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

medium and becomes heavy and awkward to move.
    Marijuana roots develop and elongate quickly, growing down and out, away from the main taproot. For example, about midsummer, nurseries have unsold tomato plants that are still in small 4-inch (10 cm) pots and one-gallon (4 L) containers. The stunted plants have blooming flowers and ripe fruit. But few branches extend much beyond the sides of the container; the plants are tall and leggy with curled down leaves and an overall stunted, sickly appearance. These plants are pot- or root-bound. Once a plant deteriorates to this level, it is often easier and more efficient to toss it out and replace it with a healthy one.
    Roots soon hit the sides of containers where they grow down and mat up around the bottom. The unnatural environment inside the container often causes a thick layer of roots to grow alongside the container walls and bottom. This portion of the root zone is the most vulnerable to moisture and heat stress and is the most exposed.
    When soil dries in a pot, it becomes smaller, contracting and separating from the inside of the container wall. This condition is worst in smooth plastic pots. When this crack develops, frail root hairs located in the gap quickly die when they are exposed to air whistling down this crevice. Water also runs straight down this crack and onto the floor. You may think the pot was watered, but the root ball remains dry. Avoid such killer cracks by cultivating the soil surface and running your finger around the inside lip of the pots. Cultivate the soil in pots every few days and maintain evenly moist soil to help keep root hairs on the soil perimeter from drying out.

Large pots hold a lot of soil and require irrigation less frequently.

Large square pots are perfect for this hydroponic garden.

This room full of 3-gallon (11 L) pots is packed in so tight that you can walk on the pots.

Square containers are easy to bunch together when plants are small.

Deep containers are ideal for seedlings that will be planted outdoors.

Soil shrinks when dry; it causes a gap to form alongside the container wall.
     
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Selecting Container Size

    Allow 1 to 1.5 gallons (4 to 7 L) of soil or soilless mix for each month the plant will spend in the container. A 2- to 3-gallon (7.5-11 L) pot supports a plant for up to three months. 3- to 6-gallon containers are good for three to four months of rapid plant growth.
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Roots grow quickly and soon encircle the inside of the container.

Cultivate the top layer of soil with a fork to break up the crusty surface.
    Do not place containers in direct heat. If soil temperature climbs beyond 75°F (24°C), it can damage roots. Pots that are in direct heat should be shaded with a piece of plastic or cardboard.
    A 1 to 2-inch (3-5 cm) layer of hydro clay mulch on soil surface keeps soil surface moist. Roots are able to grow along the surface, and the soil does not need to be cultivated. The mulch also decreases evaporation and helps keep irrigation water from damaging roots or splashing.

Feeder roots grow near the soil surface, just under the expanded clay mulch.

Lightly cultivate the soil surface, so water penetrates evenly. Be careful not to disturb roots.
Green Roots
    White containers reflect light and keep soil cooler. Always use thick, white containers so light does not penetrate and slow root growth. If roots around the outside of the root ball start turning green, you know they are receiving direct light. Remedy the problem by painting the inside of the container with a non-toxic latex paint.

Roots turn green and grow poorly when they receive direct light.

These outdoor plants are thriving in Canada.

Chapter ELEVEN
WATER & NUTRIENTS

Introduction
    Water provides a medium to transport nutrients necessary for plant life and make them available for absorption by the roots. Water quality is essential for this process to work at maximum potential. The laws of physics govern plant water uptake. Applying these laws, a grower can provide precise, properly balanced components to grow outstanding marijuana indoors.
    Microscopic root hairs absorb water and nutrients in the oxygen present in the growing medium and carry them up the stem to the leaves. This flow of the water from the soil through the plant is called the transpiration steam. A fraction of the water is processed and used in photosynthesis. Excess water evaporates into the air, carrying waste products along with it via the stomata in the leaves.