How Often and How Much to Flood with a Hydroponic Nutrient Solution

The amount of nutrient solution you flood your plants with requires constant attention. I’m talking about an ebb & flow or flood and drain hydroponics system where the growing medium anchoring your plants is periodically flooded with nutrient solution which drains off after a specified time over and over in a continuous cycle.

How Long and How Often Should You Flood the Plants?

The goal is to flood the plants for about one-half hour, drain and then re-flood them again before the growing medium dries out. This provides the plant roots with a constant feeding from the damp, nutrient-saturated growing medium. Flooding too long or too often could drown your plants and not flooding enough could also kill them. It all depends on the density of your growing medium, the size of the growing container, the amount of heat and humidity in the air and the size of the plants. It sounds complicated but it really isn’t.

Dense growing medium will dry out slower than light medium and a small growing container will dry out faster than a larger one. Sunlight, heat, and a dry growing environment will evaporate water quicker and larger plants can drink an amazing amount of water per day.

I have an ebb & flow system with a growing container about 1.5 feet by 2 feet and 8 inches high which I keep in a hot and humid greenhouse. When the plants are young, I will flood them for one half hour every 4 hours day and night. I will also change this to flooding the plants one half hour every 3 hours during the day and one-half hour every 6 hours at night, as the temperature climbs in the summer and the plants grow.

I judge whether I ‘have it right’ by my plants. If they wilt during the day I increase the frequency of watering, checking first to make sure the medium is dry. If it is saturated, I decrease the frequency. In my second ebb & flow system I have 12 plants each in a 16 oz cup filled with medium. Since this tends to dry out very quickly, I flood this for 10 to 15 minutes on the hour, every hour.

So, there is really no set rule; for small containers start for 10 minutes every hour and for larger containers start with one half hour every 4 hours and adjust from there by watching how your plants react.

Larry Maki is an avid, self-taught hydroponics gardener with a passion for alternative types of gardening.

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