Tomatoes are a staple in many people’s diets. In addition to being delicious, they are high in Lycopene, which is an antioxidant that has been shown to lower the risk of heart disease and some cancers.
Fortunately, tomatoes can grow hydroponically. Using hydroponic techniques allows people to grow tomatoes all year and provides the opportunity to experiment with several different varieties. However, hydroponic tomatoes are more difficult to grow than some other types of crops and may not be suitable for beginners.
The life cycle of a tomato depends on the variety. In general, it takes one to two months for plants to start producing fruit.
Grow From Seeds
Growing tomatoes from seeds are much less expensive than transplanting tomato plants grown from the store. Of course, using seeds adds to the growing time (8-14 days to germinate and 4-6 weeks to reach transplant size), but it may be worth it.
| Description | Cost | Unit Cost (Cost per Plant) |
| Cost of Seeds (50-pack) | $2.50 – $10.00 | $0.10 – $0.40 (Assuming 50% of the seeds germinate properly) |
| Cost of one tomato plant | $5.00 – $10.00 | $5.00 – $10.00 |
For example, there are a number of heirloom tomatoes that are available by seed that you cannot find as a seedling in gardening centers.
To grow tomatoes from seeds, first, soak Rockwool in water for 5-10 minutes. Make sure the water has a pH between 5.5 and 6.5. Remove the Rockwool from the water and allow it to drain for about five minutes. If your Rockwool cubes are too saturated, you could end up drowning your seeds.
Then put a seed in each cube of Rockwool and place the seeds under a propagation dome. I have seen some people use a plastic cake dome. This will trap moisture and encourage the seeds to germinate. Once you have added seed to each Rockwool cube, place the container on a heating pad.
After the seeds sprout, remove the cover and put the sprouts under a grow light (ideally a fluorescent bulb).
Use a Hydroponic System That Is Appropriate for Growing Tomatoes
Tomatoes need to be grown in a substrate rather than in the “water only” environment that is characteristic of nutrient fil technique (NFT). You can use a number of growing mediums of tomatoes including perlite, vermiculite, sawdust, Rockwool, and rice hulls.
Deepwater Culture (DWC), drip hydroponics, and Kratky hydroponics are techniques that are appropriate for growing tomatoes. You can build each of these systems using supplies from a hardware store or gardening center.
There are also a number of kits available for growing tomatoes hydroponically such as:
- Smart Indoor Garden Kit, Herb Garden Hydroponic Growing System, Xmas Led Desktop Growing Light for Home/Room/Kitchen/Office, Smart Indoor Herb Garden Grow Lamp for Flower/Fruit/Vegetable-(Blue)
- Deep Water Culture (DWC) Hydroponic Bubbler 8 Bucket Kit with 10″ Lids by PowerGrow Systems;
- SavvyGrow DWC Hydroponics Growing System-Kit – Large 5 Gallon 6 Buckets w/Air Pump Airstone – Complete Hydroponic Setup for Indoor Tomatoes, Peppers, Melons, Bean – Grow Super Fast at Home (6 Bucket);
- General Hydroponics Eco-Complete Power Grower GH4830;
These kits are available on Amazon.
Choose A Variety of Tomato That Grows Well Hydroponically
It is important to remember that a tomato variety that has a poor flavor when grown in the field will also have a poor flavor when grown hydroponically.
Some varieties of tomatoes will grow very fast and have a high yield. Unfortunately, these varieties may not always have a great flavor. If you are growing your own tomatoes, they might as well grow tasty ones.
Here is a list of tomato varieties that will grow well hydroponically (Resh, 2013).
| Tomato | Variety |
| Beefsteak | Caramba, Trust, Dombito, Caruso, Match, Blitz, Quest, and Geronimo |
| Cherry | Favorita, Cello, Conchita, and Juanita |
| Roma | Granadero, Naram, Savantas |
| Heirloom | Brandywine and Striped German |
| Tomato-on-Vine | Tradiro, Ambiance, Clarance, Tricia, Success, and Campari |
| Rootstock | Beaufort, Maxifort, and Manfort |
Keep in mind that if you are going to grow tomatoes in a greenhouse, you should grow vine rather than bush varieties. This is because these varieties will grow upwards and continue to produce fruit for several months.
When looking for tomato seeds, look for the “VFN” label. This label indicates resistance to verticillium, fusarium, and nematodes.
Maintain An Optimum Relative Humidity
In a greenhouse environment, tomatoes do best when the relative humidity is between 70 and 80 percent. This relative humidity should be maintained during the day and night.
The shelf life of tomatoes decreases when the relative humidity is above 80 percent. This is because a high relative humidity causes pollen to clump on the flowers of the tomatoes and cause poor pollination.
Relative humidity that is lower than 70 percent can cause the tomato plant to become infertile. When this happens, the fruit will set poorly.
Pay Attention To Micronutrient Levels
In general, it is not necessary to adjust the level of micronutrients when your tomatoes are growing. However, in areas with a lot of sunlight (like the southwestern region of the United States), plants require more copper, iron, manganese, and zinc.
The reason is that these micronutrients are an essential part of photosynthesis. However, you should be careful when increasing the level of these micronutrients. Make very small changes and diligently monitor the nutrient levels in your solution.
Choose the Appropriate Grow Lights
If you are growing your tomatoes inside, you should consider getting some grow lights. However, not all grow lights are created equal.
To understand which grow light you should use for your tomatoes, it is important to understand color temperature. Color temperature describes how various lamps emit light and is expressed in units of Kelvin (K).
Grow lights with higher color temperatures (5,000 – 6,000 K) emit the full light spectrum and are effective in all stages of growth. In contrast, grow lights with lower color temperatures (2,500 – 3,000 K) put off a reddish glow and are known to encourage flowering.
For tomatoes, it is best to use grow lights that closely mimic natural daylight conditions (color temperatures around 6,000 K). Fluorescent grow lights are the most popular type of grow light used by home growers. Specifically, compact fluorescent lights (CFLs) work well for growing tomatoes.
Your tomatoes should be exposed to about 16 hours of artificial light per day. Do not keep your grow lights on all day as plants need periods of darkness.
Watch Yellow Leaves
Tomato plant leaves turn yellow when they produce ethylene. This can occur because of a number of factors including an oxygen deficiency and a lack of light.
However, yellow leaves are to be expected in some cases. There is always some yellowing of lower leaves when the tomato fruit ripens upward on the plant. These yellow leaves should be removed to allow for better ventilation.
As lower leaves yellow below harvested fruit, they should be removed. A crack will develop where the plant is trying to shed the leave, so break the tomato leaves by hand rather than cutting them off. This will prevent exposure to diseases.
Yellow leaves may also be an indicator of a high pH value or low levels of nutrients. If the leaves of your tomato plants start to turn yellow, check your nutrient solution.
Make Sure Your Tomato Plants Have Enough Water
Each tomato plant in a hydroponic system needs at least 2.5 gallons.