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.
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.
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.
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 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.
Cannabis Plants Anatomy: From Seeds To Buds
Many consumers have seen a cannabis flower and maybe leaf but have never seen a plant grow from seed.
When growing cannabis, it’s essential you become familiar with the anatomy of a cannabis plant to know what they need and prevent problems.
It’s crucial you know the parts of a cannabis plant such as roots, nodes, calyxes, and trichomes, and what they’re used for to be able to maintain a healthy garden.
1. Anatomy of female vs male plants
Cannabis plants are dioecious, this means they have separate sexes, so the plants can be male or female.
In cannabis, the female plant produces high levels of cannabinoids and develops flowers (buds) while the male plant produces low levels and develops pollen sacs.
When both of them interact, the pollen fertilizes flowers, producing seeds which are used for breeding and cannabis cultivation.
It’s essential you know which one you need to grow to achieve the desired results, so in this article, we’ll explain the main differences and the anatomy of a cannabis plant.
2. Seeds and seedlings
A seed is the first thing you need to start growing your own cannabis, a cannabis seed has a hard shell to protect the embryo, this embryo is what will develop into a seedling when germinated.
When exposed to the right temperature and moisture, you will see a seedling (baby plant) start to develop, this seedling comes out of the medium with a small pair of green rounded leaves named cotyledons.
The cotyledons already contain chlorophyll which allows the tiny leaves to perform photosynthesis but it’s only in the early vegetative stage that you will see the first pair of serrated leaves develop and this is when the plant will start to absorb energy and nutrients, and direct it to the growth of foliage and stems.
After 3-5 days of exposing the seed to germination conditions, you will see a white “tail” coming out of the seed, this “tail” will start to grow longer and thicker as soon as the seed is planted and will eventually become your plant’s taproot, which is the main root from where rootlets sprout.
Once the taproot grows to a considerable size, several lateral roots will start to emerge from it, forming a network of roots in the soil, this root network is responsible for absorbing water and nutrients which are vital for your plant’s growth.
4. Fan leaves
After the cotyledons have appeared, they will be exposed to sunlight. This is important because the cotyledons use photosynthesis to absorb sunlight and produce energy for the plant to grow. After a couple of days, the first serrated leaves will appear, and as the plant grows, bigger foliage will appear and each time they will have more apexes, which are the fingers of a cannabis fan leaf.
Depending on the genetics, the foliage can have five, seven, nine, or more fingers but either way, independent of the number of apexes, the fan leaves use sun, water, and C02 to produce sugars.
Also, the leaves are different depending on the genetics, for example, Indica leaves are usually wider with more fingers while Sativa leaves are thinners and have more fingers, there are also autoflowers that start with leaves similar to Ruderalis leaves and it can get complicated to differentiate so here’s a table to help you figure it out easier.
Cannabis leaf characteristics
|Sativa||Skinnier with up to 13 “fingers”.|
|Indica||Fat and wide leaves with up to 9 “fingers”.|
|Ruderalis||Short and compact, developing 3-5 “fingers.|
These sugars are a cannabis plant’s source of energy and it fuels growth and all the biological processes it needs.
Have in mind that even though the foliage is a part of a cannabis plant, they have low levels of cannabinoids so their purpose is to absorb sunlight, store water, and also protect the buds from sunburn but are not usually smoked.
5. Sugar leaves
Sugar leaves are regular leaves but unlike fan leaves, they’re not too big and usually grow in between the buds. This foliage can sometimes have trichomes on them but will depend on the trichome production of each specific strain.
These leaves contain less resin that buds and are usually not consumed but depending on the quality of the genetics, these leaves can be used to make edibles, oils, and extracts.
6. Pre-sex structures
The pre-sex structures appear on the internodes in the pre-flowering stage of the cannabis plant, if your plant turns out to be a male, you’ll see small balls appearing which are pollen sacs in the early stages.
These pollen sacs will eventually develop and open up, releasing the pollen needed to produce seeds, now, if you see white hairs (stigmas) instead of pollen sacs, your plant is definitely a female.
If you’re a home grower, you should “sex” your plants before they are completely mature, this will prevent the male plants from pollinating the female plants, have in mind that fertilized flowers will produce seeds which decreases the amount of cannabinoids and overall yield.
Now, if you’re a breeder or just want to experiment with cannabis breeding, you can have a breeding chamber so you can pollinate your plants in a controlled space and prevent cross-pollination because pollen is extremely light and can travel on your hair, clothes, and even by the wind.
7. Branches and stems
As said above, leaves absorb sunlight, and as new leaf growth appears, your plant will consequently get more light and the stem and branches will get thicker and thicker, developing more internodes (and more internodal spacing) on both sides of the stem.
The main part of a cannabis plant’s anatomy is the stem, the stem provides support to the foliage, branches, and flowers (basically the whole plant), inside the stem, there is a vascular system that consists of the Xylem and Phloem.
The Xylem transports water and the nutrients dissolved in water while the Phloem is responsible for transporting sugars, proteins, and other organic molecules in plants.
Sometimes plants can develop mutations, these mutations are genetic mutations so they cannot be fixed, and although some mutations can result in odd growth such as irregular branching and leaf growth, they can still produce good quality flowers, despite sometimes the yields being affected.
Nodes are the point where branches come off from the stem, in the vegetative stage of a cannabis plant they’re parallel to each other but when your plant begins flowering the appearance of nodes can become irregular, now this isn’t a problem at all, it’s just a characteristic of some cannabis strain and is usually a trait that can help you identify a certain plant’s species.
Have in mind that nowadays most cannabis strains are hybrids (a combination of Indica and Sativa genetics) so this won’t always be 100% correct but usually, Indicas tend to have nodes that are closer together while Sativa’s nodes are usually more spaced out.
These nodes are essential because they are where the buds or pollen sacs will start to develop and it’s where the first signs of your plant’s sex appear.
9. Flowers (buds)
The buds (flowers) are the most important part for growers but also for the cannabis plant, the flowers play several roles such as attracting pollinators and producing seed (once they’re fertilized) to perpetuate the species.
Nowadays you can find feminized seeds which means the seeds will result in 100% female plants but in nature, cannabis plants are dioecious which means the plants will be male or female, as said before.
The pre-flowering stage is vital in differentiating whether the plant is a male or a female because it’s when a plant will show the first signs of its sex.
The flowers that form on the top of the stem are known as the cola, typically, a plant has one main cola but growers have come up with several methods of creating multiple main colas with plant training techniques (such as LST and HST) that help increase yields.
The main cola is known as the apical bud or main cola and it’s where most of the buds gather together to form the main bud, you’ll also see small clusters of flowers between the foliage in the internodes but, compared to the main cola, the side colas are smaller so this is why growers use both LST and HST.
These two plant training methods end up changing the structure of the plant by exposing the flowering sites to more light and airflow, allowing the buds to grow bigger while also improving their quality.
When talking about flowers, there’s a distinction between female and male flowers. Male plants usually develop 2-3 weeks earlier than female flowers and, as said above, do not develop buds but they also form colas that consist of pollen sac clusters.
10. Pistils and stigmas
The pistils and stigmas are the reproductive parts of the female flowers, most cannabis consumers know the stigmas as pistils but that is wrong because the pistils are the part where the stigmas (white hairs) grow from.
These hair-like parts are responsible for collecting pollen grains from the male flowers and consequently, produce seeds.
When a cannabis plant is fully mature, the stigmas can change color several times, usually starting with white hues, then yellow, orange, or red, and lastly, brown.
Now, have in mind that the stigmas do not affect the potency or taste because they do not store any cannabinoids and don’t have trichomes so they won’t influence the quality and effect of your buds.
The bracts, which are usually called calyxes by mistake, are what actually form the buds on a cannabis plant, they are pear-shaped nodules that develop between the sugar leaves but depending on the strain, they can appear in several colors, shapes, and sizes.
When the stigmas get pollinated, the bracts essentially turn into an ovary (seed incubator) which allows the seeds to grow and ripen but ends up affecting the yields and can affect the resin quantity on your buds, that’s why “sinsemilla” or feminized seeds are preferred by growers and consumers.
A non-pollinated flower is usually trichome-rich because your harvest will have more trichomes and they are responsible for producing and storing terpenes and cannabinoids.
Trichomes are the tiny crystals found all over the buds and surrounding foliage and are considered the most important part for cannabis consumers, these mushroom-shaped glands are clear and sticky, and form a thick layer on the buds.
These mushroom-shaped glands known as trichomes can be found in different types and sizes, they are:
- Capitate-stalked trichomes 100 µm;
- Cystholitic trichomes 50 µm.
- Unicellular non-glandular trichomes 20 µm;
- Capitate sessile trichomes 20 µm;
- Complex bulbous trichomes 10 µm and;
- Simple bulbous trichomes 10 µm;
All “recreational strains” are THC-rich, depending on the strain, the trichome production may differ, resulting in more or fewer trichomes on your plants, but either way, all cannabis plants will produce trichomes.
For home growers, the trichomes are the standard practice to know exactly when to harvest but in nature, the compounds produce by the cannabis plant provide defense mechanisms, such as terpenes, which smell helps keep away predators.
Also, the sticky trichomes protect the buds from insects and against UV light, and although we don’t usually think about this when growing indoors, all the parts of a cannabis plant have an important role when cannabis plants grow in nature.
13. The Life Cycle of Cannabis Plants
Now that you know everything you need about the anatomy of cannabis plants, let’s understand a bit more about the life cycle of cannabis plants. Cannabis plants can take anywhere from 8 to 32 weeks to grow and mature, and during this time it goes through four stages, they are:
- Germination stage;
- Seedling stage;
- Vegetative stage;
- Flowering stage.
And it’s essential for you to understand these stages to grow healthy plants as each stage requires different light spectrums, light cycles, nutrients, and growing conditions.
The Germination Stage
Just like with any other plant, cannabis plants start from seeds. Cannabis seeds are dormant until exposed to warmth and moisture. This means that if you are looking to germinate cannabis seeds or any other type of seed, you will have to hydrate it and place it in good conditions.
After planted, seeds can take anywhere from 3 to 10 days to germinate and seeds contain enough food for 2-3 weeks, which means there’s no need to water with a nutrient solution until the seedling has come out of the soil. Once the seedling comes out of the soil, you’ll see two small rounded leaves which are called cotyledons, and this is what marks the beginning of the seedling stage.
The Seedling Stage
The seedling stage of cannabis plants can take anywhere from 1- 3 weeks, and sometimes more depending on the strain and growing conditions. During the seedling stage, plants focus on developing roots and foliage, this means that the roots are still small and fragile so be careful to not overfeed or overwater them. Once you’re in the seedling stage, make sure to provide 18 hours of light and 6 hours of darkness, and remember to keep an eye on them as they’re extremely susceptible to pests and diseases.
The Vegetative Stage
After a couple of weeks in the vegetative stage, your plants will start needing more food, light, and water as the roots and foliage start to grow exponentially. During the vegetative stage, you have to make sure you’re feeding your plant higher levels of nitrogen and less phosphorus and potassium as nitrogen is needed to develop foliage. If you’re growing indoors, the general rule is to flip to 12/12 (which triggers flowering) once the plant is ⅓ or ½ of the size you want them to be by harvest.
The Flowering Stage
Once you flip to 12/12 (or when autumn comes outdoors), your plants will start flowering. The flowering stage can take anywhere from 6 to 10 weeks or even more, depending on the strain. This stage starts with the appearance of pre-flowers which will eventually fatten up and turn into those delicious sticky flowers you’ve been waiting for so long. Obviously, this is just a quick rundown and there are a lot of things to keep in mind, other than the light cycle but understanding the life cycle and anatomy of cannabis plants will allow you to anticipate problems before they happen.
14. In conclusion
Cannabis plants are millennial plants that have developed and perfected their structure throughout the years, even though we don’t see it like that, all the parts of a cannabis plant are essential for them to grow and perpetuate their species.
Feel free to leave tips and more important information to help educate fellow growers, leave a comment in the comment section below!