Indoor Cannabis Life CycleOverview

Soft Secrets
14 Nov 2014

Growing Cannabis indoors allows the gardener to control – and create – the seasons and environment.

Growing Cannabis indoors allows the gardener to control – and create – the seasons and environment.

The natural life cycle of Cannabis plants can be somewhat manipulated to the advantage of the savvy indoor gardener.

The radicle or tap root has burst through the seed coat

Successfully Germinating Cannabis Seeds

All uniquely genotyped - that is, non-cloned - Cannabis plants start as a seed. A seed contains a tiny live plant or embryo in stasis, with a food store (endosperm) inside a protective shell known as a seed coat. The tiny plant already has two seed leaves, called cotyledons - because Cannabis is a dicotyledon, also known as a dicot - plus a stem (hypocotyl) and a root (radicle).

Under the right conditions, viable (live) Cannabis seeds will sprout. The seeds require moisture and warmth, although until they sprout they do not need light. To conserve space and help keep the sprouting seeds manageable, moist paper towels, rooting cubes, celled partitions in 1020 trays and plastic cups are just a few of the options that can be used as seed-starting containers - a soldering iron can make neat, round holes in plastic cups or other PET beverage containers. Make sure to note the planting date, as well as the varieties planted; plastic label stakes (or plastic spoons with labels) can be moved from container to container with the plant.

A warm location is preferred; sometimes, a seedling heating mat is used to help maintain sprouting temperature.

Moisture passes through the seed coat through tiny holes called micropyles. Although not usually necessary, pre-soaking the seeds in water may hasten this process. The moisture swells the embryo, which employs hydraulic pressure to burst the seed coat. The radicle extends to establish the root system and the cotyledons unfurl to become the first leaves of the plant.

Seedlings are tender and susceptible to mortal damage. As such, they should be treated with a light hand and great care.

Vigorous growth occurs during preadolescence: the plant develops in size, both in leaf and shoot development, and extends the root system. As they outgrow their original containers, they should be carefully transplanted into larger containers.

An immature sprout is grown with short dark periods to prevent premature flowering

The Advantages of Cloning Marijuana

Cuttings are sometimes taken from a plant and rooted in a process known as vegetative propagation (also known as cloning). A growth tip and a section of stem are cut from the parent plant; the stem is kept moist and placed in a lighted, warm location until roots develop. This is possible because the stem contains undifferentiated cells - those that have not yet declared what type of cell they will become - known as meristem cells which, under the right conditions, will become root cells.

Plants started from cuttings are basically sections of the same plant in multiple places, thus they tend to be very similar to each other. These types of plants are commonly referred to as clones, since they share the same DNA.

Gardeners use this to their advantage to increase numbers of superior specimens, or to learn about a particular plant by examining its cutting. For example, if a plant clone is cut and rooted and then exposed to flowering conditions, the gender of the parent plant can be determined, even though the original parent plant has not yet started to flower (if the cutting of a plant produces female flowers, then the original or mother plant will also have female flowers, etc). Making sure that each cutting has an appropriate label can simplify identification and ease the matching plant cutting to parent.

Cannabis is photo-dependent for flowering, as it uses photoreceptors known as phytochromes to track the length of the dark periods. It is known as a short day plant because when exposed to long nighttime or dark hours, it will flower (an exception to this is the auto-flowering varieties, which will flower regardless of the length of the dark periods). Indoor growers use this knowledge to their advantage. For example, the dark periods can be kept short, or eliminated altogether, in order to keep the plant in an immature phase to encourage vigorous growth. This is why dark periods tend to be six hours or fewer in vegetative growth.

When the gardener decides to initiate flowering, they extend the dark periods to simulate the longer nights of fall (eleven to twelve hours).

This small, seeded bud has over-matured and is nearing the end of the life cycle

Preventing Seed Formation in Marijuana Plants

Once flowering conditions are met, the plant will enter adolescence and begin to produce flower buds. As energy from the plant is diverted from growing larger in favor of flower development, overall growth slows. Cannabis is part of a group of plants that have individuals that either produce only male flowers or only female flowers (dioecious). Male flowers appear as clusters of 'balls' (pollen sacs with stamen), female flowers have sets of whitish 'hairs' (pistils) protruding, both of which represent the sexual organs of Cannabis plants.

As the flowers reach maturity, they open and become available for reproduction. If pollen from a male flower organ reaches a receptive female flower organ, then seed development can occur. Removal of male plants as they are identified is a common tactic to prevent pollination and seed production. The primary way to prevent dioecious plants such as Cannabis from producing seeds is to remove any male plants (and their pollen) so that the female flowers do not become fertilized. This is the generally preferred method of growing Cannabis for consumption, as non-pollinated buds will not produce seeds and will result in stronger, better-quality smoke.

When To Harvest Cannabis

The exact time of harvest is a matter of some debate between growers. Some prefer to harvest early and other later. However, in general, the buds will have swelled, at least some of the hairs have started to discolor and the resin glands are, at least for the most part, no longer clear.

In nature, Cannabis is considered to be an annual plant as it drops seeds for the next year at the end of the life cycle, completing the cycle in a single year. In a production or commercial indoor garden there is no pollen from which to make seeds and plants are harvested well before they would die naturally.

Understanding the basic life cycle of plants can be helpful in knowing what to expect from your garden, and in what order.


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