Cannabis Seed Anatomy

Come inside to get to know every aspect of the cannabis plant, from terpene-producing trichomes to photosynthesising fan leaves and everything in between! Knowing the anatomy of a marijuana plant is important for any grower. Learn to identify the different parts of a cannabis plant from the experts at Leafly. To know more about the different parts of the cannabis plant will facilitate cultivation and help us achieve better results. In this post we explain t

Cannabis Plant Anatomy: From The Bottom To The Top

Without a doubt, cannabis claims the title as one of the most beautiful plants on Earth—from its glittering trichomes and signature leaves to its complex root system. Many growers frequent their grow rooms just to stand in awe at what grows before them.

Although the flowers get most of the attention—and rightly so—every part of this complex species has a critical and interesting function. As a cultivator, it helps to familiarise yourself with the anatomy of the cannabis plant. In doing so, you’ll develop an eye for what your plant requires, what it needs less of, and when to harvest.

Explore our in-depth guide below to see the cannabis plant like never before.

MYCORRHIZAE

Although not genetically part of the cannabis plant, mycorrhizae form a mutually beneficial relationship with cannabis roots that helps both species survive and thrive. These fungi appear all throughout nature and form a fascinating symbiotic relationship with up to 90% of plant species.

FUNCTION

Mycorrhizal fungi participate in a give-and-take relationship with cannabis plants. These species form networks of thin, hair-like filaments in the soil—known as mycelium—and produce enzymes to break down organic matter.

After liberating nutrients from the substrate, the mycelium uptakes and shuttles them around to plants. Because cannabis roots aren’t capable of this impressive function themselves, they have to “bargain” with the mycelium to access these nutrients. Luckily, plants produce sugars during photosynthesis, and transport many of these molecules down into the roots. Here, they swap these energy-rich exudates for the nutrients they need to fulfil important physiological functions.

Mycorrhizae ultimately act as an extension of the root system. Not only do they break down organic matter to release nutrients, but they also transport these important molecules from areas plants could otherwise not reach. Ultimately, mycorrhizal fungi play a fundamental role in plant nutrition and soil biology and chemistry.

LOCATION

This fusion between plant and fungi occurs in the rhizosphere, or root zone. The mycelium forms a sheath-like structure around the root tip that surrounds plant cells in the root cortex. Threads of hyphae—individual strands of mycelium—extend out into the soil where they break down organic matter and even connect one plant to another, forming a biological internet.

HOW TO BOOST MYCORRHIZAE PRODUCTION

Mycorrhizal fungi exist naturally in many different types of soil. However, there are numerous different species. To make the most of this synergistic relationship, introduce tried and tested mycorrhizal fungi products when planting or transplanting.

Marijuana plant anatomy and life cycles

The cannabis plant has several structures, many of which we can find on any ordinary flowering plant species. Cannabis grows on long skinny stems with its large, iconic fan leaves extending out from areas called nodes.

Cannabis really stands out in its flowers—or buds—where unique and intricate formations occur: fiery orange hairs, sugary crystals, and chunky buds enveloped by tiny leaves.

The life cycle of a marijuana plant

There are 4 stages in the life cycle of a marijuana plant:

  • Germination (3-10 days): When the seed sprouts and pops out of the soil
  • Seedling (2-3 weeks): After germination, when the plant develops its first cotyledon leaves
  • Vegetative (3-16 weeks): The immature or juvenile stage, when a cannabis plant grows its stalks, branches, stems, and fan leaves
  • Flowering (8-11 weeks): When a weed plant starts producing buds

Parts of the cannabis plant

Cannabis seeds

Seeds are produced in female cannabis plants and carry the genetics of a male and female. Seeds need to germinate to sprout and will grow a taproot, which will become the main root that anchors the plant.

Cotyledon leaves

These are the first leaves to grow from the seed after germination. They usually come in pairs, and seeing them is a sign of successful germination and that your plant is on its way to growing healthy and strong.

Cannabis roots

The roots grow down from the main stalk of the plant into the soil. When growing from a seed, the main root is called the “taproot.” Roots are the lifelines of a cannabis plant, pulling water and oxygen into the plant so it can grow healthy and strong.

Mycorrhizae, a beneficial fungus, can be added to soil to improve root systems.

Marijuana plant stem

The main stem, or stalk, of a cannabis plant grows straight up from the root system and supports all lateral branches. The stem gives a plant structure and stability.

Often, growers will top, or cut off, the stem after about five nodes, which forces the plant to grow out laterally more, creating more bud sites.

Branches

Branches grow out of the main stem and support fan leaves and buds. Growers often train a cannabis plant by topping branches to create more bud sites.

A node is a point at which a branch grows off of the main stem, or one branch from another branch. Fan leaves and buds can grow on some nodes, but not necessarily all.

When determining the sex of a cannabis plant, pre-flowers, or the beginnings of male and female sex organs, will appear at the nodes.

The space between nodes is called “internodal spacing” and will give you a sense of whether a plant will grow tall or short.

Check out Johanna’s full video series on how to grow weed on Leafly’s YouTube .

Fan leaves

Fan leaves are the large, iconic leaves of the cannabis plant. They capture light for the plant and typically have little-to-no resin and are usually discarded when trimming.

Sugar leaves

Sugar leaves are the small, resin-coated leaves that buds form around. Sugar leaves are usually saved as “trim” during harvest and can be used for pre-rolls, extracts, and other cannabis products.

Flowers

Also known as “buds,” the flowers of a cannabis plant are the fruits of your labor. They contain the cannabinoids and terpenes that get you high or offer health benefits. Flowers only grow on female cannabis plants and must be dried before consumption.

A cola, also called a “bud site,” refers to a cluster of buds that grow tightly together. While smaller colas occur along the budding sites of lower branches, the main cola—sometimes called the apical bud—forms at the top of the plant.

Bract and calyx

A bract is what encapsulates the female’s reproductive parts. They appear as green tear-shaped “leaves,” and are heavily covered in resin glands which produce the highest concentration of cannabinoids of all plant parts.

Enclosed by these bracts and imperceptible to the naked eye, the calyx refers to a translucent layer over the ovule at a flower’s base.

Stigma and pistil

The pistil contains the reproductive parts of a flower, and the vibrant, hair-like strands of the pistil are called stigmas. Stigmas serve to collect pollen from males.

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The stigmas of the pistil begin with a white coloration and progressively darken to yellow, orange, red, or brown over the course of the plant’s maturation. They play an important role in reproduction, but stigmas bring very little to the flower’s potency and taste.

Trichomes

Despite their minute size, it’s hard to miss the blanket of crystal resin on a cannabis bud. This resin is secreted through translucent, mushroom-shaped glands on the leaves, stems, and calyxes.

Plants originally developed trichomes to protect against predators and the elements. These clear bulbous globes ooze aromatic oils called terpenes as well as therapeutic cannabinoids like THC and CBD. The basis of hash production depends on these trichomes and their potent sugar-like resin.

Male vs. female marijuana plants

Cannabis is a dioecious plant, meaning it can be male or female, and the male and female reproductive organs appear on different plants. What’s in your stash jar now are the flowers of a female marijuana plant.

Female plants produce the resin-secreting flower that is trimmed down into the buds you smoke, and males produce pollen sacs near the base of the leaves. Male plants pollinate females to initiate seed production, but the buds we consume come from seedless female plants—these are called “sinsemilla,” meaning “seedless.”

Growers can ensure the sex of their plants by growing clones or the genetically identical clippings from a parent strain. Feminized seeds are also made available through a special breeding process.

How to determine the sex of a marijuana plant

Cannabis plants show their sex by what grows in between their nodes, where leaves and branches extend from the stalk. Pollen sacs will develop on a male plant to spread seeds and stigma will develop on a female to catch pollen. You can see these differences weeks before they actually start serving their purposes in the reproduction cycle. These are known as “pre-flowers.”

Pre-flowers begin to develop four weeks into growth, but they may take a little longer depending on how quickly the sprouting phase occurs. By the sixth week, you should be able to find the pre-flowers and confidently determine the sex of your plant.

Examine the nodes of the plant and look for either the early growth of small sacs on a male, or two bracts on a female, which will eventually produce the hair-like stigma.

Female marijuana plants

Females are the prizes of cannabis plants—they are the ones that grow the buds that we all know and love. Anytime you see a picture of a cannabis plant with buds, you are looking at a female plant.

Female cannabis plants receive pollen from males to produce seeds, which will carry on the genetics of both plants to the next generation.

However, cannabis is primarily cultivated for buds, not seeds, so the practice of growing sinsemilla, or “seedless” cannabis, is prevalent today: Females and males are grown separately, or males are even discarded, to prevent pollination. This allows female plants to focus their energies on bud production instead of seed production.

Males and females are usually only pollinated when crossbreeding plants or creating new strains.

Early signs of a female cannabis plant

A few weeks into the flowering stage, sex organs will appear on a cannabis plant at a node, between the main stem and a branch. The female reproductive organs look like an oval with white hairs coming out of them, which are pistils.

If you’re not quite sure, let the plant grow for another week or so and check again.

Male marijuana plants

Male cannabis plants grow pollen sacs instead of buds. Male plants are usually discarded because you don’t want them to pollinate the females, which will produce seeds—no one wants to smoke buds with seeds in it.

Males are important in the breeding process, but that is generally best left to expert breeders. When pollinating females, males provide half of the genetic makeup inherited by seeds.

Because of this, it’s important to look into the genetics of the male plants. Their shape, rate of growth, pest and mold resistance, and climate resilience can all be passed on to increase the quality of future generations.

Early signs of a male cannabis plant

To spot a male weed plant, check the sex organs at a node, between the main stem and a branch. The male organs will look like a round ball—these will develop into pollen sacs.

If you’re not sure if it’s a male or female yet, wait a week or so and check again. At this early stage there isn’t much risk of a male pollenating your crop.

What can I do with male cannabis plants?

Male plants can also be used for:

  • Hemp fiber—males produce a softer material, while females produce a coarser, stronger fiber. The soft fiber from males is more desirable for products like clothing, tablecloths, and other household items.
  • Concentrate production—males do have some THC and can be psychoactive, but much less so than females. Small amounts of cannabinoids can be found in the leaves, stems, and sacs, which can be extracted to produce hash and other oils.

What are hermaphrodite cannabis plants?

The rare hermaphroditic plant contains both female and male sex organs. These plants can sometimes self-pollinate, but this is typically bad as it will create buds with seeds and also pass on hermaphroditic genes.

“Herming out,” as some call it, is something that generally happens when a plant becomes excessively stressed. Some stressors include:

  • Plant damage
  • Bad weather
  • Disease

There are two types of hermaphrodite cannabis plants:

  • A plant that develops both buds and pollen sacs
  • A plant that produces anthers, commonly referred to as “bananas” due to their appearance

While both result in pollen production, true hermaphrodite cannabis plants produce sacs that need to rupture; anthers are exposed, pollen-producing stamen.

Because this occurs when cannabis is under stress, it’s important to monitor plants after they have been exposed to stressors: indoors, high temperatures or light leaks are often the cause; outdoors, a snapped branch might be repaired and then turn into a hermaphrodite.

The other primary cause of hermaphrodite plants lies in its genetics—a plant with poor genetics or a history of hermaphroditic development should be avoided to protect your garden. If you notice any pollen sacs or anthers at any point, remove the plant from your garden immediately to prevent pollination of female plants.

Marijuana plant anatomy FAQ

What are the first leaves called on a cannabis plant?

Flowering plants, including cannabis, have baby cotyledon leaves which appear shortly after the seed germinates, or sprouts. These embryonic leaves help the plant get started.

How soon can you tell if a cannabis plant is male or female?

Sex organs will appear on a plant within 2-3 weeks of flowering.

When do male cannabis plants pollinate female plants?

Male pollen sacs usually open up and spread pollen via the air 4-6 weeks after they begin flowering.

How does weed grow buds?

When cannabis plants experience a reduction in light, either after the summer solstice when growing outdoors, or manually when growing indoors, they will begin the flowering stage, when buds are produced. Flowering typically takes 7-11 weeks, depending on the strain.

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Anatomy of the Cannabis plant

When it comes to cannabis, the part of the plant that gets all the attention is naturally the bit we’re all growing for: the flowers. But while it’s easy to be enamoured with the beautiful frosty flowers we shouldn’t overlook the rest, because behind the bud there’s a whole plant, with all its component parts, each playing an essential role in bringing us our precious harvest.

Here at Alchimiaweb we strongly believe that the more we know about our favourite plants, the more success we’ll have cultivating them, and the happier we’ll be with the results! For these reasons here we’re going to take a closer look at the cannabis plant and identify all the different elements of its anatomy to help you get to know this wonderful plant a little bit better.

1, male flower, enlarged detail; 2, pollen sac; 3, pollen sac; 4, pollen grain; 5, female flower with bract; 5, female flower, bract removed; 6, female seed cluster, longitudinal section; 7, seed with bract; 8, seed without bract; 9, seed without bract; 10, seed cross section; 11, seed longitudinal section; 12, seed without hull (Franz Eugen Köhler 1887)

The Cannabis seed

For most of us, our introduction to cultivation comes when we buy or are gifted some cannabis seeds for the first time, so let’s set out on our examination of cannabis anatomy starting with the seed.

A healthy, mature cannabis seed will be well-rounded in shape with one pointed end and one flat end. They have a tough outer casing that is rigid to the touch, preventing the seed from being easily crushed. A seam separates the two halves of the shell (also known as the hull or pericarp) and is where the seed opens during germination.

Depending on their genetics, seeds can vary greatly in size, from really tiny (800 seeds per gram) to absolutely massive (15 seeds per gram). In mature seeds the outer shell should be covered with attractive dark markings known as “tiger stripes” which, like snowflakes, are unique to each seed and are in reality a thin layer of cells coating the seed and can be rubbed off easily, revealing the true tan/beige colour of the seed beneath.

Detailed view of a cannabis seed

Inside the seed we will find the embryo of the plant, everything needed to start a new life, dormant until the right conditions of moisture and warmth are met. We have the root, or radicle as it’s known while still in the seed, the cotyledons, those first, fat, rounded embryonic leaves containing the seed’s food reserves for early development. Cannabis is a “dicot” plant, meaning it has two cotyledons. Situated in between the cotyledons, surrounded by the first two true leaves is the apical tip, the point from which the plant will continue growing once germinated.

Roots

When we germinate a cannabis seed, the first thing that emerges from the opened seed will be the tap root which will begin to grow downwards, seeking out moisture and nutrition and colonising the substrate. The root system has three main purposes, not only does it anchor the plant in the substrate, it provides it with water and the nutrients, and it also acts as storage for sugars and starches produced by photosynthesis. It’s hard to overstate the importance of the roots in cannabis cultivation, they really are the foundation upon which everything else is built, without healthy roots we won’t harvest beautiful flowers!

Roots themselves can be classified into three types. Firstly the tap root, which is the principal component of the root system, the subterranean counterpart to the plant’s main stem, pushing vertically downwards and shooting off branches as it grows. These branches are the second type, the fibrous roots, which branch off from the tap root, extending outwards to form an underground network approximately the same size as the aerial part of the plant. A third type of roots are known as adventitious roots, these are the thick roots that sometimes sprout from the stem just above ground. These are the roots that make it possible to reproduce plants by taking cuttings and cloning them.

Adventitious root growing from the stem of a clone

Cannabis plants grown from seed will start life with a tap root system that develops into a fibrous root system, while clones don’t have a tap root, starting instead with adventitious roots before developing a fibrous root system. In all cases, a root system needs an adequate balance of moisture and air to be healthy and if care and conditions are right we will be able to see thick, bright white roots with plenty of fine hairs when we transplant.

The root crown

The part of the plant where the roots and stem join is called the root crown, or sometimes collar, or neck. This is a vital part of the plant, the dividing line between upward and downward growth, where the vascular system switches from roots to stem, and one of the places in the plant where most cell division takes place.

The root crown is naturally situated very close to the surface, where aeration is at its most, however some growers will transplant with the crown buried well below the surface, which encourages adventitious roots to sprout from the buried section of stem. It’s good way to deal with those leggy seedlings that stretched to get to the light and ended up too tall.

Stem and nodes

The stem of the cannabis plant is the part responsible for keeping the plant upright and for supporting the weight of the plant. It contains the vascular system which works to carry moisture and nutrients from the roots to the leaves via xylem cells, and to transport the sugars and starches produced via photosynthesis around the plant for use or storage via the phloem cells. Phloem is otherwise known as bast, the part of the cannabis or hemp plant that is traditionally harvested for fibre to make rope, canvas etc.

Cross section of stem showing a node

The stem, which can sometimes be hollow, is divided by nodes where the lateral branches begin, with the space between them being known as the internode. Seedlings will begin by growing opposite pairs of nodes and leaves but as time passes the nodes will start to grow alternately, sign the plant is mature and ready to flower.

Taller, stretchier Sativa plants will have a larger internode spacing than squat, compact Indica varieties, although environmental factors can also influence internode space. The nodes are where the first flowers appear (pre-flowers), so it’s the first place growers look when trying to determine the sex of plants grown from regular seeds. The small, narrow spear-like leaf growing at each node is called the stipule, and shouldn’t be confused with pre-flowers.

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Nodes are one of the parts of the cannabis plant where most growth happens and most hormones are produced, for this reason we always cut clones with at least one node to be planted below ground in the substrate, so it can produce auxins (rooting hormones) to begin root development in the undifferentiated meristem cells of the node.

Leaves and petioles

Cannabis leaves are palmately compound (shaped like the open hand, with multiple parts), with anything from 3 to 13 veined, serrated leaflets or fingers. Indica varieties will generally have wider and shorter leaflets of a lush dark green colour, but fewer in number, while Sativas will have longer, narrower leaflets and can be of a lighter green shade. Of course, cannabis is a hugely diverse genus and there are exceptions to this rule, most notably the Ducksfoot variety, with its webbed leaves. Autoflowering varieties will tend to have smaller leaves, with the shape depending on the individual genetics, but as a general rule leaning more to the Indica side.

Leaf and structure comparison of the different cannabis species

A cannabis plant will have large and small fan-type leaves, which we remove and dispose of at harvest time, and also sugar leaves, which are the small, resin-covered leaves that protrude from the bud. These will either be trimmed away and kept aside for resin extraction, or simply left on the bud and smoked with the flowers.

Leaves from two different hybrids

As a seedling grows, each set of leaves has an increasing, odd number of leaflets, so the first set of leaves above the cotyledons will almost always have a single leaflet, the second pair will have three, the third will have five and the fourth will have seven leaflets, and so on until the plant reaches the usual number as dictated by its genetics.

The leaflets join at the point known as the rachis, from where they attach to the stem or branch by a leaf-stem known as the petiole. Petioles can be of varying length depending on the variety and can naturally vary in colour from green to dark purple, although in normally green plants a purple petiole can often be a sign of a phosphorous deficiency.

The fan leaves function both as solar panels and air conditioning for the plants, with the darker green upper side of the leaf producing energy via photosynthesis and the underside regulating internal processes via stomata, tiny pores that absorb the CO2 needed for photosynthesis and at the same time release water and oxygen. The stomata will close at night to conserve moisture and during the day will respond to heat and humidity levels, opening and closing to constantly balance internal moisture levels with external environmental conditions and keep metabolic functions working.

Flowers

Cannabis is dioecious, meaning the male and female reproductive organs are on different plants. Unless we’re planning on doing some home breeding and making seeds, we won’t be growing any male plants to full maturity, but it’s important to be able to identify them, even if we’re growing exclusively from feminised seeds, just in case.

Female pre-flowers on the left, male flower cluster on the right

The male, staminate flowers effectively resemble green balls on sticks, composed of five petals which open to reveal five pollen-producing stamens. They grow in long, loose bud clusters from internodes on the branch and once pollen is released the male plants will soon die off. Male flowers contain low levels of cannabinoids and terpenes.

Female pistillate flowers are formed of tight clusters of bracts, the small, teardrop-shaped green petals that we growers refer to as calyxes. Each bract or calyx contains the ovary and the pistillate hair or stigma, which is what growers call the pistil and is the part of the flower that catches airborne pollen. Once pollen lands on the stigma, it is transported down the pollen tube to the ovary where fecundation takes place and the seed is formed, filling and swelling the bract as it grows. The thick, white pistil or hair will shrivel and turn a brown or red colour one it has served its purpose. The seeds are usually mature after a further 4-6 weeks time.

Both cannabis flowers and leaves develop beautiful colours

After pollination, female plants will devote their energies towards seed production, at the expense of resin. This means that seeded buds will have lower levels of cannabinoids and terpenes, and is one of the main reasons we strive so hard to grow sinsemilla (seedless) flowers, quite apart from the awful taste of smoking a seed in a joint!

Trichomes

Trichomes clustered on a bud

Botanists are still unsure as to exactly why cannabis plants produce such a large quantity of trichomes, but most agree that they most likely have the function of protecting the flowers and developing seeds, whether from harsh UV light, insects, grazing animals or extremes of temperature.

Trichomes have two different basic types: Glandular and non-glandular, with the principal difference being that non-glandular trichomes grow without a trichome head or gland, having the appearance of small hairs and mainly developing on stems, leaves, petioles and to a lesser extent on the flowers themselves, while glandular trichomes are found mainly on the flowers and sugar leaves, and possess the resinous gland where the cannabinoids and terpenes are secreted.

Glandular trichomes under the microscope

Glandular trichomes are themselves divided into three main kinds, which are: bulbous, the smallest and least numerous; capitate-sessile, which are larger and grow low, close to the leaf surface; and finally capitate-stalked, which are the largest, most numerous trichomes, found in highest concentration on the flowers and those with the greatest cannabinoid content, appearing somewhat like a tall mushroom, with a long stem and a large, rounded head – the iconic image of a trichome.

As the flowers mature, the trichomes will change colour, starting out transparent, passing through a milky-white stage nearing maturity and going on to become amber coloured when fully mature. Different growers will harvest their flowers depending on personal taste and the effect they’re looking for, but on our blog you can read a useful guide to harvesting according to trichome ripeness, which will help you to bring your crop down at the optimum moment.

Hopefully after reading this you’re now a bit more familiar with the anatomy of the cannabis plant and will become a better grower as a result. Knowledge is power!

The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.