There are several stages of cannabis growth you should familiarize yourself with if you are going to grow weed. A cannabis plant starts out as a seed, becomes a seedling, grows vegetation and then flowers. During flowering, if it gets fertilized the plant will produce seeds. Unless you are trying to grow for seeds like those who are cannabis breeders, you will want to keep all male pollen away from your plants.
Seed and Germinating
Moisture heat and air all act on a seed to release hormones that induce germination. Germination is also known as sprouting, or seed sprouting. This process takes 3-4 days for most seeds depending on how old the hormones are inside the seed. Whether or not the hormones are activated properly is sort of uncontrollable. For more on how to actually germinate your seeds go here.
Seedling Stage of Cannabis
A cannabis plant is considered to be a seedling from the time it sprouts to about 4 weeks after. During this time it will establish its main roots and begin growing its first leaves. The roots will serve to anchor the plant in the grow medium as well as draw in chemicals needed for life.
Vegetative Stage of Growth
The vegetative stage of growth occurs after the seedling stage and is when the plant will strengthen its stalk and grow its leaves and branches. This is when the water and nutrient delivery system is established within the cannabis plant. Water and nutrients are absorbed from the soil and transported through the stalk and into the vegetation.
The duration of the vegetation phase will greatly depend on the strain you are growing. The vegetation phase is also referred to as simply the vegging stage. During the vegging stage you will need to give plants 18-24 hours of light.
Flowering Stage of Cannabis
The flowering or budding stage of cannabis is the final stage of cannabis growth. This is when the usable part of the marijuana plant finally begins to grow. Flowering stages last for as little as 6 weeks or as long as 13 weeks. Knowing when to harvest is dependent on your ability to notice mature trichomes on cannabis flowers. The job of the cannabis flower is to create and dispense seeds for the next generation. If no pollen from males is around then no seeds will form but be aware, an all female crop can spring up some hermaphrodites and carry pollen to the other plants.