How to Grow Tomatoes Using Hydroponics

The tomato grows from a plant native to the Americas, which although it was thought to be poisonous when introduced to Europe in the 17th century, eventually became wildly popular worldwide. Hydroponics were not in use in those days as we know it – this is a 21st century guide to how to grow tomatoes using hydroponics!

Tomatoes are a healthy and delicious fruit that is used in many different dishes – pasta sauce, ketchup or salsa, soup, salad and much more.

Varieties of tomatoes

A member of the nightshade family of plants, there are now hundreds of varieties of tomatoes in many sizes and shapes and several shades of red, pink, orange, yellow, green, brown and purple. They can be sweet or tart – some even have a smoky flavour.

The ideal tomato is free of blemishes, plump and colourful, having ripened on the vine. But it’s difficult to get the perfect tomato when we’re relying on imported produce – many horticulturalists choose to grow their own tomatoes instead of buying them. However, for gardeners in cold climates, it’s rather difficult to grow tomatoes year-round, even in a greenhouse.

Growing them hydroponically can be an excellent solution (pardon the pun) to this issue.

What are Hydroponics?

Rather than planting in soil, a hydroponics system uses non-soil materials such as perlite, rock wool, or vermiculite to support the plant while a nutrient-rich solution delivers food directly to the roots.

It can be costly and time-consuming to set up and maintain a hydroponic garden – especially if you’ve never done so before, but there are many advantages to growing tomatoes hydroponically.

Advantages of Hydroponics

As hydroponic systems are only suitable for indoor gardens and greenhouses, the tomatoes can be grown year-round in a controlled environment; this minimizes the chance of disease or other pests such as aphids, worms or beetles. Using non-organic soil replacements creates a sterile environment and many soil alternatives can be sterilized and re-used year after year.

Studies have also proven that tomatoes grow faster in hydroponic gardens and they have a higher fruit yield – about 40 pounds of fruit or more can be grown annually per square foot.

How to Grow Hydroponic Tomatoes

Selecting and setting up the hydroponic system

Your first step will be to choose and set up the hydroponic system. Though several types of hydroponics have been used successfully on tomato plants, they tend to thrive best in drip-irrigation or ebb-and-flow systems.

Hydroponics stores or home improvement stores might sell a kit that requires everything you need to set up your own system; you can also purchase components separately and customize your hydroponic system for your needs.

Tomatoes plants will require plenty of light to thrive and natural light may not be sufficient, therefore plan for growing lights. The system should also be sealed off from other rooms so that the temperature and humidity can be regulated.

Starting tomatoes from seeds

Bringing in plants from the outdoors might introduce diseases or pests to the hydroponic environment. It’s therefore best to start planting from seeds whenever possible.

Place the seeds in a nursery tray with hydroponic growing materials instead of traditional soil. Some good choices are coconut coir mixed with clay “grow rocks”, rock wool, or perlite mixed with vermiculite. Before using the growing medium, it should be soaked in water with a pH level of 4.5 – most garden stores offer pH testing kits and the chemicals needed to adjust the pH level as needed.

Create a mini greenhouse

Place the seed under the material’s surface and keep the tray under a glass or plastic dome. This will help trap moisture in the environment and encourage the seeds to sprout.

When the plants have sprouted, remove the covering and ensure that the roots are completely covered by the starter material – if necessary, soak more growing medium to cover the roots. Then place the seedlings under a light source for at least 12 hours per day. 

Incandescent bulbs should be avoided whenever possible, as they produce more heat than other types of lighting.

Transplanting tomatoes

When the first true leaf – larger and different in appearance to the seed leaves – has grown and the roots begin to protrude from the bottom of the nursery tray, the seedling is ready to be transplanted to the hydroponic system. This typically takes 10-14 from sprouting.

You can maintain the same growing medium as used for the seedlings, or switch to an alternate material; choose whatever is best for your hydroponic system – for example, perlite will float to the top of an ebb-and-flow system and be carried away but is a great choice for Bato buckets and drip-irrigation systems.

The seedlings should be placed 10”-12” apart on slabs or within cloth sacks or net pots to allow the nutrient solution to circulate and reach the roots.

Caring for the growing tomato plants

The young plants will need between 16 and 18 hours of light daily for optimum results; then, turn off the growing lights and allow them 6-8 hours of total darkness. Hydroponic tomatoes can be grown using only natural sunlight, but the process will be slower.

During “daylight” hours, keep the room temperature between 18 and 24 °C and decrease it to 13 to 18 °C overnight. The nutrient solution should remain at between 20 and 22 °C.

Observation required

Observe the plants closely to ensure they’re receiving enough nutrients – look for wilted or discoloured leaves. Don’t allow the roots to become slimy or soaked, which may lead to root rot. You may also need to adjust the supply of nutrient solution as the plants begin to bloom and fruit since these processes can require additional water.

The water and nutrient solution should be changed regularly – every two weeks is usually sufficient but if your plants look unhealthy this can be done weekly. Monitor the pH level – which should be between 5.8 and 6.3 – and the electrical conductivity of the water; this is best way of measuring the nutrients in the water. An ‘EC meter’ should show 2.0 to 3.5; outside this range, the water should be at least partially changed.

Should I stake my tomato plants?

As the plants grow taller, they should be staked upright. This will encourage a higher yield and keep the fruit from touching the growing medium as they mature. If you need to prune your tomato plant, break off the stems with your hands rather than cutting them.

Pollinating the tomato plant blossoms

In your controlled environment, there will be no insect pollinators, therefore you must hand-pollinate the blossoms.

When the petals bend backward and expose the round pistil and the stamens – the long, thin sticks at the center covered with pollen – gently touch a soft paintbrush or toothbrush to each of the stamens, then brush the pollen onto the rounded end of the pistil.

The blossoms should be pollinated daily. When successful, the flower will wilt and begin to fruit.

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