Chapter 2 – Medical Grower’s Bible
Introduction
The seedling growth stage lasts for about two to three weeks after seeds have germinated. Once a strong root system is established and foliage growth increases rapidly, seedlings enter the vegetative growth stage. When chlorophyll production is full speed ahead, a vegetative plant will produce as much green, leafy foliage as it is genetically possible to manufacture as long as light, CO2, nutrients, and water are not limited. Properly maintained, marijuana will grow from one-half to two inches per day. A plant stunted now could take weeks to resume normal growth. A strong, unrestricted root system is essential to supply much needed water and nutrients. Unrestricted vegetative growth is the key to a healthy harvest. A plant’s nutrient and water intake changes during vegetative growth. Transpiration is carried on at a more rapid rate, requiring more water. High levels of nitrogen are needed; potassium, phosphorus, calcium, magnesium, sulfur, and trace elements are used at much faster rates. The larger a plant gets and the bigger the root system, the faster the soil will dry out. The key to strong vegetative growth and a heavy harvest is supplying roots and plants with the perfect environment.
Vegetative growth is maintained with 16 or more hours of light. I used to believe a point of diminishing returns was reached after 18 hours of light, but further research shows that vegetative plants grow faster under 24 hours of light. Marijuana will continue vegetative growth a year or longer (theoretically forever), as long as an 18-hour photoperiod is maintained.
Cannabis is photoperiodic-reactive; flowering can be controlled with the light and dark cycle. This allows indoor horticulturists to control vegetative and flowering growth. Once a plant’s sex is determined, it can become a mother, clone, or breeding male, and can be harvested or even rejuvenated. Note: Plants show early male or female “pre-flowers” about the fourth week of vegetative growth. See “Pre-flowering” in Chapter Four and the sections here on pre-flowering male and female. Cloning, transplanting, pruning, and bending are all initiated when plants are in the vegetative growth stage.
Pre-flowering
Pre-flowers, described by Robert Clarke inMarijuana Botany as “primordial,” are the first indication of a plant’s sex. The pre-flowers grow at branch internodes just behind the leaf spur or stipule about the fourth week of vegetative growth, when the plant is six to eight weeks old. This is the point of sexual maturity, the first sign a plant is preparing for flowering–the next stage in life.
You can see pre-flowers with the naked eye, but a 10 to 30X magnifier will make viewing easier. You can accurately determine plant sex after eight weeks. Using this method, you can distinguish sex before inducing flowering.
Male Pre-flowering
Male pre-flowers are normally visible when plants are six to eight weeks old, after the fourth week of vegetative growth. The pre-flowers emerge behind the stipule at the fourth to fifth branch internodes and generally do not turn into full flowers. But, according to Bongaloid “a male plant will develop mature staminate flowers after prolonged periods of vegetative growth.”
Always wait to induce flowering until after pre-flowers appear. Inducing flowering with 12 hours of uninterrupted darkness and 12 hours of light before pre-flowers develop will stress the plant. This stress could cause peculiar growth, and plants might develop into hermaphrodites. Inducing flowering before pre-flowers form will not expedite flowering. In fact, flowering will occur at about the same time as if you had waited for pre-flowers to show!
Plants grown from seed under a 24/0 photoperiod will generally show pre-flowers after plants that are given a 18/6 day/night photoperiod. Once pre-flowers are distinguishable as male or female, plants can be induced to flower with a 12/12 day/night photoperiod.
A word of caution from bc-trichome-farmer : “Do not try to sex a seedling based on the very first pre-flower. Wait and make sure. The time between using a 25X (loupe) to spot the very first pre-flower and the plant dropping pollen is at least 10+ days away, so it’s safe.”
Female Pre-flowering
Near the end of normal vegetative growth, plants grown from seed develop pre-flowers. This is when female calyx formation initiates, and it is not contingent upon photoperiod. It occurs when a plant is old enough to show signs of sexual maturity, about the fourth week of vegetative growth, or six to eight weeks from germination. The pre-flowers emerge behind the stipule at the fourth to fifth branch internodes.
A pre-flower looks like a regular female flower; most have a pair of white fuzzy pistils. Pistils normally form after the light green seed bract part of the pre-flower has formed. Wait until pistils have formed to ensure the plant is a female and not a male. The pre-flowering stage lasts from one to two weeks. A little patience is in order now! Plants grown from seed under an 18/6 day/night photoperiod will usually show pronounced pre-flowers before plants given a 24/0 day/night photoperiod. And, under a 16/8 day/night regimen pre-flowers show more quickly and are often more pronounced. As soon as you can distinguish pre-flowers as male or female, plants can be induced to flower with a 12/12 day/night photoperiod.
Wait to induce flowering until pre-flowers have appeared. Inducing flowering with 12 hours of uninterrupted darkness and 12 hours of light before pre-flowers set will stress the plant. Such stress could cause strange growth, and plants may grow into hermaphrodites. Inducing flowering before pre-flowers develop does not make plants flower faster. Plants will flower about the same time as if you had waited for pre-flowers to develop.
JORGE CERVANTES
Published on Dolce Vita International 2
