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The Cannabis Life Cycle

Learn about the basic life cycle of cannabis plants from germination to harvest.

Cannabis is an annual plant. This means that cannabis goes through its entire life cycle within a year. Most strains of cannabis complete their life cycle, from seed to harvest, in 4-10 months. Cannabis is one of the few annuals that tend to have separate male and female plants. However, it is not unheard of for a cannabis plant to turn into a hermaphrodite (a plant with both male and female organs) in times of stress. This is especially the case in the wild, where cannabis strains do not have human intervention or care.


The process by which a plant grows from a seed. The most common example of germination is the sprouting of a seedling from a seed. This is the very beginning. All that is required to start germination is water, air and heat; the seed will use these to produce food and start its rapid growth. As the seed germinates the first shoot will grow and break out of the shell, this is the tap root. After this the plant will begin to grow, forcing its way upwards. It produces its first two leaves (known as the cotyledons), which should force the seed shell off the plant and open the way for them to catch light. This is the primary task of a newly germinated seed, to obtain as much light energy for food as possible through its new leaves. There are many different techniques to germinate seeds (some just put seeds directly in soil, some in a glass with water). The following was made by Simon, breeder at Serious Seeds, and details an extremely specific germination and seedling process.

Serious Seeds Germination Process

1. Take a piece of kitchen paper towel

2. Make the paper wet. Tap water is okay, but if you want to kill all the fungus and bacteria on the seeds you can wet the paper with a mix of 1 part 3% peroxide with 5 parts distilled water.

Tap water is usually fine.

3. let excess water drip off

4. Divide the seeds over half the paper towel and fold the paper towel in half. You should be able to do one pack of seeds per paper towel.

We do one variety per paper towel.

5. Put the paper towel inside a labelled Ziplock bag to keep it wet.

We recommend labelling the sandwich bags with each variety. You could also add the germination date.

6. Hang the paper towel up vertically; water will collect at the bottom of the baggie. Make sure to lift the bag horizontally every 2 days to keep the paper towel wet.

Hanging on the fridge is fine.

7. Check the seeds every day. When they have developed a taproot of about .5-1 inch you can move them into your growing medium.

8. Because we hung the seeds vertically in step 6, the roots grow straight downwards regardless of the position of the seeds on the paper towel.

9. You can carefully move the seeds from the paper towel to a growing medium by placing it carefully onto a spoon with your finger.

This little tap root came in about a day.

10. Before planting the seed, be sure to prepare your pot by wetting loosely pressed soil in the pot.

11. Make a hole in the soil, much bigger than the seed. Place the seed on the edge of the hole with the root pointing straight down. Be sure the root is straight down, and the seed is positioned on the edge (do not bury the seed).

12. Gently fill the hole with soil.

13. After filling the hole with soil the seed should be positioned half in the soil and half on top of the soil.

Can you find the seed?

14. Press the soil down around the seed so that the seed is on top of a ‘mountain’.

15. Make a deep circle around the mountain.

16. When you water your seeds, be sure to water in the circle you made. This way the seed does not get wet, but the roots take up water via the soil.

17. Place a plastic bag over the pot to keep warmth and moisture locked inside for the first few days.

18. Not enough light might make the seedling stretch. If the seedling gets long and thin be sure to support, it with a stick so it does not break.

19. The first leaves of the seedling (cotyledon) are not true leaves but contain food for the young plant for the first days, like a battery charging it up. The next pair of leaves that appear are true leaves which are single. Remove the plastic bag after the first true leaves are grown out.

These are the cotylydon
These are the first indication of serrated true leaves about a day later.

20. After the single leaf pair, the next leaf pair will have 3 leaflets each. The following leaf pair will have 5 leaflets, then 7 and then 9. Some plants will grow leaves with 11 leaflets. Generally, the healthier a plant, the more leaflets it has.

21. Bigger plants are less fragile and it’s safer to wait until they have a couple true leaves before placing them outside. Plants need to get used to the sun slowly, or they will burn. You can help the plant adjust to the strong rays of the sun by first putting them outside in the full shade for a day or two. Then place them under translucent plastic for another 2 days to filter the intense light. Once they are strong enough, they won’t burn and die when they are placed in direct sunlight.

Vegetative Period 

This is the main growing phase of the plant where it will turn from a small seedling into a large, beautiful cannabis plant. It is in this phase that the plant will require all the light and nutrients it can use – just be careful not to overfeed it nutrients, (a common rookie error). Indoors, the grower would use 18-24 hours of light to mimic summer daylight. If the plant has what it requires, it will start by continuing to grow upwards towards the light, producing new leaves while thickening its branches and stems.

When it begins to reach a certain level of maturity it will start to focus its efforts bulking outwards instead of upwards, creating more branches and nodes. At this point you can start looking for “pre-flowers”. These are tiny versions of adult sex parts, and when you see them, you can tell what gender the plant is going to be. They usually show up in the upper parts of the plant, closer to the light. Finally, when you see a calyx start to form around the nodes of the plant, you know you are in the final part of the vegetative period, and it is an indication that the plant is ready to flower. Alternatively, if it is a male plant, it will start to form tiny pods that will eventually produce pollen to pollinate another plant. Pollination occurs when pollen from the male cannabis plant reaches the female stigmas and finds its way to the egg cell of the female plant that is inside the pistil. After the process of pollination, the seed is produced. Hand pollination is when a breeder takes the pollen from the male plant with a brush and dusts it on the female plant. Outdoors’s pollination would occur naturally with wind blowing pollen form one side of a grow space to another.

On the left, developed male pods filled with pollen. On the right, female plants with preflowers forming.

Flowering Period

The flowering period starts towards the end of summer, when the plant gets less light as the days get shorter (indoors, the light cycle is reduced to 12 hours light, 12 hours dark). This is an indication to the plant that its life cycle is nearly up, and it needs to think about reproduction. It is around this time that the males will start to produce pollen and the females produce flowers (buds). Should the females’ flowers encounter the male pollen then they will begin to produce seeds within their buds. Once seeds are made the buds will open to allow for the seeds to disperse by natural means and start the entire cycle all over again. Cannabis cultivators tend to worry about their females getting pollinated because seedy pot is not good for smoking. The best way to overcome this is to move males to a separate place as soon as they are identifiable. This is to stop any risk of contamination. It is always best to produce seeds in a separate area, away from the main crop.


The harvest is not a natural part of the cannabis life cycle per se, but for the grower this is the most crucial and anticipated part of the grow. It is particularly important to get the timing exactly right here. Growers must be incredibly careful not to cut down plants that are not yet at the pinnacle of resin production, but they must also be wary of cutting plants too late- at a time when THC production has curtailed, and trichome resin glands begin to degrade. There are various methods by which even the most amateur grower can tell when buds are truly ripe for the picking. The simplest and quickest way to know is by examining the pistils, or long hairs, which cover the plant’s buds. At the onset of flowering, these pistils are white and stringy. Although as the flowering period ends, they begin to turn colour, first from white to orange and then again to a dark red, pink or brown.

White pistils early in flowering vs. orange pistils at the end of flowering.

These colour changes signify the maturation of the buds; however, the colour and time frame may vary significantly across different varieties of cannabis. The best method for determining ripeness is through trichome examination. Trichomes are the actual resin glands that contain THC and other cannabinoids, and they are very delicate and easily ruptured. These trichomes are visible on the outside of buds and small leaves and look like little white sugar crystals to the naked eye. However, with the power of a magnifying glass or simple microscope, you can see that trichomes are comprised of a stalk and resin head (that look like a penis) and are clear or white in colour. As with pistils, trichomes also begin to change colour as the buds mature. Although in this scenario, a grower wants to harvest buds before they get too dark in colour. Even a subtle amber hue in these glands could mean that cannabinoids have begun breaking down and decomposing, which means less potent pot. Advanced growers use a 45x – 100x microscope and look for a creamy or milky white colour in the trichomes that tells them it’s time to harvest.

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