Cannabis fan leaves: what they are and how to use them

Cannabis fan leaves act like solar panels for cannabis plants, helping to fuel vegetative growth. And while many growers simply discard their fan leaves post-harvest, they can actually serve a wide variety of purposes. In this article, we'll teach you all about the importance of cannabis fan leaves, how to deal with any issues they may present during the grow cycle, and, finally, multiple ways to use them after harvest.

WHAT DO CANNABIS FAN LEAVES LOOK LIKE?

Fan leaves can easily be told apart from so-called sugar leaves by their size and location. Whereas sugar leaves are small, single-finger leaves that grow among cannabis flowers, fan leaves are the big, broad leaves that grow directly from a plant's stem and branches. Furthermore, while sugar leaves contain their fair share of crystalline resin—hence the name—fan leaves contain very little resin and cannabinoids, and as such are often discarded by most growers after harvesting the buds.

Cannabis fan leaves can also tell you a fair bit about your plant's genetics. Sativas and sativa-dominant hybrids, for example, tend to develop large, bright green leaves with slender fingers, while indicas and indica-dominant hybrids have distinctly broad, dark-green leaves. And finally, Cannabis ruderalis, which is responsible for endowing strains with the autoflowering trait, has small, distinct leaves with 3–5 stubby fingers—which is in contrast to the 5–7 or more fingers on sativa and indica leaves.

WHY ARE FAN LEAVES IMPORTANT?

Fan leaves allow the cannabis plant to soak up plenty of sunlight and turn that energy into food to fuel growth (i.e. photosynthesis). During the vegetative stage, big, green fan leaves are a very good sign of healthy, happy plants.

On the other hand, drooping, discoloured, or damaged leaves are usually a sign of a watering issue, nutrient deficiency, or the presence of pests/pathogens. So keeping an eye on the state of your leaves can give you a good indication of your plant's overall health.

During the flowering stage (particularly the last few weeks of flowering), it is natural for cannabis fan leaves to turn yellow. We'll look at the different causes of yellow leaves in more detail below.

WHY SHOULD I REMOVE FAN LEAVES?

Fan leaves are vital for cannabis plant growth and development, so removing them can seem counterintuitive. However, methodically removing leaves—a practice known as defoliation—is actually common among weed growers, as it can help to:

• Stimulate new growth
• Better distribute plant energy
• Open up a thick canopy to promote airflow and better light penetration

How much or little you choose to defoliate will depend on personal experience and preferences, as well as the genetics of a given strain. If you're growing tall, stretchy sativas with fewer overall leaves, for example, you might choose to defoliate less than if you're growing stocky, bushy indicas. If you're new to the process, start by defoliating just 1–2 times during veg, and one final time in the first weeks of flowering.

TOP TIPS FOR DEFOLIATING CANNABIS

• Which fan leaves to remove?

Start by removing damaged or discoloured leaves first (a few discoloured leaves is pretty normal, but many yellow leaves can be a sign of nutrient problems, pH issues, or other forms of stress). Next, remove any leaves that are blocking light from key bud sites or preventing air from flowing throughout the plant.

• How many leaves should I remove?

"Slow and steady wins the race" is the golden rule when defoliating. We recommend never removing more than 10–15% of a plant's foliage in a single defoliation session, as this could cause unwanted stress.

• When can I defoliate?

We recommend defoliating chiefly during the vegetative stage, as well as in the first week or so of flowering. Remember that fan leaves removed during flowering won't grow back, and removing too many can throw off the plant's energy balance, stunting bud development in turn.

CAN I TRIM FAN LEAVES ON AN AUTOFLOWER?

Autoflowering cannabis strains have very short veg phases (typically 3–4 weeks, depending on the strain). To avoid stunting their growth during this short time, most auto growers avoid high-stress training or defoliating.

While we generally agree that autoflowers shouldn’t be subjected to excessive stress, gently defoliating them shouldn't be a problem. In fact, we recommend removing any unhealthy foliage from your autoflowers to help direct their limited resources to developing healthy new leaves and bud sites.

WHY DO FAN LEAVES TURN YELLOW?

Fan leaves can turn yellow for a number of reasons. The first and least concerning cause is senescence, or, simply put, old age. It is normal for vegging cannabis plants to naturally discard a few old leaves to focus their limited energy on developing new foliage.

During flowering (especially the final weeks), don't be surprised to see a large number of fan leaves turn yellow; this is completely natural, and a sign that the plant is using up all its stored energy as it approaches the end of its life cycle.

However, yellow fan leaves can also be a sign of stress. If a plant starts developing lots of yellow foliage during veg or the earliest stages of flowering, this could be a sign of:

• Nitrogen deficiency
• Nutrient lockout (commonly caused by pH problems)
• Overwatering or underwatering
• Hot temperatures

Unfortunately, yellow fan leaves are a common symptom of many different cannabis ailments. Identifying the exact cause takes time, patience, and the process of elimination.

WHY ARE MY FAN LEAVES CURLING DOWN?

Just like yellowing leaves, curling fan leaves are another key sign of stress. If you notice a plant's leaves curling down, look into the following issues to quickly identify and address the problem:

• Overwatering: Rookie growers often run into this problem, which can lead to more serious problems with pests and fungi. Luckily, fixing overwatering is simple—stop watering your plants, let the soil dry out completely, and generally avoid watering until the top few centimetres of soil has fully dried out.
• Pests: Aphids and mites both love living and feeding on the underside of cannabis leaves. If a plant's leaves are curling downward and feel dry to the touch, inspect their undersides closely. If you find aphids or mites, use the appropriate means to kill them, and remove any damaged or affected foliage.
• Poor soil quality: Poor soil that's lacking nutrients, is too "hot" (nutrient-rich), or doesn’t have the right pH will stress your plants and stunt their growth. If you're not overwatering and your plants are free of pests, but your fan leaves are still curling downward, check your soil to verify it has the correct balance of nutrients and pH for the given strain (tip: most cannabis cultivars like soil with a pH of 6.0–6.5).
• Wind or light burn: Cannabis is a sun-loving plant that needs fresh, circulating air in order to grow properly. Harsh light from artificial grow lights or strong winds, however, can inflict significant stress, causing leaves to curl down in an attempt to minimise their exposure to these conditions.
• Over-fertilisation: This is another problem rookie growers commonly run into. While fertiliser is of course important for growing healthy, strong plants, over-fertilising can stress your specimens and cause symptoms such as leaf curling. This is known as nutrient burn or "nute burn".
• Temperature/humidity issues: Generally speaking, cannabis likes warm temperatures and balanced relative humidity. Hot, cold, or overly humid conditions can interfere with the healthy growth of a cannabis plant, causing their leaves to droop and curl. If growing indoors, make sure to keep the temperature and RH optimal; if growing outdoors, try to bring your plants indoors during extended droughts, storms, or when the temperature drops.

WHAT TO DO WITH CANNABIS FAN LEAVES

Many growers simply throw their fan leaves in the trash or on the compost pile. Fortunately, more and more growers are interested in preserving their fan leaves rather than simply throwing them away. Below, we share some potential uses for cannabis fan leaves, and some tips to help you get the best out of them.

CAN LEAVES BE CLONED?

This is a common question among growers, but unfortunately, it is not possible to clone a cannabis fan leaf.

Clones are taken from a cannabis plant's stem or branches, which can root and then grow into a full-fledged plant. While grow forums are rife with pictures of rooted fan leaves, these leaves won't grow into full plants, meaning they won't actually serve as clones. If you're interested in preserving a cannabis plant and can't clone it (for whatever reason), re-vegging might be a more feasible option for retaining its genetics.

DO CANNABIS FAN LEAVES CONTAIN CANNABINOIDS?

Compared to buds and sugar leaves, cannabis fan leaves contain very low concentrations of cannabinoids and terpenes—the phytochemicals that give cannabis its unique effects.

Remember that cannabinoids (THC, CBD, etc.) and terpenes (myrcene, pinene, etc.) are found in the thick resin that coats ripe cannabis flowers. Fan leaves, in general, have little to no resin, and therefore contain only trace amounts of these compounds.

However, don't let that be reason enough to throw out your fan leaves. Cannabis leaves might not get you high, but as you'll see below, they have many other uses.

THE NUTRITIONAL VALUE OF FAN LEAVES

Juicing raw leaves has become ever more popular, especially in areas where using and/or growing cannabis is legal. According to the United Patients Group, raw cannabis is extremely nutritious, containing fibre, calcium, and iron, antioxidants, omega-3 and 6 fatty acids, amino acids, and a wide variety of vitamins and minerals.¹

If you're interested in harnessing the nutritional benefits of raw, fresh leaves, consider adding them to salads, juices, or herbal teas.

USING FAN LEAVES IN SALADS AND SMOOTHIES

Cannabis fan leaves make a great addition to any fresh salad. While their taste might take some getting used to (the leaves are fairly bitter), a rich salad dressing goes a long way toward making fan leaves more palatable. Pairing the bitterness of raw cannabis with sweet ingredients such as ripe tomatoes, bell peppers, and roasted veggies also works great.

If eating raw fan leaves isn't for you, try adding them to your favourite smoothie. Combining weed leaves with spinach, chard, apples, and cucumbers, for example, makes for a superb green smoothie.

MAKE CANNABIS TEA

One of the best uses for fresh cannabis leaves is making tea. Steeping a few leaves in hot water can make for a relaxing, flavourful drink with a distinct flavour, somewhat comparable to sage tea. Consider combining weed leaves with chamomile, green tea, boldo, or mint, and sweetening with a teaspoon of honey for an even tastier brew.

MAKE YOUR OWN LOTIONS AND BALMS

Cannabis topicals have become enormously popular. With that in mind, another great way to use leftover fan leaves from your harvest is to make your own cannabis balms and lotions.

The simplest way to make a topical using fan leaves is to steep them in hot coconut oil for 1–3 hours. You can do so by adding coconut oil and fan leaves into a heatproof glass jar and steeping the mixture in a bain-marie.

CAN RABBITS EAT CANNABIS FAN LEAVES?

While cannabis fan leaves only contain trace amounts of cannabinoids, we really don't recommend feeding them to herbivorous pets, including rabbits. Animals are much more sensitive to cannabis than humans, and may experience psychoactive effects from eating the leaves.

HOW TO STORE CANNABIS FAN LEAVES

If you've just harvested a few marijuana plants and aren't ready to use all of your fan leaves at once, the best way to store them is by freezing them in a ziplock bag. You can then simply take out a handful of leaves every time you want to use them in a recipe (keep in mind that thawed leaves are quite soggy, and therefore won't go well in a salad).

Alternatively, you can also dry cannabis leaves and store them in jars, similar to how you would store dried cannabis buds (note that you don't need to cure cannabis leaves before using them). Then, you can indulge whenever you like!

References:

1. Malanca, J. Top 8 Health Benefits of Consuming Raw Cannabis. United Patients Group. 2017. Available at: https://unitedpatientsgroup.com/blog/top-8-health-benefits-of-consuming-raw-cannabis/