Cannabis Plant Anatomy: A Guided Tour for Growers

If you are considering embarking on your first grow, it is essential to understand cannabis plant anatomy. This includes how to recognize the key structures of the plant and the individual roles they play in its development and health. Even if you are not a grower, it can still be useful to increase your knowledge of the subject to ensure you are using top-quality buds.

This article offers a whistle-stop guided tour of the anatomy of a cannabis plant. We will also discuss how to tell female plants apart from males and hermaphrodites, even before flowering occurs.

What Does a Marijuana Plant Look Like?

Cannabis sativa, also known as marijuana or weed, has a distinctive appearance and has been portrayed in the media so often that it is instantly recognizable to most. The plants usually consist of a straight stem with opposite or alternating branches and unmistakable fan-like leaves.

Female plants produce dense clusters of flowers that are known for containing the plant’s sought-after cannabinoids and terpenes. Meanwhile, male plants produce small pollen-filled sacs and are considered less useful unless you are a cannabis breeder.

Despite their well-known silhouette, marijuana plants can vary considerably in their size, color, and growing habits. They can range from 1-6 meters in height and exist in a spectrum of colors, with green and purple being among the most common.

Some varieties are short and bushy, while others are tall and tree-like, with sparser foliage and smaller buds. The former structure is typically associated with indica strains, while the latter is more common among sativas and industrial hemp.

Although one plant can differ significantly from another, all of them have common features that are essential to their survival. We will discuss the most crucial of these structures in detail below.

Marijuana Plant Anatomy

A basic understanding of cannabis plant anatomy is essential for growers, as it will help them identify potential problems with their plants, apply training techniques for higher yields, and distinguish female plants from males.

Here are some of the key structures, how to recognize them, and their role in the plant’s development and overall health.

Seeds

Cannabis seeds carry DNA from one generation to the next and are essential for the continuation of a genetic line.

Many growers start their projects using seeds, and there are various options available. Feminized seeds are the best choice, as they reduce the risk of finding unwanted male plants in your garden. Autoflowering seeds are another popular option, as they bloom quickly and do not require changes in the light cycle to trigger flowering.

Cannabis seeds tend to be oval in shape, with a smooth brown or mottled shell. This shell contains the seed itself and will split once the seed germinates to produce the plant’s first tap root. To learn more, check out our article on germinating cannabis seeds.

Roots

Cannabis plants have one main tap root surrounded by a complex network of lateral roots. These roots draw water and nutrients from the growing medium and anchor the plants down to prevent them from falling over or blowing away.

Weed roots are deep and can reach up to 2.5 meters when growing outdoors in loose soil. A more typical depth when growing indoors is 30-60cm.

Cannabis roots are susceptible to issues such as root rot, so avoid overwatering your plants to prevent this potentially fatal pitfall. Our in-depth guide explains how to water cannabis plants properly.

Stems

In nature, a cannabis plant stem is long and straight, providing a central point for the lateral branches to grow out from. However, certain training techniques can result in one stem that grows horizontally or multiple stems on the same plant.

The main stem tends to be strong, woody, cylindrical, and with vertical ridges. It gives the plant structure and is essential in transporting water and nutrients from the roots to the leaves and flowers via the branches.

Branches

Weed branches attach to the main stem in either an opposite or alternating pattern. At one end, they have a structure called a node, and at the other end, they have a fan leaf (see below).

Their function is to transport nutrients and water from the plant’s stem to the leaves, and they are removed in certain training techniques in order to direct more of these valuable resources to the bud sites.

Node

Cannabis nodes are the areas where a branch emerges from the main stem. They are crucial when trying to determine the sex of your plant, as female or male preflowers form here long before the main bud sites.

Therefore, it is essential to keep checking your plant’s nodes throughout the vegetative stage, especially if you did not use feminized seeds. Keep reading to learn how to tell the difference between female and male cannabis plants.

Fan Leaves

Fan leaves are the fan-like leaves that are so often used to represent cannabis in popular culture. They consist of 3-9 lobes, or leaflets, with the most common number being 7. Each lobe is 6-11cm long and 2-15mm wide, with pointed tips and serrated edges.

The distinctive shape of weed leaves makes the plant easy to recognize, even from afar. In scientific terms, this leaf shape is known as “palmate,” and it may provide evolutionary benefits, such as more efficient distribution of nutrients.

The main function of fan leaves is to generate energy for the plant via photosynthesis, which converts carbon dioxide and water into glucose and oxygen in the presence of light. Plants also use their leaves to “breathe,” a process known as transpiration.

Although fan leaves are a crucial part of cannabis anatomy, many growers choose to remove a significant proportion of them throughout the plant’s life cycle. This is because having too many fan leaves can block light from the lower parts of the plant and reduce bud production. Removing fan leaves also helps the plant focus its energy on producing large and potent flowers.

However, it is essential to avoid removing too many at once as that will leave the plant low on resources and potentially send it into shock or, worse still, kill it off completely. Furthermore, fan leaves can provide crucial clues to nutrient deficiencies, as they may turn different colors in the absence of specific minerals.

Sugar Leaves

Sugar leaves are resin-coated leaves that grow around the flowers of cannabis plants. They are covered in tiny glands called trichomes (see below), which produce many of the plant’s beneficial compounds, such as cannabinoids and terpenes.

Sugar leaves are not as potent as cannabis flowers, but they do still contain significant levels of these compounds. Although many people choose to manicure their buds to remove sugar leaves after harvesting, the “trim” is still useful and should not be thrown away. It may be too harsh to smoke, but could be used to create hash or edibles.

Flowers

Female cannabis flowers are the real star of the show, as they are the part of the plant richest in cannabinoids and terpenes. They are not single flowers like a rose or daisy, but rather many tiny flowers growing tightly clustered together to form a structure called an inflorescence.

Each inflorescence comprises numerous individual flowers and several other structures, which are described in detail below. In nature, inflorescences house the plant’s reproductive organs and produce seeds when pollinated by a male plant.

Male cannabis flowers look very different from their female counterparts, and this is one key way of telling the plants apart. We explain these differences in the following sections.

Cola

The cola is a cannabis plant’s main bud site, located at the top of the central stem. This area has the easiest access to nutrients and the most exposure to light, helping it produce dense, trichome-laden flowers.

Many training techniques focus on preventing a central cola from forming to increase the number of prolific bud sites. This can be done by topping the plant early in its growth cycle to create several stems with smaller colas or encouraging the plant to grow horizontally, as in the screen of green technique.

Bract and Calyx

The bract and calyx are structures that surround and protect the plant’s flowers. The bract is a small structure that looks like two tiny leaves emerging from the node between a branch and the main stem or nestled among the sugar leaves. It is covered in trichomes and is a good source of cannabinoids and terpenes.

Meanwhile, the calyx is the structure that protects the reproductive organs. It is not as easily visible in cannabis as in other plants, and many people confuse the bracts for the calyx.

Stigma and Pistils

The stigma and pistil are the reproductive parts of female cannabis flowers. The term “pistil” describes the whole female reproductive system. Each pistil produces two stigmas, which can be seen as tiny “hairs” protruding from the buds.

The stigmas start off white and gradually change color as the plant matures. This is one key way to determine when your plants are ready for harvest. However, a more reliable method involves looking at the trichomes.

Trichomes

Trichomes are the crystal-like resin glands that cover a female plant’s sugar leaves and flowers. They are the powerhouses that produce cannabinoids like THC and CBD and the terpenes that give cannabis its distinct aromas and flavors.

There are several different types of trichomes, including bulbous, capitate sessile, and capitate stalked. These terms refer to the trichomes varying shapes. Capitate stalked trichomes are predominant on female flowers and look somewhat like a tiny mushroom (capitate means “with a head”).

You can view these trichomes with a magnifying glass to determine when to harvest your plants based on their coloring. They start off clear and turn milky white as the plant matures, signifying it is ready for harvest. However, if you leave the plants too long, the trichomes may start to turn yellow, meaning their cannabinoids are beginning to break down.

Male vs. Female Weed Plants

If you are growing cannabis, you will need to know how to tell the difference between male and female marijuana plants. We will not go into great detail on this subject here, as we have another in-depth article on how to tell female plants from males. However, in brief, you need to look at the plant’s flowers as well as its overall structure.

Male Cannabis Plant

A male marijuana plant tends to be taller and thinner than a female and is often paler in color. Its flowers are dangly, ball-like pollen sacs that emerge from the nodes and central stem.

If you notice these features on your plants, you will want to remove them from your garden as quickly as possible to prevent them from pollinating the females. If that happens, the females will produce seeds, which diverts their energy away from cannabinoid production and results in less potent weed.

If you plan on breeding cannabis, you could keep the male plants and collect their pollen for later use. Otherwise, you can use their leaves to make a healthy green smoothie or as a garnish on any other dish.

Female Cannabis Plant

A female marijuana plant tends to be shorter and sturdier than a male but take into account that some strains are naturally squatter than others. They have thicker stems designed to support their heavy buds and also tend to be darker in color.

Female cannabis flowers have a teardrop-like shape with two protruding white “hairs” (the stigmas). They emerge in pairs at the plant’s nodes and in larger clusters along the main stem.

Female cannabis plants are prized for their resin, which is rich in cannabinoids and terpenes. Using feminized seeds ensures that you are growing female plants rather than males.

How to Tell if Your Plant Is Male or Female Before Flowering

Male and female weed plants produce pre-flowers a few weeks into their growth cycle, well before they begin flowering in earnest. You can see these pre-flowers at the nodes between the branches and the main stem.

Male plants will have ball-like pollen sacs, while females will have two wispy white hairs emerging from a teardrop-shaped structure, with one located on either side of the branch.

Hermaphrodite Plants

In some cases, a female weed plant can start producing male flowers, resulting in a hermaphrodite cannabis plant. This is bad news, as the plant can pollinate itself and begin producing seeds.

Hermaphrodites usually develop as a result of plant stress, so keep an eye on your environmental conditions and be sure to keep your ladies happy as they grow. Pay attention to lighting, temperature, humidity, watering, and nutrients, and you will be well on your way to a successful harvest.

Final Thoughts on Cannabis Plant Anatomy

Most people can recognize weed plants, but few understand the various parts of their anatomy and their functions. However, this is vital information if you intend to grow your own or even if you are just a cannabis enthusiast wanting to learn more about your passion.

We hope this article has increased your knowledge and that you are now armed with the information you need to complete your first successful grow. Happy gardening!