In the modern way of farming through green-houses, tomatoes are the most grown crops. With good temperature management and enough sunshine, greenhouse growers in most areas of the planet will get two tomato crops annually. Indoor conditions do need a lot of careful handling to forestall diseases and to pollinate the flowers successfully. Most families in Kenya today use tomatoes in their daily cooking. As a farmer, this is a great opportunity, and with a greenhouse,you are sure of more.
Tomatoes grow best at daytime temperatures of 21–27ºC, and nighttime temperatures of 16–18ºC. Make sure you can maintain these temperatures in your greenhouse for the next several months before you plant.
- Ideally, bring temperatures to the lower end of this range on cold days, and raise them to the upper end (or even slightly higher) during clear, sunny days.
- You’ll also need to keep humidity below 90% to prevent excessive leaf mold. Ventilate regularly to bring fresh, dry air into the greenhouse, especially on cool, cloudy mornings.
Select certified tomato variety
There are varieties of tomato varieties, so for detailed information it’s best to talk to local extension officers. There are a few guidelines and tips that apply to all regions, however:
- Tomatoes marketed as greenhouse varieties are more tolerant of greenhouse conditions.
- The letters VFNT and A after the name mean the variety is resistant to disease.
- “Indeterminate” tomatoes grow and produce fruit indefinitely, taking advantage of the longer growing season inside a greenhouse. If you’re short on space, plant a “determinate” variety, which stops at a certain height.
Choose a growing medium
Tomatoes can grow in any well-drained soils. . You can use your preferred soil-less mix, or one of these options:
- Perlite bags or rock wool slabs are the cheapest options in many areas.
- Some growers prefer a 1:1 mix of manure and top soils
- Purchase sterile soil mix or make your own. Never use soil or compost from your garden without sterilizing. Choose this option if you do not want to install an irrigation system.
Most growers install drip tubing to deliver water to each plant. A fertilizer injector attached to the tubing can automate fertilizing as well.
- Tomatoes are also easy to grow in a hydroponics system.
Plant each seed in its own
Poke a ¼ inch (6mm) hole into each hole. Drop a single seed into each hole. Cover lightly with the potting mix.
- Plant about 10 or 15% more seeds than you plan on growing, so you can discard the least healthy seedlings.
Moisten with water or dilute nutrient solution
Use plain water for soil, or seedling nutrient solution for soil-less mixes. Either way, water until the mixture is just damp enough to press into a clump, with only a few drops squeezed out. Water regularly to keep the mix damp.
- A 5:2:5 nutrient solution that contains calcium and magnesium is ideal. Dilute the solution according to label instructions.
- Do not bring the seeds into the greenhouse until they’ve sprouted, so you can check for disease and pests. Provide plenty of sunlight and keep the temperature at 24–27ºC during the day.
Adjust pH and calcium levels
Before the final transplant, you may want to check soil pH, which ideally falls between 5.8 and 6.8.If your soil is too acidic, add about 1 tsp (5 mL) hydrated lime for each gallon (3.8 L) of potting mix. Besides raising the pH, this adds calcium that can prevent blossom rot later on.
- If your pH is fine, mix in gypsum or calcium sulfate instead to add calcium without changing the pH. Alternatively, just choose a fertilizer that contains calcium and apply every week or two.
- In a hydroponics setup, you can supply calcium by injecting calcium nitrate into the irrigation feed. This requires a second injector, as calcium nitrate cannot be stored with your main fertilizer.
Caring for the Tomatoes
Start fertilizing the day you transplant the tomatoes into their final pot. Use a complete fertilizer high in nitrogen (N) and potassium (K), such as a 15-5-15 or 5-2-5. Dilute and apply the fertilizer according to label instructions.
- Reduce fertilizer as the final fruits ripen. Do not fertilize in late autumn or winter, unless using artificial grow lights and reliable heaters.
Remove suckers weekly
Once a week, pinch off “suckers,” or side shoots that emerge where a leaf meets the main stem. Leave only the main bud at the top of the steam, plus the highest sucker below it. This trains the plant to grow upward instead of wide.
- If the top of your plant is damaged, the top sucker can become the new main stem.
Stake the tomato plants
Tie the plants loosely to stakes with twine to keep them upright. Use plastic garden clips where necessary to secure the twine.
- Commercial operations save on materials by stringing a wire over each row, with a support post every 20 ft (6m). Wrap the twine around each plant and fasten to the overhead wire.
Pollinate the flowers
Unlike many plants, a tomato can pollinate itself — but it needs some help. The pollen in a tomato flower is trapped inside a tube, and must be released through vibration. Since most greenhouses lack bees or high wind, you’ll need to act as the pollinator once flowers are fully open.
Prune leaves and fruit
Apart from weekly sucker removal, pruning is not necessary until the plant starts to fruit:
- Once fruit starts to grow, thin each cluster down to four or five fruits, removing the smallest or most misshapen. Very large fruits or winter conditions may require going down to three per cluster. Varieties with small fruits may not need any thinning.
- As the fruit matures, snap off older leaves from the lower clusters. This helps improve air circulation.
Harvest as late as possible.
The longer the tomatoes stay on the vine, the fuller and redder they become.
- Commercial growers typically pick a little early, when the fruit is 60–90% red, to allow for time in shipping.
If you need to know more about drip irrigation kits and how to apply it in your green house, contact us today.