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There's nothing like the taste of homegrown, sun-ripened tomatoes. The scent of tomato leaves in a warm greenhouse takes me straight back to childhood and memories of sneaking out to pick a handful of golden cherry tomatoes before school. Many people grow tomatoes from plants bought from garden centres or from roadside stalls, but if you want to grow some of the more unusual and heritage varieties (many of which are very tasty) you will probably need to grow from seed.
Don't be daunted, tomatoes are easy to grow. The main challenge you will face is resisting the urge to sow too many seeds unless you too intend to set up a stall at your garden gate.
How to grow a tomato plant - the basics
Growing tomatoes is an easy, fun and rewarding task. If you get the basics right, you will enjoy masses of fresh tomatoes that taste so much better than ones found in supermarkets.
Tomatoes are sub-tropical plants and therefore thrive in warm, sheltered and sunny environments; greenhouses are an ideal place for them. Tomatoes should preferably be grown in full sun. Tomato plants love rich and fertile soil and you will need to water them regularly as they are thirsty plants. Beware though, if you overwater them the tomatoes will rot or split. Once the first flowers have bloomed, tomato plants need feeding with high potassium feed such as Tomorite, once a week.
The growing season is from February (from seed) to July. If you are growing them from a plant, March/April to July.
Growing tomatoes from seed
If you plan to grow your tomatoes in a greenhouse, you should get the seeds sown in February in small pots or seed trays. Seeds for outdoor tomatoes can be started later, in March/April. They need to be at about 18C for germination, so place in a propagator or in a plastic bag on a bright window sill. Transplant when they have two true leaves, one seedling per 9cm pot. Keep potting on as the plant grows.
If you do buy plants, don't be tempted to put them straight outside. All plants, grown from seed or bought in, will need to be hardened off (left outside during the day for a week or two but returned to shelter overnight) before being planted outside. Whether in a greenhouse or outside you can grow tomatoes in pots (+30cm), a growing bag or in the ground. If you are growing cordon varieties, put the supports in place when the plants are small.
Growing Tomatoes in a Greenhouse
Greenhouses provide the ideal environment for tomato plants to thrive as they are sheltered and warm. You will need to be careful about excessive heat during the summer months so consider having blinds to help with this. As mentioned before, consider planting them in large pots (30cm should be fine) or grow bags.
TOP TIP: Grow basil plants in the same space as your tomatoes as these can help keep away pests and diseases, preventing them from ruining your tomato plants. Tomato and basil is a delicious flavour combination too.
Watering & Feeding Tomato Plants
Tomato plants are thirsty plants, but you can also easily overwater them causing rot. If possible, we recommend the ring culture method by placing the potted plants on capillary matting or pea gravel. By watering the matting/gravel the plant can absorb as much or as little water as it wants to.
You should feed tomatoes once a week and if you choose to use the ring culture method, feed them in the pot and not on the gravel or matting. This is because the water roots naturally grow downward and the feeding roots stay near the plant.
Cordon or Bush
There are two types of tomato, cordon (indeterminate tomatoes) and bush (determinate tomatoes).
Cordon varieties grow to about 1.8m and need supporting, by either tying to a bamboo cane or winding gently round a strong string attached to something above the plant - ridge or eave braces in a greenhouse are perfect for this. Cordon varieties need the side shoots pinching out regularly (these are the small shoots which appear between the branches and the main stem of the plant). This is so the plant can put its energy into producing the fruits.
Bush tomatoes are often grown in hanging baskets or pots and need no support. Remember, if they are in a hanging basket, they will need regular watering.
Cordon Tomato Variety
Caring for tomatoes
- Check the supports, especially as the fruit begins to ripen.
- Water regularly - irregular watering can cause Blossom End Rot (the end of the fruit hardens, goes black and becomes sunken) or split fruit.
- On Cordon varieties, remove the growing point once there are 7 trusses (groups of flowers) on greenhouse plants or 4 trusses on outdoor plants.
- Once flowers appear, start feeding once a week with a high potassium feed such as Tomorite.
- As the fruit begins to appear remove the bottom leaves to limit the spread of Tomato Blight or leaf mould.
If you grow some interesting varieties or if someone gives you some particularly delicious tomatoes, you may want to save seed for next year. It is easily done. Scrape the seeds out of a ripe tomato into a sieve and run under running water to remove as much of the gelatinous layer around the seeds as possible.
Empty the seeds onto two layers of kitchen paper and spread them out to dry. Write the variety on the kitchen paper (if you know it!) and leave to dry for a couple of days. You can then simply fold the paper and store in a labelled envelope in a cool, dark place until next spring – but do make sure you store somewhere mouse-proof. You can then lay the paper on damp compost, cover with a thin layer of compost and start the whole process again. The only seeds you cannot save are F1 hybrids. They will not come true from seed, so you won’t get the same fruit next year.
- Blossom End Rot and splitting fruits are the results of erratic watering. Try to maintain a regular watering and feeding schedule.
- Tomato Blight is a disease which is much more common in wet conditions and affects outdoor plants much more than greenhouse plants. The leaves become brown and mottled brown patches appear on the fruit. The plant should be disposed of immediately (not composted).
- Tomato leaf mould is a fungal disease which is more prevalent on greenhouse plants. Good ventilation and regular watering minimise the risk.
Want to grow your own sumptuous greenhouse tomatoes?
A Rhino Greenhouse is the perfect environment for all your plants.