There are few things more delicious than the taste of a ripe tomato – they are synonymous with summer, topping burgers and salads as well as making up lovely sauces and condiments like salsa and ketchup.
As the most popular greenhouse crop, tomatoes grow extremely well indoors, though they require careful handling and maintenance to prevent the spread of disease and to pollinate their flowers.
But how do you select the best tomato varieties for a greenhouse – read on to find out!
- 1 How to plan a successful greenhouse tomato crop
- 2 Choosing the right location to sow tomatoes
- 3 Providing the proper climate to grow tomatoes
- 4 Selecting the best growing medium
- 5 Irrigation and drainage
- 6 How to select the best tomato variety
- 7 Types of tomato
- 8 Pollination
How to plan a successful greenhouse tomato crop
There are certain steps you can take to improve the likelihood of a successful tomato crop with a high yield.
As with any fruit or vegetable, the planning stage is nearly as important as the growing stage in ensuring success.
Choosing the right location to sow tomatoes
Tomatoes should only be grown in an environment free of pre-existing pests or diseases; if you see any signs of these issues, they should be treated before introducing your tomato plants.
It’s best to start small – if you’ve never planted tomatoes in a greenhouse before, you may want to begin with only a few plants to learn the ropes before investing in a large crop and potentially making costly mistakes.
Each plant will require a sunny spot at least four square feet around with good ventilation.
Providing the proper climate to grow tomatoes
Tomatoes need sufficient heat and light to produce fruit; in most regions, that will mean using a heating unit and grow lights during the winter months.
For optimal results, your tomato plants need 16-18 hours of sunlight. When the daylight hours are short, tomatoes may not receive enough natural light.
High-pressure sodium lights are best for tomatoes as they encourage flowering and fruiting, but for they are quite pricey for the average home gardeners; fluorescent grow lights will also work well and are considerably less expensive.
Tomatoes will grow best if the daytime temperature is 21° to 27° C (70° to 80° F) with night time temperatures of 16° to 18° C (60° to 65° F); you may want to test your greenhouse temperatures over the winter before introducing your tomato crop to ensure that the ideal climate can be maintained.
If possible, bring the temperatures into the lower end of the range on overcast days and into the higher reaches on clear and sunny days.
As tomatoes are highly susceptible to fungal growth, you should keep the relative humidity below 90% to prevent mould growth.
Ventilate the space regularly to introduce fresh, dry air to the greenhouse environment – especially on cooler mornings.
Selecting the best growing medium
Tomatoes thrive in any well-draining material – if you choose to plant them in a soil mix, it’s important to either purchase or make your own sterile soil.
If you don’t plan on installing an irrigation system, it’s best to use soil; adding sterile compost to enrich the soil can also be very beneficial.
Irrigation and drainage
Many growers use drip irrigations systems – these are essential if you’ve chosen a soil-less growing medium, but are nevertheless recommended for soil-based planting as well. The irrigation system can also be used to deliver fertilizer to the growing plants.
The irrigation system can also be used to deliver fertilizer to the growing plants.
Tomatoes also grow very well in hydroponic systems.
How to select the best tomato variety
You are, of course, looking for excellent flavour above all, but you should also consider the habits of your plants, as well as their ability to grow longer than the typical field crop season, to do well in lower-light conditions, and to set fruit without insect pollination.
You should also consider the projected yield of your plants, as well as their disease resistance.
As there are thousands of tomatoes varieties, it can be difficult to choose the right one for your greenhouse; typically, other local growers will be best informed on what works well in your region.
There are a few general guidelines that will apply to all regions:
- Tomatoes marketed specifically as greenhouse varieties will grow more successfully indoors, though any outdoor tomato plant can also be grown in a greenhouse – but greenhouse tomatoes will not always withstand outdoor growing conditions
- Varieties that are resistant to disease will be marked with either VF, VFNT, or A after the varietal name
Determinate vs. Indeterminate
Determinate varieties of tomato will stop growing at a fairly standard height with the stem ending in a fruit truss; these are also referred to a dwarf or bush varieties.
They don’t require pruning and are suitable for planting in containers if they’re staked or they can cascade from hanging baskets.
The most common tomatoes are indeterminate – these single-stemmed plants can grow up to 2.5 metres if the side-shoots are removed. They will need to be staked or cordoned to keep the plant upright.
Some varieties could be considered semi-determinate; they are similar to the single-stemmed indeterminate types but will produce shorter plants.
Types of tomato
These plants produce small fruit ranging from the size of a cherry to that of a golf ball.
Many cultivars, like the “Sun Gold” grow well indoors in less than 60 days from germination; they are typically sweet with red-orange skins and a traditional tomato flavour.
Though sometimes more difficult to grow and susceptible to pests or disease, heirloom tomatoes can nonetheless be a great choice for a more experienced greenhouse gardener.
Heirlooms varieties can take longer to mature as well and perform best in heated greenhouses.
One of the most common heirloom tomato plants, the “Beefsteak” variety produces a hearty tomato that is excellent for soups or sauces.
Many hybrid varieties have been bred to succeed in a greenhouse environment.
Several, such as the “Better Boy” grow quickly and are ready to harvest with 75 days of germination – and others like the “SuperSteak” produce exceptionally large fruit (than can weigh up to 1 kg).
Some hybrids, like the “Jumbo”, combine these qualities by producing large, juicy fruit in under three months from seed germination.
Tomatoes that are grown indoors cannot be pollinated by wind or insects. Some gardeners choose to keep bees for pollination but most manually pollinate their plants; after the petals have opened, they gently shake the plant or use an electric toothbrush or plant vibrator once a day to release the pollen.