Cannabis plant growth is a fascinating subject. We’ve made a handy guide to the stages of growth, from seedling to harvest!
Germination of Seeds
The first stage in cannabis plant growth is the germination of the seeds. This occurs when the seed has sufficient water, oxygen, and warmth. It’s not even necessary to provide soil at this stage – in fact, many growers germinate their seeds by placing them into a cup of water for 24-72 hours! Many others use cotton wool or a piece of kitchen paper to germinate. Just make sure your seeds remain moist at all times, whatever method you use.
It’s important to prevent your seeds from getting too cold or too hot – the best temperature range is 23-26 C (75-80 F). Many cannabis seeds will germinate at as low as 10 C (50 F) or as high as 40 C (104 F), but extremes will slow their growth.
When your seed germinates, water swells and softens the hard outer coat, causing it to break. As water and oxygen pass through, they kick off cellular processes that were dormant while the seed was stored. Cells begin to divide and multiply, and growth begins.
Embryonic Root Growth
The first part of the plant to form is the embryonic root. This is also known as the radicle, or primary root. After the primary root establishes itself, secondary (“seminal”) roots start to split off from the radicle, followed by small, web-like lateral roots. Later, “adventitious” roots may emerge from parts of the stem, and not directly from the radicle.
To create the radicle, the plant uses the food reserves within the seeds. Once the root emerges from the seed, it’s ready to start absorbing nutrients from the soil. So once the root emerges, place your seedling into a small container so that it can absorb nutrients and continue on to the next stage of growth.
Embryonic Shoot & Cotyledons
The next stage of cannabis plant growth is the appearance of the embryonic shoot and the cotyledons, the first tiny leaves. Anyone that’s germinated cannabis seeds will recognize the two tiny, rounded leaves that first appear. They’re very different from the leaves that will grow later! During this stage, your plants are very tiny and very vulnerable – but they will get through it quickly and be on to the next stage in just a few days.
Once the first “true” leaves appear, the plant has begun vegetative growth. The first true leaves are serrated – but at first, each leaf only has one leaflet. The first set of two leaves are followed by leaves with increasing numbers of leaflets until reaching a maximum number (usually between 7 and 13). At first, the sets of leaves grow in an “opposite” orientation, but later leaves will appear one by one on alternating sides of the stem.
After a few sets of leaves appear on the main stem, you will see tiny new shoots in the corners of the petioles (the stalks that join the leaves to the stem). These new shoots are the first branches, and over the next few weeks, these branches will grow, divide, and strengthen. Now is the time to practice pruning techniques, to create more and stronger eventual flower sites.
Appearance of Preflowers
Before cannabis begins to flower in earnest, it will put out tiny “pre-flowers” at the junctions of the main stem, which will allow you to ascertain if your plants are male or female. Female pre-flowers appear somewhat like a tiny, green, furry cat’s ear with a delicate strand of whitish or pinkish hair poking out of it. Male pre-flowers appear like a tiny ball on a stalk and don’t have that characteristic hair.
If growing outdoors in natural light, many strains of cannabis begin to flower when the cycle gets close to 12/12. That’s the period of the autumn equinox – around September 21st in the Northern Hemisphere and March 21st in the Southern.
If growing indoors, you’ll usually need to switch your plant’s light cycle to 12/12 to see pre-flowers emerge. But many strains will also show pre-flowers if they are kept in vegetative conditions for long enough, even if you didn’t switch the light cycle yet.
The Flowering Period
After the pre-flowers emerge, you’ll see more tiny little flower sites at the tips of the stems, and the junctions between leaf, branch, and stem. These tiny flowers just keep on appearing for several weeks, growing steadily bigger as they do.
In natural conditions of cannabis plant growth, the male pollen would now fertilize the female flowers, causing the formation of seeds. However, in most grows you’ll be separating any males from the females, as seed growth is usually undesirable. When we deprive the female flowers of male pollen, they put a lot of that excess energy into producing resin instead.
During the early part of flowering, the branches of your plants will continue to grow. In some varieties, plants can stretch a huge amount during this time. So make sure you don’t let them get too big during vegetative growth.
Harvest Time & Plant Death
When your plants are ready, they will show you that it’s time to harvest in various ways. The leaves will begin to turn yellow and die, and the flowers themselves will change. The tiny hairs that cover the buds will turn from white to brown or red, and the trichomes (the “crystals”) will turn from transparent to milky. If you leave the buds a few days more, the trichomes will start to turn amber. A few amber trichomes may not be a bad thing, but it indicates that THC is turning to CBN, so too many is probably undesirable.
At this stage, the cycle of cannabis plant growth is complete. If male pollen was present, seeds would now be ripe, and as the plant dies, they would fall from the flowers to the ground below. Those seeds would remain dormant over winter before germinating in the spring, starting the whole cycle off again!