Containers
Container preference is often a matter of convenience, cost, and availability. But the size, shape, and color of a container can affect the size and health of a cannabis plant as well as the versatility of the garden. Containers come in all shapes and sizes and can be constructed of almost anything- clay, metal, plastic, wood, and wood fiber are the most common. Cannabis will grow in any clean container that has not been used for petroleum products or deadly chemicals.
Clay fiber and wood containers breathe better than plastic or metal pots. Heavy clay pots are brittle and absorb moisture from the soil inside, causing the soil to dry out quickly. Metal pots are also impractical for grow rooms because they oxidize (rust) and can bleed off harmful elements and compounds. Wood, although somewhat expensive, makes some of the best containers, especially large raised beds and planters on wheels. Plastic containers are inexpensive, durable, and offer the best value to indoor growers.
Rigid plastic pots are the most commonly used containers in grow rooms. Growing in inexpensive, readily available containers is brilliant because they allow each plant to be cared for individually. You can control each plant’s specific water and nutrient regimen. Individual potted plants can also be moved. Turn pots every few days, so plants receive even lighting and foliage will grow evenly. Huddle small, containerized plants tightly together under the brightest area below HID lamp, and move them further apart as they grow. Set small plants up on blocks to move them closer the HID. Individual plants are easily quarantined or dipped in a medicinal solution. Weak, sick, and problem plants are easy to cull from the garden.
Grow bags are one of my favorite containers. Inexpensive, long-lasting grow bags take up little space and are lightweight. A box of 100 3-gallon grow bags weighs less than 5 pounds and measures less than a foot square. One hundred 3-gallon grow bags can be stored in two 3-gallon bags. Imagine storing 100 rigid pots in the same space!
Grow bags are very easy to wash and reuse. Empty out the soilless mix and submerge bags in a big container of soapy water overnight. Wash each one by hand the next day and fill with soil.
The potting soil sack can be used as a container. The moist soil inside the bag holds its shape well, and the bags expand and contract with the soil, lessening the chance of burned root tips that grow down the side of pots.
Fiber and paper-pulp pots are popular with growers who move their plants outdoors. The bottoms of the pots habitually rot out. Painting the inside of the fiber container with latex paint will keep the bottom from rotting for several crops.
Set large pots on blocks or casters to allow air circulation underneath. The soil stays warmer and maintenance is easier. Planters should be as big as possible but still allow easy access to plants. The roots have more room to grow and less container surface for roots to run into and grow down. With large pots, roots are able to intertwine and grow like crazy.
Grow beds can be installed right on the earthen floor of a garage or basement. If drainage is poor, a layer of gravel or a dry well can be made under the bed. Some growers use a jackhammer to remove the concrete floor in a basement to get better drainage. An easier option is to out a hole in the basement floor and install a dry well. Knocking holes in basement floors could cause water seepage, where water tables are high. When it rains, the water may collect underneath; the garden seldom needs watering, but plants are kept too wet.
A raised bed with a large soil mass can be built up organically after several crops. To hasten organic activity within the soil, add organic seaweed, manure, and additives. When mixing soil or adding amendments, use the best possible organic components and follow organic principles. There should be good drainage and the soil should be as deep as possible, 12-24 inches.
Decomposing organic matter generates much heat. Ventilation lowers heat and humidity, and helps keep the room free of pests and diseases. An organic garden sounds great, but it is a lot of work to replicate the great outdoors. Most organic growers opt for organic liquid fertilizers and a bagged commercial organic soil mix.
Drainage
All containers need some form of drainage. Drainage holes allow excess water and nutrient solution to flow freely out the bottom of a container. Drainage holes should let water drain easily, but not be so big that growing medium washes out onto the floor. Containers should have at least two half-inch holes per square foot of bottom. Most pots have twice this amount.
Put trays under containers to catch excess water. Leaving water-filled saucers under pots often causes root rot. To avoid water-logging soil and roots, set containers up an inch or two on blocks when using trays.
Nursery trays used for rooting cuttings and growing seedlings must have good drainage throughout the entire bottom. Once clones and seedlings are in place in the tray, the tray should always drain freely with no standing water in the bottom.
Container Shape, Size, and Maintenance
The volume of a container can easily dictate the size of a plant. Cannabis is an annual; it grows very fast and requires a lot of root space for sustained, vigorous development. Containers should be big enough to allow for a strong root system, but just big enough to contain the root system before harvest. If the container is too small, roots are confined, water and nutrient uptake is limited, and growth slows to a crawl. But if the container is too big, it requires too much expensive growing medium and becomes heavy and awkward to move.
Cannabis 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 pots and one-gallon containers. The stunted plants have blooming flowers and ripe fruit. But few branches extend much beyond the sides of 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 sir whistling down the crevice. Water also runs straight down this crack and onto the floor. Avoid such 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.
Do not place containers in direct heat. If soil temperature climbs beyond 75 degrees Fahrenheit, it can damage roots. Shade pots that are in direct heat with a piece of plastic or cardboard.
A 1 to 2-inch layer of hydro clay mulch on soil surface keeps soil surface moist removing the need to cultivate. The mulch also decreases evaporation and helps keep irrigation water from damaging roots or splashing.
Selecting Container Size
| Plant Age | Container Size |
| 0-3 weeks | root cube |
| 2-6 weeks | 4-inch pot |
| 6-8 weeks | 2-gallon pot |
| 2-3 months | 3-gallon pot |
| 3-8 months | 5-gallon pot |
| 6-18 months | 10-gallon pot |
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.