible, and be aware of how easy it is to bring fungi inside. If you have multiple tents or grow rooms, the last thing you want is cross-contamination by (invisible) fungal spores sticking to your clothes and fingers, or just drifting in through the air.

Make sure to clean any grow rooms thoroughly after every grow, and let in plenty of fresh air before starting up a new batch. Proper hygiene is often largely a matter of discipline, so making a habit of working neatly will go a long way towards avoiding mould on cannabis.

Avoiding Mould On Cannabis Outdoors

For outdoor growers, moisture is the main risk factor, usually in the form of rain (drizzle) or mist and fog. Such weather is most likely to set in during the final stages of flowering. By that time, the outdoor cannabis season is drawing to a close in large parts of the world, depending on the year’s weather conditions. At this point, bigger, denser buds become the perfect habitat for all sorts of fungi. This blogs explains how to protect your flowers from mould in the last weeks before the harvest.

The Best Way To Preserve Cannabis

Once you have managed to dry your harvest without contracting mould on your buds, the next step is storing and preserving your weed. Here too, mould can ruin the eventual yield. Luckily, there are various storage techniques that help prevent mould on cannabis nugs.

Plastic Bags

If you are used to store your stash in plastic bags, we advise you to reconsider. Neither regular plastic bags nor zip-lock baggies will protect your weed from heat, cold, or moisture. These baggies are not as secure as you may think. Moisture and high temperatures render your precious buds vulnerable to fungal infection. Moreover, the quality of your stash will fade fast in these bags, as the cannabinoids soon start to deteriorate.

Stash Boxes

You can get purpose-designed stash boxes or similar containers that are airtight and waterproof while blocking UV light. These are a great option for stashing your cannabis flower.

Glass (Mason) Jars

Another alternative comes in the form of glass jars. Whether you prefer classic mason jars or sterilised jam jars put to a new use, glass comes with a number of advantages over plastic containers. You will have to make sure that any jar you use can be sealed with an airtight lid, after thorough cleaning and drying of course. What makes glass containers so particularly useful is their inertia: the glass will not interact with the flower inside (contrary to many types of plastic), setting the perfect conditions for stashing weed inside.

There are added benefits to glass: if you put your jars in a safe place, temperatures will remain stable while keeping air and moisture out and without risking chemical reactions that affect the contents. A good jar will even allow your buds to continue curing as you stash them, further increasing the potency and flavour.

Once your harvest is stashed snugly inside your jars, make sure you find a dry, dark place to store them. Remember that glass jars do not block the light; don’t put them out in direct sunlight. Keep temperatures below 23°C at all times and make sure air humidity remains between 50 and 60%. You can add silica moisture traps to the stashed buds to catch off any remaining moisture if you like.

The Best Genetics Against Mould On Cannabis

Mould is a constant threat hovering over everything that growers and other cannabis lovers do. Fortunately, you now have the right information to protect your harvest and your stash against fungal infections.

Of course, there is one other factor that helps prevent mould on cannabis no matter what the conditions: working with premium genetics! Professional breeders have spent decades developing modern strains with high mould resistance, so use their hard work to your advantage!

Only choose seeds suppliers with their own collection of high-quality strains, and read the product descriptions to find the ones with the best antifungal properties. In case you’re still in doubt, let us assure you that ordering your cannabis seeds at Amsterdam Genetics is a fine first step towards keeping your cannabis free from mould!

Pick Your Mould-Resistant Strains

All things considered, the war against mould will always be an integral part of the grower’s hobby. After all, we are working with nature here, and fungi are an ancient, respectable, and unavoidable part of any ecosystem – including grow tents and gardens. Nonetheless, the tips in this blog will help you protect your own plants as they grow and the harvest they produce, so pick that strain and let’s get growing!

Ordering cannabis seeds, growing them, lovingly caring for them, and then harvesting them at the exact right moment: ultimately, all growers are in it for the flower buds the plant develops in the flowering phase. But just what happens in this flowering phase, and how do you make sure cannabis plants get through it in the best possible shape? This blog explain exactly what flowering entails, and how to go for optimal results.

What Exactly Is The Cannabis Flowering Phase?

Anyone who has ever ordered cannabis seeds online knows that flowering times are an important strain characteristic. Some strains grow faster than others, and sometimes, growers just have to wait while they anxiously search for the first signs of flowering.

The flowering phase brings the ultimate rewards for all cannabis growers. This is the stage where all the love and attention invested in the preceding vegetative phase start to pay off. Slowly but surely, female plants start to reveal their flowers as big fat buds strewn with glittering crystals emerge from between the leaves. This makes the flowering phase the herald of the harvest promised by a cannabis grow.

The ’Flip’ And The Longest Day

Basically, the flowering stage is the same for indoor and outdoor cannabis grows. Garden grows just start flowering differently than grow room or tent projects.

In nature (and in gardens) cannabis plants switch from growth to the flowering stage when it ‘notices’ that the days start to grow shorter. This happens on the longest day of the year, at the summer solstice which occurs at r around 21 June in the Northern Hemisphere. This is a tipping point in nature: autumn approaches, and for perennial plants like cannabis, that means it is time to start producing offspring and start flowering.

Indoors, plants don’t feel how the seasons change, and so growers need to nudge their cannabis into switching to the flowering phase. This is done by reducing the hours of lighting provided by their grow lights. The switch – also called the ‘flip’ – usually involves changing exposure times from 16/8 (sixteen hours of light followed by eight hours of darkness) to 12/12 (twelve hours of light and twelve hours of dark).

The best moment to make the switch depends on the strain involved and the grower’s intentions. The big exception to this procedure is autoflower cannabis strains, which determine when to start their flowering phase autonomously.

What Cannabis Wants In The Flowering Phase

Throughout the flowering phase, cannabis has different needs than in the preceding vegetative phase. Whereas the primary need used to be nitrogen for growth, your plant will need more phosphorus, potassium, calcium and other minerals and trace elements for full flower power. Special flowering boosters and other cannabis nutrition is available, but be careful not to overdo it on the nutes in the flowering phase. Flowering plants are more vulnerable to nutrient burn, and will not recover as well as growing specimens.

Obviously, water is a constant need throughout the grow cycle, but here too, you should pay close attention to what your ladies need to drink at any given day. Keep checking the soil for dehydration and trust your own intuition as well as that of your plants.

Buds, Not Seeds!

To be fair, a grower’s perfect flowering phase is not how cannabis would behave in natural circumstances. Flowering is actually the life stage during which female plants are pollinated to develop her seeds and spawn the strain’s next generation. As growers, though, this is usually exactly what we’re trying to prevent from happening. No matter how fascinating good cannabis seeds are, we tend to do whatever it takes to prevent fertilisation. This is because all the energy plants invest in their seeds comes at the expense of developing the flowers where they would normally emerge. And when push comes to shove, the flowers are precisely where we find all those lovely trichomes loaded with THC, CBD, terpenes, and all other natural cannabis treasures…

Cannabis Birth Control In The Flowering Phase

This makes birth control one of the prime goals throughout the flowering phase, to ensure a harvest full of sticky buds instead of seeds. This explains why growers go to great lengths to prevent pollen from reaching their female plants. For most grows, this starts with ordering feminized cannabis seeds. These special seeds grow up to be female plants in 98% of all cases. By contrast, buying regular non-feminized seeds gets you about a fifty-fifty chance of getting male specimens.

Still, even fully feminized seeds can’t guarantee a 100% girls-only grow tent. Sometimes, males just pop up among a cannabis grow, which you’re unlikely to notice until the flowering phase begins.  That means keeping your eyes peeled, because the moment you spot male reproductive organs, you’ll want to carefully remove the whole plant to minimize the chance of pollination.

But even if you’re sure you have only female cannabis plants, things can still go south in the flowering phase. Stress can cause marijuana plants to turn into hermaphrodites with both male and female genitalia. These hermas can then pollinate females or each other, resulting in a seed-riddled harvest despite your best intentions. This separate blog explains how to identify male and hermaphrodite plants, and what to do if you spot them in the flowering phase.

Duration Of The Cannabis Flowering Phase

How long the flowering phase lasts depends on the cannabis strain involved. Sativa strains have a particular reputation for prolonged flowering times, which can reach up to three months from the initial signs of flowering to the moment they’re ready to harvest. Indica genetics tend to flower faster, sometimes only seven or eight weeks. These days, however, most available strains are hybrids containing both indica and sativa traits. Always determine the flowering times of the strains you like before you order seeds.

The shortest flowering times are usually reserved for autoflower strains. These contain ruderalis genetics originating from rugged places with bad weather. These harsh conditions forced ruderalis to evolve into a plant that speeds through its life cycle and finish flowering before the early end of its season. Sativa cannabis instead tends to have extended flowering phases due to its tropical origins with plenty of time for bountiful growth and flowering. Indica strains usually range somewhere in between, which only adds to the variation found in today’s available hybrid strains.

The First Signs Of Flowering

As you can see, knowing when your plants start flowering is absolutely crucial. This is the moment to spot and weed out any males and hermaphrodites, but it’s also an indication of how long it will take before you get to harvest.

‘Hairs’ Or Pistils

The early signs of the flowering phase appear on female cannabis plants in the form of tiny white ‘hairs’ forming in the nodes. The stage at which these white pistil hairs start to show is sometimes called preflowering. The hairs grow out to be the pistils of the eventual flower. Pistils are female reproductive organs intended to receive pollen spread by male plants. Cannabis reproduces by airborne pollination, unaided by bees or hoverflies like other species. This is how a single male can ruin an entire grow by pollinating the entire garden or grow room population.

Sugar Leaves

After a week or two of flowering, small sugar leaves start to emerge around the pistils. This starts in the form of clusters of small, on-fingered leaves called sugar leaves. These sugar leaves are part of the buds that make up the harvest yield. After harvesting buds are trimmed, the leftover sugar leaves can be used for all sorts of purposes, as this blog explains.

Cannabis Colas, Apex Of The Flowering Phase

The fledgling buds that form at the nodes around the pistil hairs and sugar leaves are officially called colas, but we usually label them buds, flower buds, nugs, or just flowers. These cannabis colas are what the flowering phase is all about. This is due to the trichomes that dot the flower buds: small glands filled with resin full of cannabinoids and terpenes. These re the compounds that cause the high. Their concentrations differ from strain to strain and even between individual plants, which explains why cannabis can have so many different effects.

In fact, however, trichomes were never ‘intended’ to make cannabis lovers happy. They are actually meant to protect fragile buds against hazards such as UV light and harmful insects. Ironically, though, they tend to attract a special breed of apex herbivores: in the flowering phase, cannabis growers aim to make flower buds produce a thick layer of gleaming trichome ‘crystals’. Trichomes are a grower’s best clue as to when a bud is perfect for harvesting. You can learn how to tell when a cola is ready to harvest in this separate blog. At that moment, the flowering phase has come to an end, and the harvest can begin in earnest.

Risks

The flowering phase brings other dangers besides the risk of hermaphrodite and males cannabis plants: more so than the growth phase that came before. Flowering makes plants more vulnerable to stress and problems linked to soil condition, nutrients, water, and disease. On top of that, the fragrant flower buds tend to attract a specific type of predator, which includes the dreaded Nosy Neighbour.

Cannabis plants also have different nutrient requirements in the flowering phase. Whereas the steeple diet consisted mainly of nitrogen for growth in the vegetative stage, other compounds become more important now. Keep this in mind if you decide to feed your plants, but always be cautious when adding nutrients in the flowering phase. Mistakes can have dire consequences that your crop will not recover from with the same flexibility it had in the growth phase.

Outdoor cannabis growers have another formidable enemy in the flowering phase: the weather. Many areas with moderate climates mark the close of the outdoor grow season with downpours, fog, and storms capable of decimating a grow right before the finish line. Read this blog to learn smart ways of protecting outdoor weed from bad weather.

Finishing Flowering Indoors

In the late stages of the flowering phase, the weather can cast an ominous shadow over the final results of any outdoor grow. Growers who don’t want to take their chances and those faced with delays in flowering can opt to finish flowering indoors. This lets them drag their plants into safe and comfortable warmth of a grow tent or room to make the most out of their harvest yields. In some cases, a greenhouse can come in very handy as well.

Finishing the flowering phase indoors can really save a cannabis harvest from disaster, but it does involve certain risks as well. One of these is stress. Outdoor plants in pots are not hard to bring inside to bask in the bright glow of grow lights, but the sudden change of scenery can be a major source of stress, too.

Another problem of taking plants indoors is the risk of inadvertently bringing in more than you intended to. Pests, mould, and diseases already present on plants can go into overdrive once they’re snug in the comfort of your home, which will make your problems worse than they were out in the rain. Always make sure to spray your plants well first, preferably using some sort of organic plant detergent, but even then, you should keep a close eye on how the grow behaves indoors.

A final problem with late indoor flowering is the size of your plants. If you decided to plant that beautiful sativa strain in your garden and it grew to be two or three metres tall, you’re going to have a hard time squeezing it into that tent at this stage. You could decide to consider projected plant size when deciding which cannabis seeds to pick before starting your next grow.

From The Flowering Phase To A Bountiful Cannabis Harvest

The moment a grower decides that the flowering phase is complete, it is time for the cannabis harvest. This blog explains how to bring the harvest in safe and sound. If you’ve added lots of nutrients, your best option is to flush your plants before harvesting. Flushing means giving a pant nothing but pure water in the final week of the flowering phase to wash out any excess nutrients. This will leave you with better-tasting buds and cannabis with minimal pollutants at the end of the flowering phase.

Harvesting, Trimming, Drying & Curing

Now that you know what the flowering phase entails, you’ll probably want to know how your cannabis quest continues. In fact, there’s a lot of work waiting for any grower after flowering is complete. You’ll need to bring in the harvest for drying and trimming (though not necessarily in that order). Once the harvest is dry, you can cure the buds to bring out all the fragrance and flavour they contain. Only then will you finally be able to savour that hard-earned cola reward…

Let’s get those seeds to flower!

Enjoying The Flowering Phase

One more piece of advice: don’t forget to enjoy the flowering phase itself before it’s over. It is fascinating to watch the slow fruition of the flower buds as they form trichomes and steadily start to spread their scent. Do yourself a favour and observe your ladies in full bloom whenever you get the chance. Let your imagination run wild, because a flowering cannabis plant is enough to start most growers’ mouths watering in anticipation!

When growing weed, most growers are fully focussed on achieving optimal harvest results. That is why they tend to concentrate their efforts on the flower buds that develop in the flowering phase, sice these contain the cannabinoids and terpenes that determine the effect and flavour of the weed. Still, growers should also have some basic knowledge on the stems and branches of cannabis plants. This blog zooms in on their function and anatomy, as well as exploring their use for human consumption.

Location Of Cannabis Stems And Branches

At the risk of stating the obvious, a discussion of cannabis stems and branches should start out by determining where they are. The appearance of cannabis plants can vary considerably depending on strain genetics, but broadly speaking, all variants have similar branches and stems.

Stem

The stem or stalk of a cannabis plant is the upright part of its ‘frame’. The stem begins right above the roots and ends at the top branches. This is the section that races upwards throughout the growth phase of the cannabis life cycle. The plant’s branches start their growth from the stem, at the points where the nodes develop.

Main & Side Branches

In cannabis plants, branches are in fact extensions of the stem. Whereas the stems determine the height of cannabis plants, branches make up their width. Wherever nodes line the stems, main branches usually branch off to either side and then grow upwards, potentially splitting into further side branches.

From the moment when cannabis seeds germinate, these pairs of branches start to develop into the eventual canopy shape. Main branches divide into side branches, and so on, until the final plant structure takes shape. The characteristic marijuana fan leaves then grow from these branches. During the flowering phase, female plants develop cola buds with trichomes full of active compounds at the same nodes where branches emerge.

Nodes & Internodes

Cannabis stems can be divided into internodes, or internodal spaces. These are the sections separating the plant’s nodes. In other words, every cannabis plant has an internode between every pair of branches sprouting from the nodes. It’s important to watch these nodes closely at the onset of the flowering phase, as this is where the male reproductive organs emerge in case of male or hermaphrodite cannabis plants hidden among your feminized specimens.

Functions Of Cannabis Branches And Stems

The primary function of cannabis stems and branches is to provide support and the right shape. As plants get heavier while they grow, its supporting framework must remain strong enough for the leaves and flowers that emerge. Quite a few grow techniques revolve around manipulating this structure for improved harvest yields. This is usually done by giving a plant a more open structure for improved light distribution, or by changing its overall shape to make it fit a grow room or tent.

Firmness and flexibility are integral parts of this structure. Cannabis plants have to stay strong and sturdy yet flexible enough to prevent stems and branches from snapping in a storm, or because of passing deer and neighbours. Plants balance these two qualities through a combination of the strong fibre making up the stems and branches (firmness), the process of osmosis that keeps cells firm, and the hollow space within stems and branches for flexibility under duress.

Stems and branches also govern transport of water and nutrients throughout the plant. Water is absorbed by the roots and then driven upwards to the leaves by the xylem, a one-way system of microscopic tubes located within the stems and branches. Nutrients can be transported both up and down by the phloem, a second vascular system situated closer to the outer wall of the bark.

What Can You Use Cannabis Stems And Branches For?

Since the dawn of mankind, cannabis flowers have been used both for recreational and medicinal purposes. And yet, cannabis, or actually hemp, has also been employed and grown throughout history for the fibre in its stems and branches. This so-called fibre hemp grows fast and easy, enabling rapid production of extremely strong fibres. These fibres have been and are being used for all sorts of products, ranging from textile and rope to sails and modern construction materials. These days, for example, hemp fibre is applied in construction as prefab blocks used for building strong, sustainable, high-insulation walls. In fact, hemp cultivation used to be so important back in the day that many countries enforced mandatory cannabis plant production quota on farmers – a far cry from the situation we find ourselves in today…

Cannabis stems and branches have limited use for human consumption. These parts of the plant hardly contain any cannabinoids, so making hash or edibles from stems and branches is unlikely to produce much of an effect. Of course, you could still use them for their flavour as a herbal twist to home-brew tea, but don’t count on getting high from it.

Once the harvest is drying (usually hanging upside-down by its branches – that’s yet another function!) you could simply toss all the leftover stems and branches in the bin. That would be a real waste, though, since stems and branches of cannabis plants are just as great for making compost as the leaves. Making your own cannabis compost gets you balanced and natural soil life for next year’s grow: a clever, economical, and sustainable use for those stems and branches!

Training & Techniques

Cannabis growers use various techniques that revolve around manipulating branches and stems. Take the Screen Of Green method for example, which involves spreading the branches using a wire framework to improve lighting of the lower leaves. Low Stress Training is a technique that manipulates branches with a gentle touch. Supercropping is about bruising and twisting branches on purpose without tearing the outer bark. If you get it right, the plant will continue growing upwards from there, allowing better adjustment to grow room dimensions as well as improved light distribution for the whole plant.

In indoor cannabis growing, limiting the height of stems and branches Is often a prime concern, especially for sativa genetics that tend to shoot up to the roof. Growing cannabis outdoors poses its own unique set of challenges. Perhaps plants should not grow over the hedge for privacy reasons? If so, the techniques listed above can also work out in the open. In the open air, storms are a substantial risk, so you may want to support your plants’ stems with some bamboo just in case. Just be careful not to fix them too tightly or you’ll risk cutting of sap flows and damaging your plant.

Right after germination and throughout the early vegetative phase, cannabis stems and branches are at risk of a phenomenon known as stretching. Stretch occurs when a seedling races up to the light too fast, resulting in flimsy, thin, elongated stem development. Thoughts on how to prevent and counter stretching are discussed in this separate Grow Blog.

Let’s Get Growing

Now that you know the basics of cannabis stems and branches, you have a more solid backbone to work with – as will your plants. That means it’s high time to start that new grow – you’ll find the finest genetics in our online catalogue, from roots to stems and from branches to the buds we’re all aiming for!

Pick Your Prime Genetics

This blog zooms in on cannabis leaves and their uses for plants and growers. As a cannabis community, we tend to focus on the flower buds of our beloved plants, but this blog explains why leaves are crucial for any attempt to grow, understand, and truly enjoy cannabis.

History Of Cannabis Leaves

Cannabis leaves are the most iconic symbol of modern stoner culture. They may well be the most famous and identifiable type of foliage in the world (sorry Canadian flag!). That’s actually weird, since cannabis growers are usually out to harvest the plant’s flower buds, not the leaves. Still, the tell-tale shape of a weed leaf has been making its mark on society for ages. It has been spotted in ancient East Asian cave drawings and Egyptian hieroglyphics, predating the invention of agriculture and crop cultivation in some cases. Moreover, riding today’s wave of legalization and international recognition, cannabis leaves are more ubiquitous in subcultures and mainstream branding than ever before.

So even if most of the medicinal and recreational benefits of cannabis are located in the cola buds of female specimens, it pays off to understand the functions and biology of its leaves. As this blog explains, leaves are crucial for the growth and survival of cannabis plants. In addition, they have been used by shamans, priests, and healers throughout the centuries. However, for growers, they serve another crucial function, signalling many health issues and other problems that plants face throughout their life cycle.

Vital Functions Of Cannabis Leaves

Most plants have leaves, hinting both at their ancient evolutionary origins and their extreme importance in plant survival and physiology. At any rate, leaves make up most of the mass and surface of a cannabis plant, making basic leaf knowledge essential reading for all growers and connoisseurs.

Photosynthesis

The main biological function of cannabis leaves is photosynthesis. As this blog explains, photosynthesis is a series of chemical reactions allowing leaves to turn (sun)light into energy, which they can store and use to fuel growth and flowering. Leaves are the solar cells of plants, which explains why total leaf surface is such a vital aspect of a plant’s physiology and chances of survival

Nutrient & Water Storage

Cannabis leaves can also be used as a storage facility for water and important nutrients, especially nitrogen. If times get tough, these reserves can be drawn from the leaves and used as an emergency supply. This largely explains why so many cannabis (nutrient) problems become apparent in the looks of the leaves, which can turn yellow or brown due to nutrient shortages.

Breathing & Feeding

Not everyone knows that leaves can also absorb and release various compounds, similar to the main function of a plant’s roots. In fact, this is why plants are so essential to keeping our atmosphere in good shape. When they catch the light, cannabis plants absorb CO2 through the pores or stomata located underneath their leaves. CO2 is used for photosynthesis, to produce the sugars (carbohydrates) that fuel the plant’s metabolism.

In the dark, they release O2 back into the air. This explains why plant life acts as a carbon sink trapping harmful excess CO2 from the atmosphere, and how they can help keep the air in a room healthy. It’s also nice to know that growing weed is a small contribution to keeping climate change in check; or at least to partially offset energy consumption of grow lights for indoor growers…

The pores on the surface of cannabis leaves can also absorb water. This is why growers can water and feed their plants using the leaves in addition to the roots. Spraying water with some nutrients in it can contribute to healthy plant growth, provided it is done in moderation.

Transpiration

Leaves have transport channels through which water drawn up by the roots reaches the leaf cells. This makes leaves firm through a process called osmosis. If the leaves on a cannabis plant start to go limp, the likely cause is water shortage, causing osmotic pressure to drop and cells to go limp, resulting in drooping leaves.

Shade

People often overlook the importance of shading provided by the leaves of a plant. Sure enough, they catch light for energy production, but they also keep the lower parts of the plant cool by the shade these ‘solar panels’ cast. This is a bit of a double-edged sword for cannabis growers, however, as too much foliage can restrict the amount of available light for the plant as a whole. Some grow techniques such as SCROG attempt to maximize leaf spread to make the most out of available (sun)light. We have a special blog on pruning cannabis plants that tells you all about what to cut, and what to leave on the stems.

Types Of Cannabis Leaves

We can distinguish between three types of leaves on a cannabis plant: cotyledons, fan leaves, and sugar leaves.

Cotyledons

The first things to emerge from a cannabis seed after germination are a tap root and a pair of cotyledon leaves. These baby leaves don’t have the typical weed leaf shape. They are the first miniature solar panels the seedling employs to power development of the true fan leaves that come after.

Fan Leaves

Fan leaves are the world famous symbol of weed. You could call them the ‘true’ cannabis leaves. Their characteristic serrated edges and slender leaflet fingers are quite easy to spot, which explains their branding value. But not all fan leaves are created equal. Different types of cannabis have different leaf characteristics.

Cannabis indica strains and indica-heavy hybrids tend to have shorter, broader leaves with bright or lime green colours. The differences between indica and sativa weed are disputed, but there is a tendency to discern ‘broadleaf variants’ that are generally indica-leaning in their genetics. Indica broadleaf fan leaves tend to have fewer fingers or leaflets; usually between five and seven in mature leaves.

Cannabis sativa strains and their hybrids usually display longer, slender leaves that have darker hues. They also have more leaflets per fan leaf than indica-heavy strains, often somewhere between seven and eleven or even thirteen in total.

Cannabis ruderalis – the type mainly used in autoflower crossbreeds – tend to have the fewest leaflets, often growing in three-fingered constellation. It is rare, however, to see a 100% ruderalis plant, so these properties usually don’t show in commercial autoflower strains.

Some breeders aim for a specific type of uncommon and mutated leaf shape called ‘duckfoot’. Duckfoot leaves are also three-fingered, but they don’t need to have ruderalis descent. This is a bit of an acquired taste, sought after by specialist growers, but duckfoot cannabis leaves nonetheless deserve mentioning in a blog like this.

Sugar Leaves

The third main type of cannabis foliage is sugar leaves. These are smaller leaves with fan-like shapes found in and around the buds as they mature. Sugar leaves are often loaded with trichomes containing valuable cannabinoids. When harvesting weed, sugar leaf trim should not be discarded, as they can be used for making hash, edibles, and more as this blog explains.

How To Diagnose Cannabis Health Through Leaves

Leaves are an important part of the anatomy and physiology of cannabis plants. For growers, they have another vital function: leaves can be key indicators of a cannabis plant’s health. The various signals and symptoms cannabis leaves can convey are too much to address in this blog, so these will be dealt with separately. However, to give you an indication, cannabis leaves can be used to detect a range of problems including:

• Nutrient Burn/ Shortage;
• Water Issues;
• Mould;
• Pests;
• Disease;
• Stress.

Let’s get one common misunderstanding out the way right here and now. Yellow leaves are often a sign that something is wrong with a cannabis plant. However, there is one case in which yellow foliage is perfectly normal: late flowering. Once the flowering stage is almost complete, the plant starts to shed its fan leaves, which starts by the leaves turning yellow. This is perfectly normal plant behaviour intended to drain leaves of all remaining nutrients for maximum flower bud growth.

Pruning And Leaf Based Training

As mentioned, pruning cannabis leaves can be difficult to master. Our pruning blog gives a few good guidelines, but most growers stick to their personal preferences and best practices when it comes to removing leaves.

Several specialized grow techniques aimed at maximizing harvest yields rely upon removing leaves or altering a plant’s shape to give leaves more room. These techniques, including SCRoG (Screen Of Green), Low Stress Training, and SoG (Sea Of Green) are covered in separate Grow Blogs.

What To Do With Cannabis Leaves?

Once the leaves of a cannabis plant have served their purpose fuelling growth and bud formation, growers harvest the flowers and generally discard the remaining foliage. This is actually a crying shame. Both the fan leaves and sugar leaves have their uses for holistic cannabis enthusiasts; moreover, reusing all that plant material gives your grow that extra touch of sustainability.

Sugar leaves tend to be sticky with glistening trichomes once cannabis finishes flowering. The leaves themselves are too acrid-tasting to smoke, but they are great material for making hash, extracts, cannabutter, or other edibles. Never throw these away while trimming buds – they’re a real treat reserved only for those who grow their own!

Fan leaves don’t contain enough cannabinoids for making hash or other delights. Still, they are full of valuable compounds that any grower can reuse for free. Cannabis leaves make the best compost for next year’s grow. All it needs is a place to decay, without any further effort on the grower’s behalf!

Some growers also make ointments and tinctures out of cannabis leaves after harvest for the non-cannabinoid compounds they contain. Recipes abound online if you’re interested.

Turning A New Leaf

Now that you have some basic knowledge on cannabis foliage, you’re likely to appreciate your plant’s hard work even more than you already did. Knowing what to do (or not to do) with leaves will only improve future grow results. Feel free to browse our Grow Blogs for more cannabis info and tips, or proceed straight to our strains collection and order fresh seeds to turn a new leaf for your next grow…

Do you use cannabis for stress relief? Good on you! But did you know that your cannabis plants can suffer from stress, too? If they do, you need to intervene and help your grow through stressful times. You can recognise cannabis stress from various symptoms and signals, including dry and yellow leaves or poor root development. This blog explains how to detect stress in cannabis plants as well as how to prevent or treat it.

How To Detect Cannabis Stress

Stress equals tension and the feeling of being under pressure. People as well as other animals are known to be susceptible to stress, but plants such as cannabis can suffer from it as well. Stress occurs when grow conditions are not ideal. Long-term stress can slow the growth of cannabis plants, or even damage them permanently.

Signs Of Stress In Cannabis Plants

• Dry, wilted leaves;
• Yellow or brown leaf edges and tips;
• Bud mould or rot;
• Curling leaves;
• Brown, slimy, stinking roots;
• Hermaphrodite plants;
• Tall, thin stems (‘stretching’).

Many different factors can cause stress in cannabis plants. As soon as you spot the first signs, you need to find out what caused them. If you manage to take away the cause, your plants are likely to recover quickly, putting you back on track towards good harvest results.

Causes Of Cannabis Stress And How To Tackle Them

Do you see indications of stress on your plants? Below, you’ll find a list of potential causes along with tried techniques to solve the issues.

Air Humidity And Temperature

Cannabis is a hardy plant that can take quite a beating. The species can thrive in a range of different climates, with an innate ability to tolerate less-than-optimal conditions. Still, growers aiming for maximum growth and flowering results need to keep temperatures and air humidity well within tolerable limits. Cannabis loves a bit of warmth, but if temperatures rise above 26°, it needs to cool down to prevent heat stress from occurring.

Indoor cannabis growers can opt for installing an air conditioning unit, although this is a costly investment. Adequate ventilation supplying cool outside air, paired wit exhaust fans to carry of warm air, can also go a long way towards keeping temperatures within acceptable limits. Do make sure to install high-capacity filters to stop the scent from spreading. Outdoor growers have their own set of interventions to prevent heat stress, such as building a shelter for their cannabis crops.

High air humidity can also cause serious stress in cannabis plants. This is more of an indoor grower’s issue. Air dehumidifiers can be a good solution for keeping indoor climate in check. High temperatures and high humidity can stunt plant growth and produce buds with an undesirably open structure.

Soil Quality

The soil in which cannabis grows can also be a cause of plant stress. Growers use all sorts of grow mediums for their projects, each with their own pros and cons. Clay soils, for instance, have insufficient drainage capacity that make it easy to add too much water. Sandy soils, by contrast, drain water too easily, carrying off essential nutrients with it. It can be worthwhile to reconsider your preferred soil type. Most soil problems can be solved by mixing different types of soil together.

Remember that good soil is always more than ‘just dirt’. Facilitating healthy soil life can help any strain feel more at ease.

Bugs And Diseases

Another cause of stress comes from bugs and diseases that target cannabis plants. If plants notice they are under attack from pests or get sick, they will initiate a stress response at the expense of further growth and flowering. Be sure to arm yourself with knowledge on how to keep bug like slugs, aphids, and more at bay. Our tip for outdoor growers: use companion planting and give your crops some neighbours that help protect them against threats and stress.

Light And Dark

Cannabis plants are very sensitive to changes in the amount of light they receive. Fluctuations in the amount and intensity of light have an impact on growth. Plants that grow outdoors get all the light they need as the seasons take their course. Inside, however, growers are responsible for providing enough light and darkness.

Lighting issues can cause excessive stretching as well as turn plants into hermaphrodites with both male and female traits, and ruin your harvest in the process. Pay attention to good circadian rhythms and use the appropriate light spectrum. Make sure all plants and leaves receive just enough light to prevent stress from affecting their growth.

Cannabis Stress Due To Bad Weather

Indoor growers have extensive control over grow conditions, but outside, we have to rely on the weather. Weather can be an unpredictable factor to work with. These days, dry spells in spring and heatwaves or downpours in summer are becoming increasingly common. Obviously, such weather affects cannabis plants, causing stress if its impact becomes too great.

Cold weather during the vegetative phase can arrest the growth of your plants. If these conditions persist, plants could even die. If you find your plants suffer from cold stress, the best thing to do is taking them inside for a bit. Obviously, this works better if you’re growing in pots rather than in open soil.

Excessive moisture can also stress out cannabis plants. If plants are left out in damp weather for too long, they become vulnerable to mould and rot. Of course, storms can also cause damage that your plants may not be able to overcome. Sadly, there’s not much you can do beyond prevention: try to take wind direction into account when picking a spot, and provide as much cover as you can.

Water And Nutrients

Watering plants seems a walk in the park – until you try to get it right. Giving too much or too little water can be a cause of cannabis stress, too. This becomes apparent in abnormal growth patterns, discoloured leaves, and stunted root development. Also keep in mind that your plant will have different needs in different phases of its life cycle.

Adding too much or too little water and nutrients can disrupt the balance of key minerals and other nutrients such as nitrogen, magnesium, phosphorus, and potassium. Nutrient stress usually becomes apparent in the leaves: they can turn yellow at the tips or appear burned (‘nutrient burn’) and fall off. Too much water can deprive roots of oxygen and cause them to rot. Of course, water shortages are harmful too. If you want to learn more about watering cannabis correctly, check out this blog.

Stress From Cannabis Training

There is one last cause of cannabis stress we need to mention: training techniques. Our Grow Blogs contain various methods aiming to improve the efficiency of a grow and increase harvest results. Awesome as this may sound, these interventions usually come with specific cannabis stress hazards.

‘High stress training’ techniques like topping, fimming, or mainlining are particularly risky undertakings. Always act with caution, and if possible, apply techniques to a few plants only. That way, you’ll still have part of your cannabis grow left if stress problems occur.

Stress Free Cannabis Growing

Stress can have disastrous consequences for humans, from sleepless nights to full-blown panic attacks and heart conditions, but is can harm cannabis, too. Luckily, any grower can try to prevent stress, or help their beautiful cannabis plants cope with any stress they do experience. Generally speaking, overcoming stress tends to be easier for plants than for people. As long as basic conditions are met (water, light, nutrients, fresh air), cannabis crops will flourish with minimal stress.

Order Your Seeds With Zero Stress

That makes for a beautiful cycle. If you manage to keep your plants free from stress, your cannabis may help you lose your own stress in return!

Warmth, sunlight, overexposure and heat stress can cause serious harm to any cannabis grow. Of course, all cannabis plants need (sun) light for the photosynthesis that fuels their growth and flowering. But you can have too much of a good thing. This blog explains why heat can cause problems both indoors and outside, and why protecting cannabis is crucial for good harvests.

Why Protect Cannabis Against Heat?

In nature, all processes run most smoothly within certain parameters, no matter whether it’s plants, animals, or even single-cell organisms. Every plant species has an ideal combination of environmental factors for growth and flowering. No matter whether it’s air humidity, soil moisture conditions, acidity, amount of light, or temperature: if even one of parameters falls below or exceeds its critical limits, the wellbeing and, ultimately, the existence of the organism is threatened.

Sadly, temperature (heat, that is) becomes more of a risk factor year after year. Anyone who has been growing weed for a couple of years will have noticed how our summer weather is changing. Heat waves are getting more common. That’s fine when you’re spending the day on the beach, but al that heat is far from cool if you’re trying to grow weed outdoors. Heat is problematic indoors as well, by the way, since grow lights emit heat that can be harmful for plants. Just like us, plants tend to do better if they have minimal stress in their lives.

Heat Stress Symptoms

During a cannabis grow, heat can be a total disaster long before harvest time arrives. The damage caused by excessive heat is called heat stress. The plant actually react with a stress response. The usual signs of cannabis heat stress are the following:

• Dried-out, exhausted-looking plants;
• Curled-up tips of fan leaves;
• Brown spots along the edges of leaves;
• Odd cola shapes.

All of these symptoms can manifest while cannabis plants flower, but they will often appear far before that time. That is why the symptoms visible on the leaves are often the main warning signs.

During the vegetative phase, cannabis plants need lots of light. Light is energy: useful if you want to draw grow power from it by photosynthesis, but considerably less awesome if you get al that energy straight in your face.

In the flowering phase, signs of heat stress can show on the leaves too, but the shape of flower buds can also be an indication. If you see a thriving bud with a kind of extra mini bud growing op top of that, beware: these ‘foxtail’ shapes can be a sign of excessive heat.

Protecting A Cannabis Grow Against Heat

When it comes to heat stress, prevention is better than cure. Once heat has damaged plants, they tend to recover poorly, which seriously threatens the eventual harvest yield. That just makes protection and prevention more important. The best way for a grower to protect their cannabis from heat, however, depends entirely on the causes. Logically, these causes will usually differ between indoor grows and garden or balcony projects.

Growing Outdoors: Sunscreen For Your Crops?

Even though any cannabis plant loves a fair bit of sunbathing, they are much like us in terms of the health concerns of overexposure. Another similarity with humans: as the climate is changing and extreme weather events become more common, our cannabis needs protecting against heat (waves) and intense sunlight. Thankfully, there are several ways to do just that, and they’re not hard to pull off if you know what you’re doing.

Finding The Best Spot

When growing outside, it is crucial to find the best spot for your plants before the grow kicks off. Think carefully about the influence of both rain and sunlight on different parts of the garden (or balcony). Wind is definitely a factor to consider, too: is there enough cover to survive a summer storm? You can read more about picking the perfect outdoor grow spot in this blog.

Mobile Weed    

One clever way of protecting cannabis against heat is keeping it mobile, i.e., growing in pots rather than in open soil. This way, a plant can enjoy all the sunshine, rain, and fresh air it needs whenever the weather is nice. If it’s going to be a hot day, you can simply move them to a shaded spot until the danger subsides.

Be careful with pots, however, as they make the roots of the plant more vulnerable to heat stress. Black planters in particular tend to heat up fast out in direct sunlight. This will accelerate moisture evaporation while making rot more likely. You can tackle this issue by adding a protective buffer around the pot. Placing the pot inside another, larger pot is one solution, but covering the top soil layer with straw is another easy way of protecting potted cannabis from heat hazards.

Shelter And Shade

Even growers with only modest DIY skills will find it fairly easy to build their plants a home-made shelter. A bit of clever carpentry and some hinges will do the trick, as will a simple frame and some tarpaulin sheeting to pull over it. This latter option is also a means of protecting cannabis from heat in open soil.

Be mindful of grow spots on balconies or near walls, as these tend to create heat zones by reflecting sunlight. Try to avoid these hotspots, but if you can’t, at least you’ll know you will need some sort of cover before you start. It will also help protect your grow from the wind and rain, which comes in extra handy during the final vulnerable phase right before the harvest.

Having a greenhouse in the garden makes everything easier, as you’ll already have a frame you’re your tarp cover if necessary. But growing weed in a greenhouse has other benefits too, as this blog explains.

Water And Nutrients

Please avoid the mistake of protecting cannabis from the heat of the sun by using water. Watering plants out in full sunlight turns droplets into prisms that only intensify the rays, which increases burn and heat stress risks rather than reducing them. Of course, plants out in the hot sun will lose more moisture through evaporation, so be sure to give enough water to prevent dehydration. On hot days, the best time to water your plants is either early in the morning or after sunset. This blog explains all about smart watering.

Adding certain kinds of nutrition can also help make cannabis plants more resilient to heat. Seaweed such as kelp is an example, as are silicon-based supplements and special-purpose root boosters. However, here too, adding too much of a good thing can be harmful. You can find out more about nutrition in this blog.

Indoor Growing: Lighting Up

Let’s start by stating the obvious: when growing cannabis indoors, protecting your pants against  the heat of the sun should not be necessary. Indoors, lighting is the main risk factor, being the sole light source on which any grow depends. High temperatures due to poor ventilation may cause heat stress too.

Adjusting Lights

Make no mistake: grow lamps can emit serious amounts of heat as a by-product of the light they emit. In fact, a lamp’s heat can be just as harmful as the sun at noon on a sweltering day. On top of that, growers are often more aware of the weather outside than of the conditions in their grow room or tent. Be sure to keep track of temperatures and try to keep them between 20 and 25°C. In the flowering phase, you’ll want to try and keep temperatures below 28°C. Remember, though, that these are average temperatures across the entire grow space. You can monitor heat using a regular thermometer, but remember that it gets hotter the closer you get to the light source. And it just so happens that cannabis plants tend to grow towards the light…

If you notice the symptoms of heat stress manifest mainly around the top leaves of the plant, lighting is your prime suspect. If you see the signs all over your plants, it’s probably the general temperature in the room.

If you have enough room, hoist up your lighting goes a long way towards protecting your indoor cannabis grow from heat. You could also try grow techniques that aim to keep plants short and compact, such as Screen Of Green or Mainlining, for example.

Also keep in mind that led lights emit less heat than most other systems. In addition, they’re usually the cheapest option as well as being more eco-friendly in terms of energy use.

Circulation

Grow rooms and tents cool down by keeping warm air circulating, and by making sure that warmed-up air is refreshed with cool air from the outside. That means protecting indoor cannabis from heat can be a matter of putting up enough fans for ventilation plus adequate exhaust capacity. Do make sure any exhaust fans have filters installed, though, to prevent odour problems and related issues.

Cannabis Strains Capable Of Protecting Themselves Against Heat

At the end of the day – hot days included – cannabis is a tough and resilient plant species, well-equipped to cope with warm weather or hot grow rooms. Still, some strains can handle heat better than others.

Even though most modern strains are hybrid crossing between indica and sativa genetics, sativa-dominated strains tend to handle heat slightly better. This is largely due to their tropical origins, since they evolved to thrive in warm areas near the equator.

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Still, a cannabis seed’s genetic background is never a guarantee for its heat protecting capacity. Of course, it always helps to order your seeds from a high-quality supplier. You’ll find our best sativa-dominant strains in our online catalogue, but don’t let anyone discourage you from growing indica instead. Or perhaps a robust sativa autoflower like Dynamighty is a practical alternative for you? No matter what genetics you pick, at least now you know that protecting cannabis against heat ain’t no sweat if you have the right knowledge handy!