Every cannabis cultivator needs to be able to interpret the signals their weed leaves send out. If you can quickly understand and treat your plant’s health issues, you’ll enjoy robust plants and fantastic yields. Here, we break down each problem expressed by the leaves of your weed plants, and teach you how to treat and prevent them accordingly.
Functions of the weed leaf
As it is with many other plants, leaves are key components of a cannabis plant’s life support system. The green pigment chlorophyll allows leaves to act as solar panels. This sunlight-gathering role, as you probably know, is essential to photosynthesis.
The underside of the leaves are covered in tiny stomata, microscopic holes that open and close like a door. Carbon dioxide goes in, oxygen and water go out. The leaves can also absorb nutrients to feed the cannabis plant in a process known as foliar feeding.
Types of cannabis leaves
There are three main types of cannabis. These are often officially lumped together under the name Cannabis sativa L.; for practical purposes, though, it helps to make distinctions between sativa, indica, and ruderalis plants.
That being said, most cannabis you encounter these days is a hybrid of two or three of these types. Thus, what you will typically see in your grow room are weed leaves that express a mix of traits. There can be 3, 5, 6, 9, or 11-point leaves, and they come in shapes ranging from thin and slender to wide and round.
Sativa leaves are long and slender-fingered, with some developing as many as 13 fingers. Usually, sativa plants will have a lighter, lime green shade, indicating a relatively low amount of chlorophyll. It is believed that reduced chlorophyll is partly responsible for the longer flowering period of sativa strains.
Indica leaves are short and wide, typically with 7–9 fat fingers. These leaves are even larger when they belong to the heavier indicas of Afghan origin. Healthy indica leaves are marked by their darker, deeper shade of green. This is a sign of the leaves containing more chlorophyll, which is believed to accelerate the bloom cycle of indica varieties.
Ruderalis leaves are quite thin and only develop 3–5 slender fingers. Most growers describe them as comparable to the leaves of young sativa plants, both in shape and colour. These plants are special, though, as they have evolved to flower independent of the hours of light they receive.
Fan and sugar leaves
Aside from the leaf types corresponding to sativa, indica, or ruderalis cannabis, we can also differentiate leaves depending on where they’re found on the plant. The largest leaves on the cannabis plant, with the typical fingered shape, are called fan leaves. The other type of leaves, which are small and nestled within flowers, are called sugar leaves.
The fan leaves, as we mentioned, are the large leaves that develop during the vegetative growth phase. They function like solar panels, absorbing light and converting it into energy for the plant to grow. These leaves can also serve as emergency storage for certain nutrients like nitrogen. If the plant can’t get them from the soil, it can draw stored nutrients from the leaves. When this happens, as we’ll explain in detail soon, the leaves will start to turn yellow.
The fan leaves contain only trace amounts of THC, CBD, and other cannabinoids.
The sugar leaves can be found nestled within and extending from the buds. Their surface is covered by a “frosting” of white trichomes, which is the inspiration for their name. Essentially, the function of sugar leaves is to give structure to the buds so they stay together.
Sugar leaves are rich in cannabinoid-loaded trichomes, but can introduce a harsh taste when smoked. As a result, cultivators normally trim them from the buds. Although less optimal for smoking, sugar leaves are ideal for making hash or cannabutter.
Reading the signs of cannabis plant health issues
What sets experienced cultivators apart from beginners is the former’s ability to “read” their cannabis plants. Leaves tend to send strong signals to the cultivator, informing them about the health and well-being of the plant. In order to fix growing troubles quickly, it’s important for the cultivator to know how to read the signs.
What does an indica leaf look like?
First named in 1785 for a kind of marijuana that grows in India, the indica leaf is short and stout, possessing between seven and nine wide, finger-like structures.
Steven Somoza of Hydroponics, Inc. in Los Angeles, California, has more than eight years of cannabis cultivation experience and shared with Weedmaps, “Indica-dominant strains tend to have a stocky bush-like appearance, typically developing fat and wide leaves.”
The indica leaf’s short stature makes it a good choice of cannabis to grow indoors. You can spot an indica leaf if you pay attention to color, as indicas are a deep shade of green, which signifies a high chlorophyll content. Pure indica strains may include Hindu Kush, Purple Kush, and Afghani Kush, but pure strains of any kind are rare and challenging to find.
What does a sativa leaf look like?
In contrast to indica plants, sativa plants fare better outdoors due to their exceptional height (up to 12 feet). The slender sativa leaf also has more fingers than the indica leaf, sometimes as many as thirteen.
In contrast to indica leaves, sativa-dominant genetics “typically grow lengthy, can take longer to mature, and develop skinnier leaves” according to Somoza.
Besides size and finger differences, you can distinguish between an indica and a sativa leaf by the latter’s lighter shade of green. Pure sativa strains may include Jack Herer, Panama Red, and Durban Poison, but connoisseurs debate whether these strains are truly pure or simply sativa-dominant. Jack Herer, for example, may be 80% sativa and 20% indica depending on the plant.
What does a ruderalis leaf look like?
Originating in Russia and Central Asia, ruderalis is a separate species of autoflowering cannabis that grows in the wild. It is shorter than sativa and indica, sometimes only reaching a foot or two tall. Ruderalis leaves are thin and each plant only exhibits three to five delicate fingers. Russian Auto CBD is one of the only known pure ruderalis strains, as most that contain this species are hybrids.
What is a hybrid cannabis leaf?
Finding pure marijuana strains is no easy task these days and hybrids are ubiquitous. Hybrid leaves tend to be harder to identify as they may favor their parent strains in different ways. White Widow, Cannatonic, Blue Runtz , Gorilla Glue, Chemdawg, and Sour Diesel are some of the many popular hybrid weed strains available.
Why is it important to know the difference between cannabis leaves?
The ability to distinguish between cannabis leaves, particularly the indica and sativa varieties, is a useful tool for both new and seasoned growers. For starters, knowing how to read cannabis leaves gives cultivators insight into how well (or how poorly) their plants are flourishing.
Somoza elaborated, “A new grower must learn to ‘read’ these leaves as just one of many ways to get a feel for the plant’s health. Most deficiencies and problems will show at the leaves with quick enough onset: drooping, tip-curling, leaf spotting, pest damage, etc.”
To assess the health of your cannabis plants, do a quick, daily check-up to see if any of those signs are present. Somoza also advised, “Get in the habit of rubbing your leaves and turning over and inspecting leaves when you defoliate.”
Keeping a watchful eye on leaves during all stages of growth can help familiarize you with what makes a healthy cannabis plant and what constitutes a struggling one.
What can I do with cannabis leaves?
Raw cannabis leaves are versatile and valuable, so be mindful the next time you trim them from your plants. First, let’s identify the two types of cannabis leaves that you’ll encounter whether you’re growing an indica or sativa-dominant strain:
Sugar leaves: Coated in white trichomes, sugar leaves are small and grow from the buds. Somoza explained the process of sugar leaf development this way: “As cannabis matures, the bracts or buds of the plant will swell and develop ‘sugar’ that will grow and fall on surrounding leaves. These sugar leaves are loaded with cannabinoids and are still useful when trimmed off during or after harvest.”
As a rule of thumb, indica strains produce more resin glands which yield a greater amount of trichomes. Therefore, indica strains tend to have more sugar leaves than sativa strains.