Cannabis is considered a short-day plant that flowers in the fall. It regulates its growth and flowering stages by measuring the hours of uninterrupted darkness to determine when to flower.
Flowering Week by Week
Within three or four days of initiation to a daily dark period of 10-11 hours, cannabis changes its growth pattern from vegetative to flowering. After that it is on a course that ends with bud ripening. Most modern plants take 7-9 weeks, although some sativa strains take longer.
Week 1: The plant slows down its growth
Week 2: The first flowers appear at the nodes
Week 3: Vegetative growth continues as the plant grows a total of between 25-50% larger than when flowering started.
Week 4: Vegetative growth has ended and the plants concentrate more of their energy into flowering. Odor becomes more noticeable as the plants start to produce capitate trichomes.
Week 5: Flower growth proliferates quickly. The flowers become thicker in areas where they have previously grown and they appear in new places along the top of the branch. The odor increases as more trichomes are noticeable and the odor intensifies a little.
Week 6: Flower growth continues in varieties that take longer to mature. It slows and then stops in seven-week varieties as the plants begin to ripen. The calyx behind the stigmas begins to swell. The odors of the seven-week varieties intensify.
Week 7: The calyxes in the seven-week varieties swell to near bursting as THC is produced in the glands. At the end of the week they will be ready. The trichomes stand more erect and the caps swell with newly produced resin. At the end of the week the flowers reach the peak zone. The odor is intense and the glands, filled with resin, fluoresce. Growth stops in the eight-week varieties as the flowers start to mature.
Week 8: The flowers are ripe by the end of the week, and reach the peak zone in the last 72 hours. After that, they will start to deteriorate if they aren’t harvested.
The cannabis plant is comprised of several structures, many of which we can find on any ordinary flowering species. Cannabis grows on long skinny stems with its large, iconic fan leaves extending out from areas called nodes. Cannabis really starts to stand out in her flowers where unique and intricate formations occur.
Also known as the terminal bud, cola refers to the plant’s “bud site” where tight female flowers bloom. The main cola (sometimes called the apical bud) forms at the very top of the plant, while smaller colas occur along the budding sites below. The number and size of cannabis colas can be increased through a variety of growing techniques like topping, low stress training (LST), and screen of green (ScrOG).
To the unknowing eye, cannabis buds just look like a knobby tangle of leaves, but the calyx is what actually comprises the female flower. Look closely underneath those tiny leaves (called “sugar leaves”) and you’ll find those tear-shaped nodules. These are the calyxes, and they come in many different shapes, sizes, and colors. Calyxes typically contain high concentrations of trichomes, or glands that secrete THC and other cannabinoids.
Out from the calyxes peek tiny red-orange hairs; these vibrant strands are called pistils, and they serve to collect pollen from males. Pistils begin with a white coloration and progressively darken to yellow, orange, red, and brown over the course of the plant’s maturation. They play an important role in reproduction, but pistils bring very little to the flower’s potency and taste.
Despite their minute size, it’s hard to miss the blanket of crystal resin on a cannabis bud. This resin (or “kief” when dry) is secreted through translucent, mushroom-shaped glands on the leaves, stems, and calyxes. Trichomes were originally developed to protect the plant against predators and the elements. These clear bulbous globes ooze aromatic oils called terpenes as well as therapeutic cannabinoids like THC and CBD. The basis of hash production depends on these trichomes and their potent sugar-like resin.