Recent improvements in hydroponics have made flood and drain hydroponic systems affordable for hobbyists and home gardeners. Using hydroponic systems with artificial lighting or in a greenhouse allows crops to be grown year-round without regard to weather or season. Flood and Drain hydroponic systems are popular because they can grow a wide variety of plants using whichever growing medium is best suited to the plant. Flood and drain systems, also called ebb and flow systems, are reliable and customizable to the needs of the plant.
Flood and drain systems work by alternately flooding and draining the plant roots with nutrient solution. During the flood cycle, plants receive nutrients and moisture from the nutrient solution. When the nutrients drain away the roots receive oxygen.
A growing medium such as rockwool, clay pellets, perlite, sand, brick shards or gravel supports the plants and retains moisture so that the roots don't dry out during the drain cycle. Plants that like a lot of moisture do well in sand, clay, perlite or rockwool. Brick and gravel drain quickly and are best for plants that like a drier environment.
Flood and drain systems are ideal for starting seedlings and rooting cuttings. Small plants such as herbs, flowers and small potted plants do very well in the system. Larger plants need outside support in a flood and drain system.
Plants that do not like a lot of water or that can be damaged by high water levels should not be grown in a flood and drain system.
In a flood and drain system, the nutrient solution is constantly changing because the plants are removing nutrients and water. The nutrient solution must be pH adjusted to a level that will not harm the plants. For most plants, adjusting the pH weekly to between 6.0 and 6.5 is recommended.
Constantly flooding and draining the growing medium with nutrient-rich water allows salts to build up in the medium over time. Salt buildup can prevent the plant from obtaining needed nutrients and cause nutritional deficiencies. Occasionally flushing the system with plain water removes excess salts from the system.
The flood and drain system is very versatile. By choosing the right growing medium and regulating the time between flooding cycles, flood and drain systems can be tailored to the needs of the plants. Plants can be planted in individual pots containing the growing medium and different mediums can be mixed in the same system.
Flood and drain systems are useful in large scale propagation of plants. Cuttings placed in rockwool blocks or sand can be started under hydroponics and easily transplanted into any hydroponic or traditional soil-based growing system.
Flood and drain systems can be custom built to fit the needs of the gardener. A flood table can be made from a small plastic container or built from wood and waterproofed with plastic sheeting. Plans for do-it-yourself flood and drain systems are readily available and are inexpensive to build.
Once automated the system runs itself. The plants receive nutrition and water on a regular schedule. The system just requires a daily check and weekly maintenance of the nutrient solution.
Pump failure can be a serious problem in an automated system. The growing medium will hold moisture for a short period of time, but if the failure is not corrected within a reasonable time, the plants may suffer or die. Malfunction or clogging of the overflow valve could cause the water level to rise too high or stay flooded too long, drowning the plants.
Leaks in the system can also be a problem. Most gardeners using a flood and drain system indoors place plastic waterproofing on the floor and walls of the room to protect the room from water leaks.