How to grow greenhouse hydroponic tomatoes

Hydroponic tomatoes

Planting density

When growing greenhouse tomatoes, it’s important to use the proper planting density. Greenhouse tomatoes need at least four square feet per plant or 10,000 plants per acre. Using a higher planting density will cause the yield per plant to decrease, while the yield per greenhouse will stay about the same.

Types of growing systems

  1. Nutrient film technique
  2. PVC pipes
  3. Sand
  4. Soil
  5. Troughs
  6. Rockwool
  7. Other aggregate media (e.g. peat moss, pine bark)

Large industrial greenhouses typically use rockwool. The recommended volume of aggregate medium is ½ cubic foot per plant.


Tomato flowers have both male and female parts within every flower. In an outdoor environment, field tomatoes are pollinated primarily by wind rather than by bees. Most of the flower’s pollen fertilizes the ovary within the same flower. In the greenhouse the wind is not strong enough to shake the flowers strongly enough to transfer the pollen so farmers seeking a profit should invest in an electric pollinator, while the hobbyist may not need the expense—an electric toothbrush or a good shake will do! For areas of 10,000 sq. ft. or more bumblebees should be considered.

The optimum temperature for pollination is between 70 to 82 F; and the optimum humidity level is 70 percent.

Temperature and humidity

The optimum growing temperature is between 70 to 82 F and at night a temperature of 62 to 64 F. The optimum relative humidity for greenhouse tomatoes is between 60 and 70 percent.


New transplants need about 50ml of water per plant per day. As a rule of thumb two quarts per plant per day are enough for most fully grown plants. Each watering should include hydroponic fertilizer, with a typical grower automatically providing 6 to 12 waterings per day once the plants are established—the number of waterings depends on the drainage properties of the growing medium.


In any hydroponic growing environment, fertilizer/nutrient application is one of the most important determinants of a successful crop. Know exactly how much of each fertilizer element is needed and how much is being applied. Also make sure to check the electrical conductivity (EC) and pH levels.

EC is a measure of the ability of a solution to conduct electricity, the more concentrated the fertilizer solution the more electricity it will conduct and the higher the reading—measured in millimhos (mmhos).


To maximize yield within the greenhouse prune tomato plants to a single stem. By keeping lateral stems more tomatoes will grow though they will be small and of poor quality. It’s better to have one main stem that bears larger, more uniform higher quality fruit. Prune early in the day when the plants are dry to allow plenty of time for recovery. Pruning while wet will increase the chance of disease.

Identifying nutrient deficiencies

Identifying nutrient deficiencies is critical to ensuring a successful tomato harvest. Keep an eye on the following telltale signs of nutrient deficiencies and address them swiftly!


Deficiency Symptom

Harm to Plant

Nitrogen (N)

Plants become spindly, leaves turn light green and yellowing of older leaves.

Restricted growth of tops, root and lateral shoots

Phosphorus (P)

Leaf color turns dull, dark green to bluish green. Purpling of petioles and veins under younger leaves.

Restricted and spindly growth.

Potassium (K)

Fruit ripens unevenly or shows blotchy green to yellow patches on red ripe fruit.

Fruit falls off plant before ripening, and may cause tomato to be spongy in texture.

Calcium (Ca)

Slight chlorosis to brown or black scorching of new leaf tips.

Restricted growth and blossom-end rot of the tomato.

Sulfer (S)

Leaves become yellowish green.

Stems increase in length but not in diameter.

Manganese (Mn)

Blossom buds turn yellow, and do not fully develop.

Some bloom buds on the flower cluster show incomplete development and do not develop into blooms.

Copper (Cu)

Leaves at the top of the plant wilt easily.

Splitting of ripe fruit, especially under warm temperatures.

image: Francesco Bartaloni via Compfight cc
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