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The Growth Cycle of Marijuana
Cannabis plant

Marijuana goes through many stages during its growth cycle.

Marijuana can grow from a tiny seed into a 10-15 foot tall plant, all within a short annual life cycle.

Growing cannabis from a seed into a mature plant involves a number of steps. Seeds need to be germinated, and the tender seedlings have to be nurtured as they grow from leafy juvenile to a flowering plant.

Once the plant has matured, it can be harvested and dried.

The Cannabis Plant

The Cannabis Plant
(Photo: Shutterstock)

Cannabis is a fast-growing annual plant. Sativas can grow up to 15 feet in height, while indicas can be as short as 3 feet. The plants are dioecious, which means they can be either male or female. Each sex produces different kinds of flowers.

The female plant produces the flowers we use for recreation and medicine, while the male plant produces a small, pollen-producing flower that doesn’t contain any THC. Growers tend to avoid male plants for this reason.

Cannabis is well suited for growing outdoors in a temperate climate. Commercial grows tend to be indoors — despite the cost of lights — because the plants can be protected from disease and are not limited by the short Northern growing season.

Maturation can take anywhere from 2-4 months, depending on growth conditions and strain.

Stage 1: Germination

Germination
(Photo: Shutterstock)

Cannabis seeds are very small, and are similar in size to flaxseeds. They are usually dark brown in color. Healthy seeds should feel dry and hard to the touch, with a shiny appearance. If the seeds are pale or feel spongy, they are not as likely to germinate.

Under good conditions, the seeds can germinate in 3-7 days. Cannabis thrives with lots of sunlight and well-drained soil. In the wild, cannabis tends to grow in ditches and riverside habitats, with warm, sandy soil or soils mixed with gravel for drainage.

At home, cannabis seeds can be germinated directly in the soil, or in wet paper towel or peat pellets. Peat pellets are moist and can be transferred to soil easily.

The first part of the plant to emerge from the seed is called the radicle, which is the very first root of the plant. As the root lengthens downwards, the new stem begins to grow upwards and pushes the seed out of the soil.

Once this has happened, the plant unfurls its first leaves, which are called cotyledons. These two leaves are small and round, and do not have the linear, toothed shape that marijuana leaves usually have.

These first leaves collect the sun’s energy until the plant can grow a little bit bigger and start unfurling its first true leaves. The germination process usually takes 1-2 weeks.

Stage 2: Seedling

Seedling
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Once the seed has grown its first pair of leaves, it can be considered a seedling. This growth stage is very delicate. The seedling stage lasts between 1-3 weeks.

The cotyledons collect energy from the sun, and soon the first true leaves of the plant can be seen.

Usually marijuana has compound leaves made up of 3-13 “fingers”, but the first leaves will have only one finger each. If you imagine the typical five-pointed marijuana leaf as a hand, each of the points would be one of the fingers.

This first set of fingered leaves grows up to 4 inches above the cotyledons, and will have the characteristic serrated edges. They grow in opposite pairs along the stem, one on each side.

As the plant gets taller, each new pair of leaves will have more fingers.

At this stage, the young seedling can grow rapidly. It needs moderate to high light intensity, moist but well-drained soil, and moderate humidity levels to thrive.

It is especially important at this stage not to overwater the seedling. Remember that it is tiny, and has a very small root system that can easily be drowned. The soil should feel moist, but not wet.

Stage 3: Vegetative Growth

egetative Growth
(Photo: Shutterstock)

The vegetative growth stage begins when the seedling has grown 7 sets of pointed leaves. It is more established and less fragile than it was as a seedling, and it can now enter its juvenile growth spurt.

During the vegetative stage, the plant produces many leaves, grows much taller, and develops its root system in preparation for flowering. Some strains can even grow up to 4 inches a day.

The lifecycle of cannabis is controlled by day length, and the vegetative stage corresponds to the long, warm days of summer. The vegetative stage lasts 4-8 weeks.

At this stage, cannabis needs lots of sun. If the plants are outdoors, the natural day-night cycle of summer will provide them with enough light.

If the plants are being grown indoors, they are typically kept on an 18 hour day cycle with a 6 hour night period. Cannabis plants can also be kept on a 24 hour light cycle, but this is costly and they usually do better with a cool down period.

During this stage, cannabis needs fertilizers high in nitrogen (N) and potassium (K).

Much like the seedlings, cannabis plants in the vegetative stage should be kept in well-drained soil, and watered often. It’s important not to drown the plant with too much water, and to allow the plant to dry out between waterings.

Interestingly enough, because light cycles control the shift from the vegetative to the flowering phase, plants can be artificially kept in the vegetative phase indefinitely.
Commercial growers do this so that they can raise new cannabis plants from cuttings, rather than germinating seeds.

Stage 4: Flowering

Flowering
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Once cannabis has finished its juvenile growth spurt, the flowering stage begins. This is the stage where cannabis starts producing its THC-rich flowers.

Unpollinated female flowers are called sinsemilla. They contain no seeds, and they produce more cannabinoids if left unpollinated.

The female flowers can be found at the base of the leaves, where they join the stem. This is called a node. At the node, there are two tiny, sharply pointed leaves that look like the tip of a blade of grass. Flowers will grow just above these stipules, one cluster on each side of the leaf.

The flowers are covered in trichomes, which are small glandular hairs. These trichomes produce THC, terpenes, and other cannabinoids. As the flower clusters mature, they produce more of these compounds and become sticky with resins.

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In order for marijuana to enter the flowering stage, it needs to have periods of 10-12 hours of uninterrupted darkness, signalling the end of summer.

This can be done artificially with growing lights, or can happen naturally outdoors when summer turns to autumn. Flowering cannabis plants prefer warm weather, and medium humidity. Much like in the vegetative stage, they need lots of water so they don’t dry out.

Indoor and outdoor cannabis will benefit from occasional fertilizing, to replenish the soil nutrients used up as they grow. The flowering stage usually lasts 6-8 weeks.

Harvesting

Harvesting
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When the flowering stage is complete and the flowers have fully matured, it’s time for harvesting.

Trichomes continue to produce THC and other cannabinoids as the flower ages, eventually reaching a peak concentration before the THC begins to degrade.

Harvesting should happen when the trichomes have produced as many cannabinoids as possible.

The cannabis plant has a few visual cues for when it’s ready to harvest.

As THC builds up in the trichomes, they turn a cloudy white color. Ideally, harvesting should happen when the majority of the trichomes are cloudy white, and about 10% of them appear a brownish, amber color.

Trichomes turn from cloudy white to brown when the THC begins to degrade. Having some trichomes turn this color is okay, and is an indication that the plant is ready for harvest. Immature trichomes appear clear, because they have a low concentration of cannabinoids.

Once the grower has determined the cannabis is ready, the process of harvesting it can begin. Since cannabis dies after flowering, the whole plant can be cut down or the branches cut off. Leaves have very low concentrations of THC, so they can be discarded.

Drying and Curing

Drying and Curing
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Once the leaves have been clipped off, the stems with the flower clusters attached can be hung to dry. Commercial cannabis is usually dried by controlling the humidity of the environment to 45-55%.

Drying is important to prevent bacteria or fungus from growing. It essentially preserves and lengthens the life of marijuana by removing the moisture content.

After drying, the flower clusters are removed from the stem and cured for 30 days or more.

The curing process involves taking the dried marijuana and aging it in a sealed, airtight container placed in a dark place. It is thought to make the marijuana more pleasant to smoke, improving the flavour, burn quality, and decreasing the harshness.

Some growers do not feel the need for curing, so this stage is optional.

Once marijuana has been dried and cured, it can be used for smoking, vaporizing, or making edibles.

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