Hydroponic Tomatoes (and Cucumbers): How to Grow Them at Home

Hydroponic tomatoes grow in a soilless medium or in water, fed entirely by a nutrient solution, and they are one of the most rewarding crops you can grow that way. A healthy indeterminate vine keeps flowering and fruiting for months. The catch is that tomatoes are big, thirsty, long-season plants: they need a system with room for a large root mass, solid support, more light than lettuce and a feed that changes as they start to fruit.

This guide covers growing hydroponic tomatoes at home step by step, from choosing a system and variety to pruning and pollination, and adds cucumbers, which grow in the same setups with a few differences. If you keep fish, our aquaponic tomatoes guide covers the fish-fed version, which runs short of different nutrients.

Can You Grow Tomatoes Hydroponically?

Yes. Greenhouse tomatoes are widely grown without soil, in rockwool slabs, coir or perlite bags fed by drip lines. At home, the same principles work on a smaller scale. What matters is giving each plant enough root volume, a steady nutrient supply, enough light and a way to hold up several pounds of vine and fruit.

Determinate or Indeterminate?

Determinate (bush) tomatoes grow to a set size, fruit over a few weeks and stop. They suit a small indoor system or a single bucket. Indeterminate (vining) tomatoes keep growing and fruiting until conditions end the season, which is why greenhouse growers use them, but they need training up a string or trellis and regular pruning.

Choosing Varieties

Cherry and cocktail tomatoes are the easiest place to start: smaller fruit ripens faster and the plants forgive mistakes. Beefsteaks give the biggest fruit but need the most light and feed. Look for varieties bred for greenhouse or container growing, and for disease resistance codes on the seed packet. The aquaponic tomatoes page lists varieties that also suit hydroponics.

The Best Hydroponic Systems for Tomatoes

Dutch Buckets

A Dutch bucket is a container with a siphon elbow that keeps a small reserve at the bottom and drains the rest. A drip line feeds each bucket several times a day from a shared reservoir, and the return line carries the excess back. Fill with coarse perlite, a coir and perlite mix or clay pebbles; our clay pebbles guide covers the last.

A 5 Gallon DWC Bucket

The simplest start for one plant: a bucket, a 6 inch net basket lid, an air pump and stone. Our DWC hydroponic system guide covers the build. Keep the bucket shaded and cool, because a tomato's big root mass and warm water are the conditions root rot likes.

Nutrients, pH and EC for Hydroponic Tomatoes

pH

Writing in Greenhouse Grower in 2012, Robert Hansen of Ohio State University gave a pH target of about 5.5 to 6.5 for hydroponics, depending on the crop, and noted that growers often aim for the lower end. He also reported pH swings of 1 to 2 units in a day, so measure every day or two with a pH pen.

EC

Hansen said EC targets often fall in the range of 1.0 to 2.0 mS/cm, varying by crop, and advised avoiding EC above 4.0. Fruiting crops are generally run at the stronger end of the range for their stage, while seedlings start weaker. Follow your nutrient maker's chart for tomatoes and raise the strength gradually as the plant moves into fruit.

Choosing a Nutrient

Tomatoes need a lot of potassium and calcium once they fruit. A three-part liquid such as General Hydroponics Flora lets you shift toward bloom, and Masterblend's 4-18-38 kit is built around a tomato formula. Our best hydroponic nutrients guide compares them.

Light and Temperature

Light

Tomatoes need considerably more daily light than lettuce to flower and fruit well. A sunny greenhouse or a south-facing conservatory is the easiest place for them. Indoors, plan on a strong LED over a small area, and grow a cherry or dwarf variety rather than a beefsteak if your light is modest.

Temperature

Keep the air warm by day and a little cooler at night, and protect the plants from extremes: very hot or very cold conditions make flowers drop without setting fruit. Watch the reservoir too. A warm reservoir holds less oxygen, and that is when root problems start.

Pollinating Hydroponic Tomatoes

Tomato flowers are self-fertile, but the pollen has to be shaken loose. Outdoors, wind and bees do it. Indoors there is neither, so fruit set falls unless you help.

Vibrate the Flowers

Paul Betz, writing for High Mowing Organic Seeds in 2012, describes using a sonic electric toothbrush with the brush removed and a piece of wire on the shaft, held against the point where the flower meets the stem for about 2 seconds. He did it every day in his greenhouses. Tapping the truss or the support string with a finger works on a few plants.

A Fan Helps

A small fan that keeps the plants moving gently shakes some pollen loose and helps the leaves dry, which also reduces disease.

Hydroponic Cucumbers

Hydroponic cucumbers grow in the same Dutch buckets and DWC buckets as tomatoes and are often faster to the first harvest. The differences are in the variety, the training and how much water they use.

Choose a Parthenocarpic Variety

Parthenocarpic cucumbers set fruit without pollination. Greenhouse types such as long European and Beit Alpha cucumbers are bred this way, so you can skip pollinating entirely indoors. Some of them produce bitter or misshapen fruit if insects do pollinate them, which is one reason they are grown under cover.

Training Cucumbers

Train the main stem up a string like a tomato, remove the side shoots and fruit on the lowest leaves so the plant builds strength first, then let fruit set further up. When the stem reaches the top wire, let it hang down over it.

Feeding Cucumbers

Cucumbers grow fast and drink a lot, especially in warm conditions, so check reservoir levels daily. They need a balanced feed with plenty of nitrogen while the vine grows, then a fruiting formula. Keep pH in the same range as tomatoes.

Common Problems With Hydroponic Tomatoes

Blossom End Rot

A dark, leathery patch at the bottom of the fruit points to calcium not reaching it, usually because of uneven water supply or high humidity, not only a lack of calcium in the solution. Keep the feed steady and the air moving.

Flowers Dropping

Flowers that fall without setting fruit usually mean poor pollination, temperatures outside the comfortable range, or too little light.

Yellowing Lower Leaves

Some yellowing at the bottom of an old plant is normal. Widespread yellowing points to a nutrient that is too weak, a pH that has drifted, or roots that are struggling.

Root Rot

Brown, slimy roots with a bad smell mean oxygen-starved roots, usually from warm water. Cool and aerate the reservoir, and clean the system between crops.

Related: grow the fish-fed version with aquaponic tomatoes, try hydroponic strawberries, or start smaller with hydroponic lettuce.