There’s something very special about taking the first bite from a warm tomato you’ve picked from your greenhouse. Supermarket toms just can’t compare. So if you’re new to greenhouse gardening, sit back and prepare for your first time!
We’re going to look at growing vegetables in cool greenhouses, that is, greenhouses that are frost‐free but not heated. A cool greenhouse is ideal for sowing hardy seedlings that will later be planted out in your garden, as well as, during the summer, for growing a number of vegetables and herbs.
Tomatoes, peppers, aubergines, cucumbers, melons and herbs can all be successfully grown in a greenhouse. When choosing the seeds, look for those that specify their suitability for greenhouse growing. To ensure successful greenhouse vegetable gardening you want varieties that are bred to have the right qualities.
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In the Greenhouse
To grow vegetables successfully in a greenhouse you need a routine..
- Get into the habit of visiting your greenhouse at set times of the day (if you can).
- Check the temperature mid‐morning.
- Water the plants in the evening.
- Shut up the greenhouse last thing at night or when it begins to turn chilly.
Getting Hot
If the temperature in your greenhouse gets too high and stays too high, your plants will suffer. Growth and vigour will be affected.
- Through the summer, check the temperature in the greenhouse during the morning. If it’s getting too high, open the door and any vents you have. When you’re first getting used to your greenhouse you’ll want to check the temperature on a regular basis during the day using a thermometer kept inside in the shade. Once you’re used to your greenhouse, you’ll be able to adjust its temperature more effectively and less frequently in order to keep it as constant as possible.
- Don’t water during the heat of the day although if everything is looking very hot and bothered you can damp down your plants.
- Cover the glass with liquid shading to provide shade and prevent burn on the leaves.
- Plants don’t like stale air so make sure there is always adequate ventilation.
- It’s better to let the greenhouse get a little cool than to risk killing all your plants with excess heat.
General Seed Planting Advice
- Begin with a small pot and seed compost.
- Soak the compost and leave to drain.
- Place seeds carefully and well‐spaced on top.
- Sprinkle over more compost.
- Cover the pot with clingfilm to keep the compost damp and to aid germination.
Growing Tomatoes
Tomatoes are probably the most popular greenhouse vegetables, and the good news is that they’re easy to grow. There’s a huge variety of seeds available providing you with a choice of plum, large or cherry tomatoes. As we said at the start, choose a variety that is bred for greenhouse‐growing, that is, one that is a climber rather than a bushy plant.
Sow the seeds into 3″ pots in mid‐March. By May you should be able to transplant them into 12˝ pots or gro‐bags. As the seedlings begin to shoot up provide a bamboo cane for them to climb around and cling to.
In between the main stem and the sideshoots, tiny little shoots will appear. Pick these out to allow all the growth and goodness to go into the main flowering and fruiting shoots.
Feed regularly. Special tomato food is available at garden stores.
Be a busy bee
Help pollination along by tapping on the bamboo canes when the petals of the flowers are open and curved outwards.
Growing Peppers
Sow pepper seeds indoors in April in 3″ pots. When seedlings are large enough to handle transfer individual plants to 8˝ pots. Water regularly.
Chillies should be allowed to turn red before being harvested but then they can be frozen and stored in a small container in the freezer. Just a couple of plants should keep the average cook supplied for most of the year.
Growing cucumbers
When buying seeds, look out for the FI hybrid varieties, which produce female cucumber plants. If a flower is pollinated by a male plant, the fruit will be bitter‐tasting so you don’t want any of those males around!
Sow cucumber seeds in 3″ pots in mid‐March and transplant into 12˝ pots when seedlings are big enough. Provide a cane for the plant to grow up. After about 6 leaves have appeared, remove the growing shoot. Water well and feed regularly.
