It's crucial to plan and prepare in advance if you are growing tomatoes in a greenhouse. Using the previous page, you will already have decided the method for growing tomatoes.

The next decision is when you want your tomatoes to be ready for eating. That, and the type of greenhouse you have, will determine when you should sow the seeds.
Indeterminate / vine / cordon varieties require support and training and this needs to be in place before the plants are placed in their final position.

 

WHEN TO SOW TOMATO SEED FOR GREENHOUSES

Many factors influence the growing of tomatoes in a greenhouse. These include the weather conditions in your area, how much light gets to the greenhouse and how much heat (if any) is available.

This article will assume (see assumptions page for this entire article) that you have a greenhouse with sufficient heat to avoid any frost from December onwards. If your greenhouse is "cold" (i.e. no heat is available) or "warm" (a minimum temperature of 16°C / 60°F can be maintained) then you will need to adjust the dates given below. Bad light availability will also affect the dates given below.

If you have a "warm" greenhouse then all activities can occur one month earlier than stated below. If you have a cold greenhouse then all activities should occur one two months later. Tomatoes will not tolerate any frost whatsoever.

TIMINGS FOR SOWING GREENHOUSE TOMATO SEED

as it grows.

 

 

Note 1 - Sowing greenhouse tomato seeds

Ensure the compost is moist then sow tomato seed on the surface of the lightly firmed down compost. Sprinkle on the compost so that the seeds are just covered then lightly firm down the surface. Cover the trays with paper or similar to block out the light.

Note 2 - Germination of  greenhouse tomato seeds

Where sowing lots of tomato seeds, they are best sown in trays because this reduces the amount of heated space they occupy. They need a temperature of about 18°C /65°F and this cannot be maintained in an unheated greenhouse during winter and early spring. If only sowing a few seeds then they can be sown directly into 12cm / 4½in pots.
Plastic pots are best. They can easily be cleaned after use, ready for next year.

Note 3 - Pricking out greenhouse tomato seedlings

To prick out seedlings, gently ease up the soil directly below them with something like a small plant marker. Gently ease the seedling (with any roots) out of the tray holding the leaves but not the stem which can very easily be damaged.

Note 4 - Greenhouse temperatures from pricking out to planting out.

The economical, ideal temperatures for growing tomato seedlings after pricking out is given in the table above. However, many, many factors affect what temperatures you grow your own tomatoes at between pricking out and planting in their final position. Factors such as available heating, levels of sunlight, what temperature zone you are in all have an influence on temperatures.

However, there are some definite "dos" and "donts" at this stage of growing tomatoes. These are:

 

 

 

 

 

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