A hydroponic growing environment is one where the plants grow in nutrient water instead of a garden bed. Drip irrigation is a common hydroponic system type for use with tomato plants. The benefit of growing tomatoes indoors with hydroponics is having fresh fruit available year round with a decrease in disease and insect damage to the plants. The tomatoes have increased flavor and size since the amount of nutrients provided to the plants is controlled.
Plant tomato seeds four to six weeks prior to setting the plants in a hydroponic system. Soak rock wool cubes in water to moisten and sow one tomato seed in each cube. Place the cubes in a growing tray and cover with a clear plastic bag or cover to create a greenhouse environment. Place the tray in a warm location with bright, indirect sunlight. Remove the cover once the tomato seeds have sprouted.
Grow the tomato seedlings until the true leaves are present and the roots are visible through the rock wool cubes. The plants will reach this stage in approximately 10 to 14 days. Monitor the moisture level in the cubes during this time to prevent the plants from drying out.
Transplant the seedlings into a hydroponic system by setting the seedlings into netted pots filled with hydroponic gravel or medium or into a larger rock wool cubes. Do not remove the tomato seedlings from the small cubes when transplanting. Space the plants at least 10 inches apart in the hydroponic system.
Test the nutrient water pH in the hydroponic system to verify that it is 5.8 to 6.3. Tomato plants grown in a hydroponic environment will produce nutrient deficiencies if the pH is too low or high. Lower the pH level by adding phosphoric acid or raise the pH with potassium hydroxide. Test the water pH every one to two weeks
Add hydroponic nutrients to the water as a food source for the tomato plants. Supply more nutrients each time water is added to the system to make sure the nutrient concentration stays at an adequate level.
Place metal halide growing lights over the hydroponic system to make sure the plants receive 16 to 18 hours of light each day. Mature tomato plants need light for long periods each day for fruit growth.