Growing tomatoes in a greenhouse is a great way to enjoy homegrown produce all year round. But whether you’re starting seeds to plant outdoors or growing tomatoes to harvest within the greenhouse, there are a variety of techniques and tips to ensure a successful yield.
Although there are a variety of greenhouses that you can choose from, the basic concepts remain the same. The temperature inside the greenhouse must be regulated, the plants need to receive basic care including watering, fertilizing and pruning, and depending on how long you keep them in the greenhouse, they will need to be supported with a stake or trellis.
Regardless, it is a great way to get tomato seeds started and growing so that you can get a jump on garden season. No more trays of seedlings taking up valuable space in your home. Instead, you will have a dedicated space to grow not only tomatoes, but other vegetables throughout the year.
The Benefits of Growing Tomatoes in a Greenhouse
Growing tomatoes in a greenhouse offers the advantage of an extended growing season and higher yields compared to outdoor gardening. With the controlled environment of a greenhouse, you can enjoy fresh tomatoes even in the colder months.
They also significantly increase yields, with greenhouse-grown tomatoes producing 10 times more fruit than their outdoor counterparts. Beyond productivity, greenhouses protect your plants from pests like insects and birds, as well as from harsh weather conditions.
Additionally, greenhouses make efficient use of space by utilizing vertical growing systems, which can simplify your efforts of pruning, watering, and harvesting.
Common Greenhouse Tomato Varieties
Several types of tomatoes thrive as they grow in a greenhouse environment, offering a variety of flavors, sizes, and uses. Here are some of the best for greenhouse growing:
Gardener’s Delight is a reliable cherry tomato known for its sweet and juicy fruits, while Sungold stands out with its bright orange color and exceptionally sweet taste. For those looking for an abundant harvest, Sweet Million produces numerous small, flavorful tomatoes.
If larger, meatier tomatoes are your preference, Bull’s Heart is perfect for slicing and enjoying fresh. Lastly, Cappricia is a high-yielding variety prized for its excellent disease resistance, making it a reliable choice for greenhouse growers.
How To Grow Tomatoes In A Greenhouse
Starting Tomato Seeds in a Greenhouse
If you plan to transplant your greenhouse tomatoes into an outdoor garden, timing is key. Start tomato seeds indoors about 6-8 weeks before the last frost date in your area. This will give the plants enough time to grow to about 12 inches tall, which is an ideal size for outdoor planting.
Before planting the seeds, be sure that your small pots or seed trays have bottom drainage holes and then fill them with a quality potting soil. Sow the seeds about ½ inch deep into the soil.
Ideally it is best to use 2 inch deep seed starting containers so that you minimize the need to transplant the seedlings as they grow. (Product Affiliate Link: Juvale 2-inch Seed Starting Pots)
Tomato seeds require warm soil temperatures of 70-80°F for germination. You can achieve this by placing the pots on a heat mat or in a warm, sunny spot within the greenhouse. Under optimal conditions, seeds will germinate in 5-7 days.
Once the seedlings emerge, maintain a consistent temperature of around 65°F to encourage healthy growth. Use a fan to create a gentle breeze, which helps seedlings develop strong stems.
Then two weeks before outdoor planting, move the plants outside for 4-6 hours a day so they can adapt to the climate. See more details on how to harden off your tomato plants in this article: How To Harden Off Tomato Plants.
Choosing the Right Containers For Growing Tomatoes In A Greenhouse
If you plan to grow the tomato plants in the greenhouse throughout the season, you will need to choose a container that will allow the plants to thrive.
When using pots or containers, ensure they are at least 12 inches deep to provide ample space for root development. Containers should also have drainage holes to prevent the water pooling, which can lead to root rot.
If you’re growing tomatoes directly in the ground in the greenhouse, prepare the soil with a mix of compost and tomato-specific fertilizer. This will provide the necessary nutrients for your plants to to produce a strong plant base and a heavy fruit load. (Product Affiliate Link: Performance Organics Tomato Fertilizer)
Temperature Control
Tomatoes grow best in temperatures between 65°F and 85°F. During colder months, you will need to use heaters to maintain these temperatures.
In warmer weather, ventilation windows and fans help regulate the temperature and prevent overheating. Automatic ventilation windows are a great investment, as they open and close based on the temperature you set, ensuring your plants remain comfortable.
Sunlight Requirements When Growing Tomatoes In A Greenhouse
Tomatoes require at least 8 hours of sunlight a day. Greenhouses with poly panels allow adequate sunlight to penetrate while protecting the plants from harmful UV rays. If sunlight is limited, you can use LED shop lights or grow lights to supplement the natural light.
Watering Your Tomato Plants
Tomatoes need consistent moisture to grow well, but overwatering can be just as detrimental as underwatering. Water the plants deeply and regularly, ensuring the soil stays moist but not soggy.
As a general rule, water tomato plants when the top inch of soil feels dry to the touch. Avoid getting water on the leaves, as this can promote fungal diseases. In a greenhouse, the enclosed environment may increase humidity levels, so proper ventilation is essential to prevent diseases.
Supporting Tomato Plants
As your tomato plants grow in the greenhouse, they will need support. This will help to prevent the stems from breaking under the weight of the fruit. Just as when growing outdoors in a garden setting, you can use stakes, cages, or a trellis system to keep the plants upright. For indeterminate varieties, ensure the stakes are at least 6 feet tall to accommodate the plant’s growth.
Pruning & Harvesting – How To Grow Tomatoes In A Greenhouse
Prune your tomato plants regularly to promote healthy growth and larger fruits. Start by removing any leaves and branches near the base of the plant to reduce the risk of soil-borne diseases and pests.
Then as the plants grow remove any side shoots that develop and cross among other branches. This helps the plant focus its energy on producing fruit rather than excess foliage.
Tomatoes are ready to harvest when they just start to turn from green to blush in color. They will be firm to touch, and will continue to ripen once picked from the vine. Picking early will allow the plant to focus its energy on producing more fruit, giving you a bigger and better harvest.
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