How To Grow Juicy Tomatoes In a Greenhouse?

A cool climate combined with a short growing season limits outdoor tomato crops. Growing tomatoes in a greenhouse can extend your growing season and the best part - is that it’s fun and easy!

In this guide, you will learn:

Why Tomatoes?

It’s rewarding to see tomatoes grow from seeds, see seedlings grow from two leaves, and eventually harvest succulent tomatoes. The benefits extend beyond the unbeatable flavor of homegrown and vine-ripened tomatoes.

  1. Tomatoes are annual plants and grow best in ambient temperatures between 18 and 32°C and soil temperatures of at least 12°C.
  2. Tomatoes are either vining or sprawling plants – the vining/indeterminate varieties require staking or caging.

  3. Early-season tomatoes take 50 to 60 days to reach harvesting whereas other varieties take up to 80 days to reach maturity. 

Popular greenhouse tomato varieties include Cappricia, Gardener's Delight, Sungold, Sweet Million, and Bull’s Heart.

 

  

Gorgeous and juicy tomatoes grown in a Planta Greenhouse by our customers all over North America. 

Benefits of Growing Tomatoes in a Greenhouse

The Planta-greenhouses are designed to make it easy to sow and grow tomatoes. You can cultivate tomatoes throughout the year beyond the short growing season in your area. Greenhouses will extend your harvesting window and get you a second (sometimes third) crop.

Greenhouses provide optimal conditions required right from the germination of tomato seeds to the completion of harvesting deliciously juicy homegrown tomatoes. 

  • Plant tomatoes whenever you feel appropriate. The timing depends on each person, your objectives, and the climate control tools at your disposal.
  • Growing tomatoes in your Planta Greenhouse always guarantees better yields throughout the year. Greenhouse-grown tomatoes produce 10 to 20 times more fruit compared to field tomatoes.
  • You are not limited to a single growing season during warmer weather. Grow your tomatoes throughout the year, even in the cold winter months. You will no longer be a victim of the whims of the weather/seasons.
  • Vertical production in the greenhouse makes it easier to prune, harvest, and work in the greenhouse. Inspect the roots of your tomato plants quickly and allow easy watering and the addition of nutrients.

  • Greenhouses protect your tomato plants from most pests, including birds and insects, inclement weather, and even malicious damage.
  • Nothing beats a vine-ripened tomato in quality and taste, and you can enjoy your tomatoes all year round.

 

  • Greenhouse tomatoes are comparatively more environmentally friendly and energy-efficient. 
  • Growing your tomatoes in a greenhouse is easy for both seasoned farmers and newbies.

Best indoor conditions to grow tomatoes.

High heat retention

Tomatoes do not grow well in temperatures below 16°C and above 27°C. Our galvanized steel and polycarbonate greenhouses can efficiently maintain these temperatures within a set range. 

Planta’s polycarbonate panels have high heat retention and keep the greenhouse pretty warm. However, to avoid ‘cooking’ the plants, you can add ventilation windows, which help provide additional air circulation and temperature control inside the greenhouse. Our windows come in automatic or manual options, depending on your needs. 

Using heaters and timers during the winter can help maintain proper indoor temperatures in the greenhouse to support your growing tomatoes. 

Automatic ventilation windows

Automatic ventilation windows don’t require any electricity or batteries and open/close depending on the temperature you set. You can set the window to open when the inside temperature reaches 17-25°C and close when the inside temperature is less than 17-25°C (you have control over the temperature). The maximum opening of the window reaches when the internal temp is 30°C and above. 

Ventilate the greenhouse to facilitate effective growing conditions for the tomatoes. Adequate ventilation is required to maintain the required humidity levels and prevent diseases from affecting your tomato plants. 

Tips for Growing Thriving Tomatoes in a Greenhouse

  • The right potting mix is essential for preparing individual pots. The pots must also have drain holes at the bottom to avoid waterlogging.

  • Sow the tomato seeds half an inch deep and one inch apart in your pots. Tomato seeds require an optimum soil temperature of 21-27°C (70-80°F) for germination. The warmth can be provided by placing the pots or flat near a bright window, on a heat mat, or under a fluorescent light. Germination starts from the 5th to the 7th day if the conditions are kept right.

  • The young seedlings continue growing at 18°C (65°F). Introduce a gentle breeze using a fan to help the seedling develop strong stems.
  • Two weeks after germination, the seedlings are ready for transplanting. To facilitate continued growth after transplantation, don’t disturb the roots.

  • Prepare the greenhouse for the growing season by ensuring all requirements are in place. Check that the galvanized steel frame and polycarbonate walls, as well as the seals, are intact.

  • Decide how you want to grow the plants. Tomatoes can grow in pots, troughs, or greenhouse borders. The containers should be deep enough and provide adequate soil for your tomato plants.

 

  • Ensure you have the right mix of nutrients in your growing medium to facilitate optimal growth. Add compost and tomato fertilizer to provide the required nutrients to your plants. Apply fertilizer at least 4 inches from the stems to prevent burning. Tomatoes require well-drained soils rich in organic matter and a pH of 5.5-6.8 for good yields. 

  • Transplant the seedling by burying the stem deeper into the soil. New roots will develop on the stem, making your plants sturdy.

  • The spacing of tomato seedlings should be between 90 and 120cm for the vining varieties. Use a B-1 solution to help your seedling withstand the shock of transplantation.
  • Water the newly transplanted seedlings regularly and throughout the growth process until harvesting. Tomatoes need plenty of water for good growth. The soil should be moist but not water-logged to prevent root rot and other issues. When watering, ensure that water does not get onto the leaves to avoid potential diseases.
  • Tomatoes require about 8 hours of sunlight per day. An advantage of polycarbonate is that it allows adequate sunlight for your plants. Tomato plants usually curl their leaves on a hot day. It isn’t a sign of disease or distress. However, wilting leaves early in the morning indicate that the plants need deep watering.
  • For support, use stakes, cages, or trellis as your tomato plants continue to grow. These supports help to keep leaves and tomatoes off the ground. Leaving the plants to sprawl on the ground increases the risk of pests and disease.

  • Staking tomatoes reduces the amount of growing space. That means that you can have more plants in your Planta greenhouse, irrespective of their size. Your stakes should be 1.8m in height.

  • Prune your tomato plants to retain two main and healthy stems. Remove side stems sprouting on your tomato plants after they have at least two leaves. The main stems are called leaders and trained on the stakes using elastic horticultural tape.
    • Pruning ensures that your plants are stronger and bear bigger fruits by getting rid of suckers growing on the main stems. The tomato plant focuses its vigor on fruit production through regular pruning.  
    • For semi-determinate tomato varieties, cut off the tips of the main stems when the plant reaches the top of the support stakes. Cut the top two leaves above the top-most flower truss.
  • Remove leaves and branches from the bottom 30cm of your plants as they grow taller. This will prevent the risk of soil-borne diseases and pests.

  • For good-quality fruits, limit the plants to six fruit trusses. Harvesting can begin when the tomato fruits are full, glossy, and starting to turn color. It is recommended that tomatoes be allowed to ripen on the vine.

Start Growing Juicy Greenhouse Tomatoes

Growing greenhouse tomatoes is relatively straightforward; however, that doesn’t mean you can simply throw seeds in the soil and wait for juicy tomatoes.

Mastering the care of tomato plants is crucial, as they require extra attention, particularly during the cold season. In addition, by adopting a staggered planting approach, you can enjoy greenhouse tomatoes throughout the year. 

Are you ready to start growing? Explore our resource library for more gardening tips, browse our DIY Greenhouse Kits, or reach out with any questions.

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