Ebb and Flow Gardens

Marijuana Horticulture

by Jorge Cervantes

Ebb and flow (flood and drain) hydroponic systems are popular because they have a proven track record as low maintenance, easy to use gardens. Ebb and flow systems are versatile, simple by design, and very efficient. Individual plants in pots or rockwool cubes are set on a special table. The table is a growing bed that can hold one to four inches of nutrient solution. Nutrient solution is pumped into the table or growing bed.

The rockwool blocks or containers are flooded from the bottom, which pushes the oxygen poor air out. Once the nutrient solution reaches a set level, an overflow pipe drains the excess to the reservoir. When the pump is turned off and the growing medium drains, it draws new oxygen rich air into contact with the roots. A maze of drainage gullies in the bottom of the table directs runoff solution back to the catchment tank reservoir. This cycle is repeated several times a day. Ebb and flow systems are ideal for growing many short plants in a Sea of Green garden.

Flood the table to half to three quarters the height of the container to ensure even nutrient solution distribution. Avoid lightweight mediums such as perlite that may cause containers to float and fall over.

A large volume of water is necessary to fill the entire table. Make sure the reservoir has enough solution to flood the reservoir and still retain a minimum of 25 percent extra to allow for daily evaporation. Replenish reservoir daily if necessary. Do not let nutrient solution stand in the table for more than a half hour. Submerge roots down in the depleted oxygen environment.

Flood the table when the medium is about half-full of moisture. Remember, rockwool holds a lot of moisture. Irrigation regimens will need to change substantially when temperatures cool and light is lacking.

Ebb and flow tables or growing beds are designed to let excess water flow freely away from the growing medium and roots. When flooded with an inch or more of nutrient solution, the growing medium wicks up the solution into the freshly aerated medium.