Cannabis Life Cycle and Indoor Growing
Introduction
Cannabis cultivated indoors needs light (1), air (2), a growing medium (3), warmth (4), nutrients (5), and water (6). As explained earlier in this chapter, you can control all these needs in your indoor garden and achieve optimum results.
Cannabis is a short-day plant. In nature, it flowers when autumn days are short and nights are long. Outdoors, cannabis normally grows as an annual plant, completing its life cycle within one year. A seed that is planted in the spring will grow through the summer and flower in the fall, producing more seeds.
Cannabis goes through three distinct stages of growth: seedling, vegetative, and flowering. Most varieties or strains will stay in the vegetative growth stage as long as they receive 18–24 hours of light and 6–0 hours of darkness. Most strains of cannabis will flower when they receive 12 hours of light and 12 hours of uninterrupted darkness.
Indoors you can use this knowledge to control the life cycle and harvest up to six crops a year.
Seedling Growth
Seed germination is induced with moisture, heat, and air which activate hormones within the seed. Within 24– 72 hours the seed’s coating splits and a white rootlet emerges and continues to grow. The Nebula seeds (right) have been germinating for 24 hours.
After three to seven days of germination, the rootlet grows downward and a sprout with seed leaves pushes upwards in search of light. Plants like the Jamaican Pearls (right) continue the seedling growth stage about a month. During this stage the seed establishes a root system and grows a stem and a few leaves. Seedlings need 16–18 hours of light to grow strong and healthy.
Vegetative Growth
Vegetative growth is maintained in this AK-47 and other strains by giving plants 18–24 hours of light every day. As the plant matures, the roots take on specialized functions of transporting and storing food. The root tips push farther and farther into the soil in search of more water and food. The delicate root hairs actually absorb water and nutrients. Delicate root hairs will dry up and die without water. They are very frail and are easily damaged by light, air, and bumbling hands if moved or exposed.
The stem also grows upward producing new buds along the stem. The central or terminal bud of this Thaitanic carries growth upward; side or lateral buds turn into branches or leaves. The stem carries water and nutrients from the roots to the growing buds, leaves, and flowers. If the stem is bound too tightly by string or other tie-downs, it will cut the flow of life-giving fluids, thereby strangling the plant. The stem also supports the plant.
Often indoor plants develop weak stems and may need to be staked up, especially during flowering. Bending and training plants also makes best use of light indoors.
Chlorophyll (the substance that gives plants their green color) converts carbon dioxide (CO2) from air, water, and light energy into carbohydrates and oxygen. This process is called photosynthesis. Tiny breathing pores called stomata are located on the underside of the leaf and funnel CO2 into contact with the water. The stomata open and close to regulate the flow of moisture, preventing dehydration. The stomata also permit the outflow of water vapor and waste oxygen.
Pre-flowering
Cannabis grown from seed grows pre-flowers after the fourth week of vegetative growth. You can see a male pre-flower nub in the photo above. They generally appear between the fourth and sixth node from the bottom of the plant. Canna- bis plants are normally either all male or all female. However, occasionally an intersex plant with both male and female flowers will appear. Each sex has its own distinct flowers. Pre-flowers will be either male or female. Growers remove and destroy the males (or use them for breeding stock) because they have low levels of cannabinoids (chemical components of marijuana: THC, CBD, CBN, etc.). The most desirable female plants are cultivated for their high THC content.
Flowering
Flowering is triggered in most strains of cannabis like the Chronic bud (below) by 12 hours of darkness and 12 hours of light every 24 hours. Once flowering is induced with the 12/12 light/ dark schedule, they are at peak ripeness in 7–12 weeks. Plants that developed in tropical regions often start flowering under more light and less darkness.
Flowering Male Plants
Male seedlings that were not removed during pre-flowering are removed as soon as male flowers are visible so that they do not pollinate females. A grower removed the Super Silver Haze plant (left) from his garden as soon as he saw the male flowers.
Flowering Female “Sinsemilla” Plants
Unpollinated female flower buds develop without seeds, known as “sinsemilla.” Sinsemilla flower buds continue to swell and produce more resin while waiting for male pollen to successfully complete their life cycle. After weeks of heavy flower and cannabinoid-laden resin production, THC production peaks out and buds are ready to harvest.
Seed Crops
When both male and female flowers are in bloom, pollen from the male flower lands on the female flower, thus fertilizing it. The male dies after producing and shedding all his pollen. Seeds form and grow within the female flowers such as the seeds of the Sweet Diesel (left). You can collect the seeds roughly six to eight days after pollination.
Mother Plants
Select strong, healthy, potent mother plants. Give mothers 18–24 hours of light daily so they stay in the vegetative growth stage. Cut branch tips from mother plants and root them. The rooted cuttings are called “clones.” Cultivating several strong, healthy mother plants is the key to having a consistent supply of all-female clones.
Clones
Cut branch tips and root them to form clones. Clones take 10–20 days to grow a strong healthy root system. Give clones 18–24 hours of light so they stay in the vegetative growth stage. Once the root system is established, transplant clones into larger containers. Now they are ready to grow for one to four weeks in the vegetative growth stage before being induced to flower.