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

is to cut a hole in the basement floor and install a dry well. Knocking holes in basement floors couldcause 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 (30-60 cm).

You can find this raised bed garden in the grow room at the Cannabis College in Amsterdam.

Install a dry well to evacuate excess runoff.
    At the Cannabis College in Amsterdam, Netherlands, they are growing in large soil beds set on a concrete floor. The basement beds are below sea level and filled with outstanding Dutch cannabis. They are able to treat the beds similar to outdoor soil beds, but when watered heavily, water runs out on the floor and it must be mopped up. They also have a problem with ventilation. The ambient climate is naturally humid and the extra water in the large basement increases humidity to above 90 percent, day and night. They employ a large extraction fan and a relatively small intake fan. Air is pulledthrough the long narrow basement room quickly and efficiently to evacuate moisture and lower the humidity. Even with this much soil, they have to flush individual beds at least once every four weeks to avoid nutrient buildup.

Flush containers with three times as much water volume of soil to leach out excess fertilizer salts. Flush containers every month to avoid many problems.

Flush containers with a mild nutrient solution every month.
    Much heat can be generated by decomposing organic matter, and it warms the room. 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.
    Another drawback to raised beds is that the crop will take a few days longer to mature than if it were grown in containers. But the longer wait is offset by a larger harvest.
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 (1.2 cm) holes per square foot of bottom. Most pots have twice this amount. To slow drainage and keep soil from washing out of the large holes, add a one-inch (3 cm) layer of gravel in the bottom of the pot. Surface tension created by the varying sizes of soil and rock particles cause water to be retained at the bottom of the container. Line pots with newspaper if drainage is too fast or if soil washes out drain holes. This will slow drainage, so be wary!
    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
    Popular pot shapes include rectangular and cylindrical. Growers prefer taller pots rather than wide, squat containers because the cannabis root system penetrates deeply. Of all the gardens I have visited, squat pots were few and far between. Growers I queried said squat pots may hold more soil for their stature, but they do not produce as extensive a root system.
    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