Guide to Growing Greenhouse Tomatoes

Growing healthy tomatoes in a greenhouse can be a challenge compared to traditional methods outside. However, when done correctly, growing tomatoes year round can have huge upside for farmers. Let’s explore some tips on how to grow the best greenhouse tomatoes. 

Advantages of Growing Tomatoes in a Greenhouse

Growing tomatoes in a greenhouse provides several benefits that aren’t possible with outdoor cultivation. There is a reason tomatoes are the most grown vegetable crop in greenhouses nationwide. Below are some key reasons to consider greenhouse tomato farming:

Year-Round Production

A greenhouse allows you to extend the growing season and produce tomatoes year-round. With temperature control and proper lighting, you can maintain an optimal environment for tomato growth regardless of outdoor weather conditions. This advantage is especially valuable in regions with harsh winters or short growing seasons such as the Northeast. 

Pest and Disease Control

By growing tomatoes in a greenhouse, you have greater control over the environment, which reduces the risk of pests and diseases. Greenhouse structures act as a physical barrier, keeping harmful insects and airborne pathogens at bay. This controlled environment also makes it easier to spot and address problems before they spread.

Improved Yield and Quality

Greenhouses allow you to create an ideal climate for tomatoes, resulting in higher yields and better-quality fruit. Tomatoes grown in greenhouses tend to have a more consistent shape, size, and flavor. With the ability to regulate water, nutrients, and light, you can maximize the growth potential of your plants.

Disadvantages of Growing Tomatoes in a Greenhouse

While greenhouse tomato farming has its perks, it’s not without challenges. The main drawback of greenhouse tomatoes is the overall cost, which can be upwards of $15 per tomato plant when grown in a greenhouse. Here are some of those potential drawbacks:

High Initial Investment

Setting up a greenhouse can be expensive. Costs include the structure itself, heating and cooling systems, ventilation, and supplementary lighting. This investment may be prohibitive for small-scale growers or those new to greenhouse farming.

Labor-Intensive Maintenance

Maintaining a greenhouse requires more effort than traditional outdoor farming. Regular tasks include monitoring temperature, humidity, and soil conditions, as well as managing pests and diseases that might thrive in enclosed spaces. Greenhouse farming also involves precise watering and pruning practices.

Energy Costs

Controlling the climate in a greenhouse can lead to high energy consumption, especially in colder climates. Heating during winter or cooling during summer can increase operational costs, which can offset some of the benefits of year-round production.

Best Soil for Greenhouse Tomatoes

The foundation of any successful tomato crop is healthy soil. Tomatoes grow best in well-draining, nitrogen-rich soil. Here is a breakdown of the advantages and disadvantages of various types of soil. 

Types of Soil

Loamy Soil: A balanced mixture of sand, silt, and clay, loamy soil provides excellent drainage, aeration, and nutrient retention, making it ideal for tomato plants.

Sandy Soil: While sandy soil drains well, it may require more frequent watering and nutrient supplementation to support tomato growth.

Clay Soil: Clay soil retains nutrients well but can become compacted, restricting root growth. Mixing clay soil with organic matter can improve its texture and suitability for tomatoes.

For greenhouse tomatoes, it’s essential to use sterilized soil to reduce the risk of introducing pests or diseases. Incorporating organic fertilizers with your loamy soil will help your soil thrive in greenhouse conditions. 

Be sure to perform a soil test to understand what nutrients your soil is lacking and then mix a granular fertilizer such as aged compost, and slow release feather meal and blood meal which are high in nitrogen which tomatoes need. 

Best Organic Fertilizer for Greenhouse Tomatoes

As a tomato farmer, you have the option to use fertilizers on the soil or directly on the tomato plants themselves. As previously discussed, it is crucial to understand what nutrients your soil is lacking in order to recommend the right fertilizers, but here are some recommendations for both granular and liquid fertilizers that do well on tomatoes and in the soil:

Granular Fertilizers for Greenhouse Tomatoes

Granular fertilizers are ideal for steady, long-term nutrient release, enriching the soil over weeks or months. Common options include:

Humus Compost: A rich compost great to mix with other fertilizer because of the magnetic force and ability to hold nutrients in the root zone. 

Gro Pro Plus (5-11-2): High in phosphorus, this pelletized dry fertilizer will give your tomatoes the phosphorus boost they need. 

Boron 10%: A slow release granular that will consistently feed the crop. 

Aragonite 35%: A quick release calcium source to help balance soil and feed the crop.

These fertilizers are applied to the soil, mixed in during planting or used as a top dressing. They help maintain balanced soil fertility and promote microbial activity, which is essential for nutrient cycling.

Liquid Fertilizers for Greenhouse Tomatoes

Liquid fertilizers provide immediate nutrient availability, making them an excellent choice for addressing specific deficiencies or feeding plants during critical growth phases. Examples include:

Fish Emulsion: A fast-acting, nitrogen-rich fertilizer that promotes leafy growth and can be used as a foliar spray or soil drench.

Seaweed Extract: This liquid fertilizer is rich in micronutrients and growth hormones, enhancing plant stress resistance and boosting flowering and fruiting.

Root Primer: A carbohydrate with organic acids that is a food source for microbes and give them the opportunity to thrive in the root zone.

Driving Trace Minerals into Tomato Plants

The key to successful tomato growth overall is making sure your crops are getting all of the nutritional elements they need, beyond just NPK. Foliar Feed Conductor-16, a soy protein nitrogen mixed with your micro nutrients, will help drive those traces into the plant. Trace minerals are easily absorbed through the leaves of the plant when using a plant derived nitrogen conductor.

For maximum fruit fill, consider using Potassium Sulfate 0-0-50.

Liquid fertilizers are typically applied via irrigation systems or sprayed directly onto plant leaves. They are particularly effective during periods of rapid growth or flowering. There are also liquid fertilizer mixes designed to include several combinations of the most beneficial nutrients to apply directly to your tomato plant such as Key Factor which includes magnesium sulfate, manganese sulfate, copper sulfate, cobalt sulfate, iron sulfate, zinc sulfate, and seafood proteins. This combination of organic nutrients will supply your tomato plants with the critical nitrogen and phosphorus needed for healthy and accelerated growth. 

Greenhouse Tomato Best Practices

To maximize your tomato yield follow these tips and best practices we have found to be critical for greenhouse tomato farmers:

Properly Tying up your Tomato Plant

Tomato plants need support as they grow to prevent their heavy fruit from weighing them down. Use soft twine, clips, or tomato cages to tie your plants gently to stakes or trellises. This practice not only keeps the plants upright but also improves air circulation and reduces the risk of diseases like blight.

Shading Your Tomatoes

While tomatoes thrive on sunlight, excessive heat or direct sunlight can damage the fruit and leaves. Consider using shade cloths during peak summer months to protect your plants. Shade cloths with a 30-50% reduction in sunlight intensity work well for maintaining optimal growth conditions.

Shade paint is a new way of keeping the greenhouse or tunnel cool and letting in more sunlight for better production. When using shade cloths, sometimes they can block sunlight and your plant will become more auxin dominate reaching for the sun.

Temperature Control

Tomatoes prefer consistent temperatures between 70–80°F during the day and 55–70°F at night. Use heaters, fans, or vents to regulate temperature and prevent extremes that could stress the plants. Automated systems can help maintain stable conditions with minimal manual intervention.

Leading Manufacturer of Organic Tomato Fertilizers

Keystone Bio-Ag is a team of regenerative agriculture consultants who not only guide farmers on sustainable farming practices, but have developed organic fertilizers that are designed to grow healthier, tastier crops without the chemicals. Contact the team at Keystone Bio-Ag if you are looking to improve your greenhouse tomato yield this season.