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How To Grow Tomatoes In Your Greenhouse

tomato inside greenhouse

Growing tomatoes is no easy task and when done right you can have a yield that produces tomatoes for your entire neighborhood.

But, to make sure that your tomatoes grow properly you need to take the appropriate steps. Don't stress. We are here to help. 

In this post, we will go over everything you need to do to the perfect tomatoes in your greenhouse. Let's get started. 

 

1. Prepare Your Greenhouse

You will require the following items to start your tomato plants:

  • Soil nutrients
  • Tomato plant or seeds
  • String
  • Stakes

Include nutrients and fertilizer to ready the soil for your tomato plants. Be sure your tomato seeds are set beneath the soil by two to three inches. Stems of any pre-grown plants need to be underground as well.

To avoid the breakdown of the plant, fasten stem parts to a stake planted within the ground as the plant grows.

Sunlight, regularly warm temperatures, and ventilation are critical for tomatoes. Greenhouses can benefit from humidity. However, excessive humidity can hurt tomato plants and enable diseases. As a good rule of thumb, maintain ventilation and be sure that humidity never surpasses 90%.

Exhaust fans and open windows are your best bet for getting hot air out of greenhouses.

 

2. Choose The Right Soil 

Establishing fertile soil inside your greenhouse will help your tomatoes grow and prosper.

I recommend a potting mix that does not have any soil. Blends without soil will prevent weeds from growing in your garden. These mixes are also sterile so that you won't find any signs of bacteria or other pests inside.

Blends without soil are more consistent in their nutrient balance, acidification, and salinity. When soil is added to the blend, it increases the inconsistency and decreases the quality of the soil.

Potting soil and manure are common soil alternatives. Plotting soil has high variability and tends to compact after planting. I also recommend avoiding the use of manure when starting your tomato plants because it doesn't optimize growing.

I recommend using compost if possible. A soil mixture that is 100% compost is ideal for seed germination and starting tomato plants. Be cautious when purchasing compost because low-quality compost can cause low growth rates or even kill off your seedlings.

 

3. Select The Type of Tomato Your Are Going To Grow

There are typically three types of tomato plants: determinate, indeterminate, and semi-determinate. The types of tomato plant will determine how and when they grow.

If you are growing tomatoes in your greenhouse, I recommend you grow an indeterminate or semi-determinate tomato species. These types of tomatoes are great for greenhouses because they save space and grow vertically. This will allow you to grow other plants inside your greenhouse.

You can consider determining the type of tomatoes in a greenhouse if you want to grow tomatoes primarily. You can set up a shelf system to grow two layers of tomatoes. You typically will need a greenhouse that has 7-8 feet of headspace.

 

Determinate (DET)

  • Bush Tomatoes - only grow 1-3 feet tall.
  • Take up space horizontally than vertically. 
  • Produce a big crop and then stop producing for the remainder of the season. 
  • Ideal for those who need a large quantity at one time. 

 

Indeterminate (INDET or IND)

  • Plants grow vertically and can reach up to 10 feet tall. 
  • Typically require support to reach optimal potential. 
  • Grow and yield fruit throughout the year. 

 

Semi-Determinate:

  • Grow more horizontally than indeterminate types but less than determinate types. 
  • Grow and yield fruit throughout the year

 

Some of the best tomatoes to grow in a greenhouse include:

  • Beefsteak tomatoes
  • Campari tomatoes 
  • Cherry Tomatoes
  • Sun Gold Tomatoes 
  • Gardeners Delight Tomatoes
  • Ferline Tomatoes 
  • Black Opal Tomatoes 

 

4. Plant Your Tomato Seeds

Planting your tomato sees is the most important first step to growing your tomatoes.

As mentioned above, you should always use compost or a soilless blend to maximize your seedling growth.

You should also plant your seeds in a small pot. You want to plant two seeds per pot. This provides the optimal space for the roots to grow.

After about three weeks, you want to thin the seedlings to the strongest seed.

The light in your greenhouse is crucial to your seeds. If your greenhouse doesn't receive enough natural light, you should install an adequate lighting system.

As your seedlings grow, be certain that lights are four to six inches above them. The temperature of your seeds is also vital. Room temperature is not enough for germination.

Soil temperature should be 23C or 72-73F, and you can use heating mats or cables to help reach the ideal temperatures.

After ten days and once seedlings rise through the soil, bring the temperature down to 18C or 64F. Then, once four true leaves appear, further lessen the temperature to 15C or 59F.

Seedlings need feeding two times each week with liquid plant food or fish emulsion with quarter-strength. Spindly conditions can occur when seeds are deprived of fertilizer and necessary light. Also, an overabundance of heat can cause problems.

Tips for Tomato Seed Sowing

  • The pot’s top should be covered with seeds to begin the process of tomato seed sowing. Follow the tips below in order to avoid common first-time mistakes.
  • Make certain the seeds are evenly spaced out, not lumped together.
  • Ensure each seed has 0.5 inches of space between them.
  • Don’t overseed; this will hinder the seeds’ ability to grow.
  • Make sure sown seeds are moisturized evenly.
  • Avoid the deep burial of seeds; this is ill-advised.
  • Lightly cover the seeds with uniform levels of moisture.
  • Only use and sprinkle a fine soilless mix that is free of lumps onto seeds.
  • After seed sowing, use a pot plant marker to remember its contents.

 

5. Maintain Proper Plant Distances

The planting distance can have a huge impact on your tomato plants. You want to make sure there is enough space between each row and each plant.

The ideal distance between each row should be between two and three feet. Each plant should be between 17 and 24 inches apart from the center or stem of the plant.

If you are planting determinate plants, you might need additional space between each plant, while you can use a shorter distance for indeterminate plants.

Circulation is necessary for tomato plants to ward off diseases. Common diseases include:

  • Leaf spot
  • Early blight
  • Grey mold/Botrytis blight
Ventilation also makes a huge difference in high tunnels, greenhouses, and tomato plants, avoiding the following issues:
  • Decaying plants
  • Leaves turning yellow
  • Girdled stems
  • Moldy, fuzzy patches on living plant tissues

 

6. Rotate Your Tomato Plants 

Failing to rotate your tomato plants can lead to many serious issues. Many people think that using a greenhouse eliminates the need to rotate your crops. This is not the case; it's just as important in a greenhouse as in a garden. 

In fact, since greenhouses can be shut in, this makes crop rotation even more imperative. Years of tomato growth in the same spots can lead to the following issues: 

  • Heightened pest pressure
  • Deprivation of soil nutrients 
  • Uneven ripening
  • Fungus
  • Constant diseases
  • Absent productivity 

Crop rotation is vital to stopping and reducing pest infestations and plant diseases. 

In smaller greenhouses with limited crop rotation, you might need to replace the soil within the greenhouse's borders. 

Plants should also never be grown in the same environments for longer than 12 months. 

Each year, tomatoes should be rotated throughout your greenhouse. 

However, if your space is limited, then adhere to the following tips for the best results: 

  • Get annual soil tests
  • Include the proper soil amendments
  • Keep an eye out for seasonal diseases and pests
  • Use off seasons for soil solarization to eliminate pests/diseases hiding in the soil
  • Replace and replenish your soil 
  • Maintain your pH

 

7. Water Your Tomatoes

When watering your tomatoes, keep watering until the soil is damp, then you know you’ve watered enough. You should water your plants on a weekly basis.

For the best harvesting results, you’ll need to ensure that water stress isn’t an issue for your plants.

Drip Watering System

Drip watering systems deliver water directly to each plant. The drip system will deliver low volumes of water over a period of time.

You can install a drip watering system using a DYI option or a professional drip system. There are many drip watering systems that you can easily install inside your greenhouse.

Drip irrigation systems also create great levels of soil moisture without excessive evaporation. These systems should be checked on a daily basis. Daily checks will help prevent clogging.

DIY Drip Watering System

  1. To create a DIY drip watering system:
  2. Slice off the bottom part of a big soda bottle about 0.5 inches away from the bottom.
  3. Use a heated needle to puncture the bottle’s screw cap top.
  4. After reattaching the top to the sliced bottle, dig an 8-inch hole near your tomato plant.
  5. Put the top end of the bottle into the hole. After this, pour water into the bottom part of the bottle. The cap which was previously punctured with the needle will create an hours-long drip watering system.
  6. Create one bottle for each of your tomatoes.
  7. Make sure they’re also filled up on a daily basis. This will moisturize your tomato plants and the ground.

 

Other Watering Systems and Information

When using overhead irrigation, early morning watering is recommended. This will allow the leaves to get dried out by the sunlight. Avoid evening watering. This will create fungus and other problems since the leaves will stay wet overnight.

Rain gauges are necessary tools to ascertain the proper run time for irrigation systems. Using a rain gauge will inform you of how much water needs to be applied within the hour. Generally, 1.5 inches of water each week is best for tomato growth.

You can create your own rain gauge by getting an old yogurt container. Then, use a magic marker to identify every 0.5 inches going up the container. After you turn on the sprinkler, set a timer to learn how long it takes to get 0.5 inches of water. Use this as your base time. Double the time for one full inch of water.

Emitter flow rates and emitter counts are vital for calculating the flow rate of a drip irrigation system.

 

8. Monitor Your Temperature

Tomatoes love warmth. However, this comes with certain temperature limits to be aware of. Excessive heat and excessive coldness each create their own unwanted issues.

The following temperatures are best for your plants. Growing conditions can also be changed or managed as follows:

  • During early spring, use clear plastic to make the soil warmer. Remove this plastic ahead of planting.
  • During early spring, use black plastic to make the soil warmer. This warming process shouldn’t happen as quickly as it would with clear plastic. The black plastic can also remain on during summertime.
  • Shield young tender plants from cold nights and winds with a frost fabric.

For Seedlings 

  • 70-85 F is the best temperature for tomatoes during the day
  • 62-64 F is the best temperature for tomatoes during night time
  • Deficiencies in nutrients can happen if the temperature falls below 60 F

For Greenhouses

  • 56-58 F temperatures over multiple nights will make fruits rough 
  • Temperatures above 68 F will stop tomatoes from turning red
  • Temperatures below 55 F at night will hinder fruit setting and pollen development.
  • 90 F daytime temperatures will cause rotted or aborted blossoms by 10 AM

 

9. Feed Your Tomato Plants

Plant feeding is critical if you’re interested in fresh flowers, leaves, or fruit. Even when you have the greatest soil, awesome tomato crops still require feeding. 

Compost

Lots and lots of compost is critical for a wealth of tomatoes. In order to get the best crops, spread compost to the tune of 0.5 inches per square foot. After spreading the compost, you should no longer be able to see any soil. 

An awesome, healthy garden demands feeding your soil. The only real way to keep your soil healthy is by using compost. 

Fish Emulsion

Critical nitrogen sources and a variety of micronutrients comprise fish emulsion. In order to combine the proper concentration, mind the directions on the label. 

As a general rule of thumb, weekly fish emulsion feedings are best for tomatoes. Steer clear of compost tea; it is ineffective and useless. 

 

Organic Matter

Soil depends upon organic matter, especially when vegetable crops are involved. Organic matter needs to be added on an annual basis, due to the food it provides for soil microorganisms. 

No matter what you add to your garden, it is vital for you not to forget organic matter. This is especially critical in humid environments. As it turns out, the humidity leads to quicker consumption of organic matter. 

Following USDA Zone 4 hot summers, adding extra amounts of organic matter during the fall season is a must.

 

10. Use A Booster System

The secret to significant crop production is soil fertility. Thankfully, you can turn regular soil into super soil. Do this by creating raised soil beds with multiple inches of compost manure set in by three to five inches. After this, apply a top layer of soil over the manure. 

Ultimately, tomatoes will react well when supplied with compost manure or compost. However, it is still critical to make sure they’re given nutrition, watered, and appropriately cared for. 

 

11. Avoid Common Tomato Plant Problems

The following problems are quite typical when it comes to tomato plants: 

  • Incorrect planting: Different varieties have their own planting rules. Make sure your planted varieties are the proper distance apart from one another. 
  • Failure to rotate plants: Planting tomatoes in the same place for years on end will cause nutrient loss. It will also cause disease, uneven planting, and productivity interference. Each year, plant tomatoes in different areas. Be sure to include the necessary nutrients within fertilizer before replanting. 
  • Water deficiency: An abundance of water is a must for tomatoes. See the section on tomato plant care to learn more about watering. 
  • Excessive water: Excessive amounts of water will cause the tomatoes to break. 
  • Fertilizer with high levels of nitrogen: this will reduce tomato growth
  • Not preventing or taking steps to eliminate pest issues or diseases before they cause significant damage to your tomato plants. 

 

Frequently Asked Questions 

What to Do if You Find Diseases or Pests on Tomato Plants?

You should take immediate action to get rid of pests and diseases on your tomato plants. 

Aphids and whiteflies are the most common pest to infest tomato plants. Other common pests include: 

  • Nematodes
  • Cutworms
  • Flea beetles

If you suspect pests on your tomato plants, you want to take immediate action to eliminate them. Pests can destroy your tomato plants if not treated. Below are some steps you can take to eliminate pests. 

  • Whiteflies: Consider using ladybugs and sticky traps; use pesticides or get a spray hose to repel pests while watering.
  • Nematodes: Enact plant rotation. In only extreme cases, sterilize your soil. 
  • Cutworms: Set cones of cardboard around your seedlings
  • Flea beetles: secure young plants and use sticky traps; in extreme infection cases, use pesticides.
  • Aphids: Chop off infected leaves. Use insecticidal soap or ladybugs to eat away at aphids. 

To prevent diseases on your tomato plants inside your greenhouse, follow the steps below: 

  • Use proper greenhouse ventilation
  • Practice regular crop rotation
  • Remove weeds
  • Use high-quality fertilizer and soil
  • Water plants properly

 

How is Growing Tomatoes Different From Growing Other Vegetables?

Higher temperatures of 70-75 F are necessary for tomatoes, unlike other vegetables. Tomatoes also require sunlight, stakes and cannot share pots with other plants.

When grown in a greenhouse without airflow, tomatoes may require hand pollination. You can do this with mild stem shaking or even electric toothbrush vibration on the plant.

 

Can You Grow Tomatoes Year-Round?

Yes, you can grow tomatoes year-round. However, determinate tomato plants can only produce tomatoes during the growing seasons. Indeterminate and semi-determinate plants, on the other hand, can grow tomatoes year-round.

Tomatoes can be grown year-round with soil care and proper climate management.

 

Can Tomato Plants Be Overwatered?

Yes, tomato plants can be overwatered. Some common signs of overwatered tomato plants are as follows:

  • Leaf bumps
  • Tomato cracks
  • Lasting water puddles near the plant

 

When Should You Plant Tomatoes in a Greenhouse?

The best time to plant tomatoes in a greenhouse is six weeks ahead of the year’s final frost. This typically happens in April.

With that said, greenhouse growth generally poses less of a concern for frost. Therefore, you can even plant tomatoes in a greenhouse ahead of April if you’d like. If the greenhouse’s environment and climate are properly kept, you may plant tomatoes anytime.

 

Conclusion

Growing tomatoes is overwhelming if you don't know what you're doing. Fortunately, in this post, we laid out everything you need to know from start to finish to grow tomatoes in your greenhouse

Don't waste any more time. Start planting your tomatoes today, and before you know it, you'll have homegrown, delicious tomatoes at your disposal.