Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

seeds to germinate. Viable seeds are preserved longer when vacuum-packed to remove all oxygen.
    Seeds with a thin, outer protective shell never truly go dormant, because moisture and air are always present within. This moisture and air cause hormone levels to slowly dissipate. Such seeds do not store well for a long time.

Seed Pests
    Seed pests become active when there is more than ten percent moisture content. When the growing medium contains more than fifteen percent moisture, fungi become active. Excess fertilizer slows seedling growth and promotes fungus attacks.
    Temperatures from 68-85°F (20-30°C) promote Pythium (damping-off) and rhixoctonia fungi. Cannabis seeds grow best at 78°F (25°C). Most fungi reproduce fastest in a temperature range of 68-86°F (20-30°C).
    Keep a wary eye on problems. Nutrient overdose burns leaf tips and fringes, which can look like damping-off to the untrained eye. Do not fertilize. Applying a fungicide now will make the problem worse.

Rooms like this supply a B.C. seed breeder with female breeding stock.

A lovely ‘Hempstar’ bud.

‘Northern Lights #5 x Haze.’

Chapter THREE
VEGETATIVE GROWTH

    Strong, healthy vegetative growth is the key to a heavy harvest.

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, CO 2 , 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.

This seedling is in the early stages of vegetative growth.

This ‘Euphoria’ female has been in the vegetative growth stage for more than two months.
    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.

Clones and Cloning
    Marijuana can be reproduced (propagated) sexually or asexually. Seeds are the product of sexual propagation; cuttings or clones are the result of asexual or vegetative propagation. In its simplest form, taking a cutting or clone involves cutting a growing branch tip and rooting it. Technically, cloning is taking one cell of a plant and promoting its growth into a plant. Marijuana growers commonly refer to a clone as meaning a branch of a cannabis plant that has been cut off and rooted.
    Cloning reduces the time it takes for a crop to mature. Productive growers have two rooms, a vegetative/cloning room, about a quarter the size of a second room used for flowering. Smaller vegetative plants take up less space than older flowering plants. For example, a 250- or 400-watt metal halide could easily illuminate vegetative plants and clones that would fill a flowering room lit by