Ebb and Flow

An ebb and flow system, or flood and drain system, gets its name from the periodic flooding and draining of nutrients from a reservoir. This system is one step up in difficulty from the DWC but can be broken down into just a few parts.

Ebb and Flow

The systems take advantage of the natural biologic process of the plants. Plants are placed in the flood table with their roots exposed. When the table floods, the roots soak up the nutrient solution and begin to crave air. Once the table drains, they soak up as much air as they can very quickly. With the roots exposed to air, they begin to dehydrate and dry out. Once they are ‘parched’ the table floods again and they binge on the nutrient-rich solution.

The Flood Table

The plant or flood table is a large, shallow container that typically sits on a tall stand. Plant seedlings are placed in net baskets and filled with a growing medium, such as LECA (lightweight expanded clay aggregate). The table needs to made of sturdy, waterproof material such as a thick plastic. White is the best color for the flood table since it reflects light back to the plants. This open air design does lead itself to higher maintanence since dust or even algea can dirty the table.

The Reservoir

Directly below the flood table’s stand is the reservoir. It connects to the table via a fill tube and a drain tube. Using a small aquarium pump, the nutrient solution flows up through the reservoir to the flood table via the fill tube. Then, the water drains back out via the drain tube. This allows the roots to dry and begin taking in oxygen. Adding a timer to the aquarium pump allows for a lot of control, so you can change the length and frequency of watering based on the gardens’ needs.

Cleaning the System

It is not uncommon for an ebb and flow system to begin growing algae. Improper cleaning of the algae can lead to mold and insects. There are also draining solutions used to ensure that the entire system sterilizes after each season and covers that can keep the flood table free from light that encourages algea growth.

The Positives

  • You can reuse your nutrient solution if you maintain cleanliness.
  • It is easy to build and once it is set up to operator’s specs then maintenance in simple.
  • It is exceedingly popular to grow vining plants like tomatoes and beans due to the ability to add trellises to the flood table.

The Negatives

  • Uncleaniness can lead to algea growth and destroy plants.
  • Minerals from the solution may build up on the bottom of the net baskets or growing media due to the flooding.
  • Those same minerals can block out the necessary nutrients to the plant and lead to deficiencies.