How to grow tomatoes / RHS Gardening

Sow

How to grow tomatoes / RHS Gardening

Choosing what to grow

Tomatoes generally have two ways of growing:

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Cordon (or indeterminate) tomatoes grow tall, up to 1.8m (6ft), and require tall supports. They are great for growing in a greenhouse, but will also do well in a sunny spot outdoors, either in the ground or in large pots against a south-facing wall. They are useful when space is limited, as plants grow vertically, tall and narrow, and produce a heavy crop. They require regular maintenance – watering, feeding, tying to supports and pinching out side-shoots.

Bush (or determinate) tomatoes are shorter and wider, great for smaller gardens, pots and growing bags. Smaller types can also be grown in hanging baskets, with the stems trailing over the sides. These are the easiest type to grow and need little maintenance apart from watering and feeding. The stems don’t usually need support, except if heavily laden with fruit. 

Check seed packets or plant labels before buying, to ensure you get the right type to suit your needs. There are also lots of varieties to choose from, offering fruits of various sizes, shapes, flavours and textures. Fruit colours range from traditional red to dark purple, pink, orange, yellow or green, and even striped. There are heirloom varieties, grown for many generations, as well as modern, blight-resistant choices. There are miniature round fruits, elongated plum varieties, smooth uniform salad tomatoes and huge, wrinkled, mis-shapen beefsteaks, all full of flavour and with their own individual characters.

For varieties that will reliably produce good crops, look for those with an RHS Award of Garden Merit (AGM), which means they performed well in RHS growing trials. There are currently more than 40 AGM tomatoes to choose from – for a selection, see Recommended varieties, below.What & where to buy

Tomato seeds are widely available from garden centres and other seed stockists.Sow indoors 

Tomatoes are easy to grow from seed sown indoors in warm conditions. Sow from late February to mid-March if you’ll be growing your crop in a greenhouse, or from late March to early April if they’ll be outside. 

Fill a small pot with seed compost, water well, then sow three or four seeds on the surface. Cover with vermiculite and keep at around 18°C (64°F), ideally in a heated propagator, or cover with a clear plastic bag and place on a warm windowsill. As soon as seedlings appear – usually within a fortnight – uncover and place in as much light as possible, to prevent them growing thin and leggy. Potting on

After a couple of weeks, move the seedlings into individual pots: 

•    Fill small pots with multi-purpose compost and water well, then make a hole in the centre of each with a             dibber or blunt stick. 

•    Lift each seedling individually, using the dibber to support its rootball and holding it by a leaf rather than the       delicate stem, then lower it into the new hole. If the seedling is leggy, bury it up to the first pair of leaves,             then firm in gently.

Keep the plants in a greenhouse or on a well-lit windowsill, where the temperature is always at least 16°C (60°F), and water regularly. After about a month, they should be ready to plant into their final position, as soon as the first flowers open. 

Guide to sowing indoors          https://www.rhs.org.uk/advice/how-to-sow-seed-indoors

Guide to sowing veg seeds         https://www.rhs.org.uk/advice/profile?pid=619

Sowing tips                    https://www.rhs.org.uk/advice/beginners-guide/vegetable-basics/seed-sowing-techniques

 

Grow

How to grow tomatoes / RHS Gardening

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Watering

Water tomato plants regularly to keep the soil or compost evenly moist. Fluctuating moisture levels can cause problems with the fruit, such as splitting or blossom end rot (see Problem solving, below).

Plants in containers dry out quickly, so they may need watering daily in hot weather.Feeding

To boost fruiting, especially with plants in containers, feed every 10–14 days with a high potassium liquid fertiliser once the first fruits start to swell.Mulching

Lay a thick layer of mulch over the soil around tomato plants to help hold moisture in the ground and deter weeds. Use garden compost or well-rotted manure, but leave a gap around the base of the stem, to prevent rotting.Improving pollination

When growing tomatoes in a greenhouse, open the vents regularly to give pollinating insects access to the flowers. You can also lightly tap or shake the flowers when fully open to aid pollen transfer within the flower. Misting flowers with water may also help.Pruning & training

The two different types of tomatoes are treated differently – check your seed packet or plant label to see which type you are growing:

Cordon tomatoes are grown as tall, single-stemmed plants – they need tall supports and the side-shoots should be removed regularly.

Bush tomatoes are more compact and the side-shoots should not be removed. They may or may not need support, depending on how large they grow and whether the stems are strong enough to carry their crop of fruit.

For advice on training and pruning tomatoes, see our video guide https://www.rhs.org.uk/videos/advice/Growing-tomatoesCordon tomatoes   –             training up supports

Cordon tomatoes need support, usually either a tall sturdy cane or a vertical string coming down from an overhead horizontal support, such as a greenhouse roof, and anchored in the soil under the plant’s rootball. However, tomatoes don’t cling to supports or twine round them naturally, so must be attached by hand as they grow. If using a cane support, simply tie the main stem to it at regular intervals as it grows.

If using a vertical string, gently wind the string around the top of the main stem once or twice a week as it grows. When plants reach the top of their support or have set seven fruit trusses indoors or four trusses outdoors, remove the growing point of the main stem at two leaves above the top truss.Cordon tomatoes    –              removing side-shoots

Cordon tomatoes are best grown as single-stemmed plants. However, these vigorous plants naturally produce side-shoots from the joints where leaves sprout from the main stem. These side-shoots should be pinched out to keep plants growing vertically on just one stem. If they’re not removed, the side-shoots grow rapidly, forming a mass of long, scrambling, leafy stems that are difficult to support, produce few fruits and take up a lot of space. Removing the side-shoots is simple – every time you water, check the plant for any shoots sprouting just above each leaf, from the joint between the leaf and the stem. Pinch these out or snap them off.

 Bush tomatoes – providing support

Bush tomatoes are more compact and less vigorous than cordon tomatoes, and may not need supporting at all. But if they carry a heavy crop of fruits, the side-shoots may start to droop or be at risk of snapping. If so, simply add short vertical canes when required, tying in the shoots loosely to the cane.

Common problems

In a warm summer, tomatoes are easy to grow if they are well watered on a regular basis. However, problems can occur when conditions are not ideal, including

Blossom end rot
How to grow tomatoes / RHS Gardening

Dark blotches appear on the ends.

Remedy

Water regularly and not sporadically and never allow the soil to dry out.

Tomato blight
How to grow tomatoes / RHS Gardening

Disease that causes fruit and foliage rot, most common in wet weather.

Remedy

Select resistant cultivars.

Tomato leaf mould
How to grow tomatoes / RHS Gardening

Leaf mould can develop rapidly to cause significant yield loss in greenhouse-grown tomatoes. It is rarely seen on outdoor crops. Yellow blotches develop on the upper leaf surface. A pale, greyish-brown mould growth is found on the corresponding lower surface. Where the disease is severe the mould growth may also be found on the upper surface.

Remedy

Select resistant cultivars. Provide ample ventilation to indoor tomato crops.

Tomato splitting and cracking
How to grow tomatoes / RHS Gardening

Cracking or splitting usually does not affect the taste of the tomato, but split fruit left on the plant will often be infected by a fungus, such as grey mould and can cause a variety of physiological disorders.

Remedy

Control temperature and sunlight levels carefully. Feed regularly to maintain high soil fertility. Water to maintain a constant level of soil moisture.

Harvesting

How to grow tomatoes / RHS Gardening

Tomatoes start to ripen from mid-summer onwards, depending on the variety, weather conditions and fruit size. Smaller cherry tomatoes ripen more quickly than larger fruits, and greenhouse tomatoes usually start cropping earlier than those outdoors, and continue for longer, well into autumn. 

Check plants every few days and pick tomatoes individually, with the stalk still attached, as soon as they’re ripe and fully coloured.

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At the end of the growing season, lift outdoor plants with unripe fruit and either lay them on straw under cloches or pick the fruits and place somewhere warm and dark to ripen. Alternatively, put unripe tomatoes in a drawer with a banana, to aid ripening. Storage

Tomatoes are best eaten as fresh as possible. But if you have too many, then fully ripe tomatoes can be kept in a fridge for a week or so, to prevent them going mouldy. Try not to keep them refrigerated for long though, as the texture can deteriorate. Bring them back to room temperature before eating, to enjoy the full flavour. 

If the tomatoes aren’t yet fully ripe, leave them unrefrigerated to reach their peak of ripeness.

Surplus ripe tomatoes can also be cooked then frozen for use in pasta sauces, soups and stews.

 

Recipes

Nigel Slater uses large, ripe tomatoes for his delicious supper dish roast tomatoes with cheese and thyme.

Masterchef judge Gregg Wallace shares his recipe for tasty tomato tarts.

Recommended Varieties

Tomatoes — small fruits

‘Apero’ AGM

Exceptionally flavoured, very uniform, small, oval fruits. It’s a superb exhibition variety and has good disease resistance. A cordon type, so needs support.

‘Rosella’ AGM

Produces large crops of very sweet, dark pink-red cherry tomatoes, favoured by chefs for their rich, balanced flavour. A cordon type.

‘Sungold’ AGM

One of the most popular cherry varieties, it has golden-orange fruits with a sweet tangy flavour. A cordon type, it crops over a long period.

Tomatoes — medium fruits

‘Alicante’ AGM

A very reliable, heavy cropper that is widely grown. A cordon type, it fruits well both in a greenhouse and outdoors in a sheltered position.

‘Shirley’ AGM

A popular variety for growing in an unheated greenhouse. Excellent quality fruits with good disease resistance. A cordon type, so needs to be grown up a support.

‘Yellow Perfection’ AGM

Probably the best medium-fruited yellow tomato, this cordon variety produces heavy crops of tasty round golden tomatoes. 

Tomatoes — beefsteak

‘Brandy Boy’ AGM

Pink and thin skinned, the large fruits have a rich flavour. Bred from the popular heirloom variety ‘Brandywine’, this F1 hybrid offers bigger, earlier crops. A cordon type, so needs support.

‘Costoluto Fiorentino’ AGM

A deep-red, distinctly flattened, heavily ribbed Italian tomato. The large, early maturing fruits are particularly valued by chefs. A cordon variety, so plants need support.

‘Gigantomo’ AGM

Probably the largest-fruited variety available, with tomatoes up to 20cm (8in) across, so needs sturdy supports. Despite their size, the fruits have an excellent flavour and texture.

Tomatoes — trailing

‘Ildi’ AGM

Produces large trusses of small pear-shaped yellow fruits. If the trusses are picked and hung up, the fruits will last for weeks without deterioration. A cordon type.

‘Lizzano’

Vigorous plants with low sprawling growth, ideal for hanging baskets and containers. The deep-red cherry fruits ripen quickly in full sun.

‘Tumbler’

Best grown in hanging baskets, this trailing tomato is a really prolific cropper. It’s a small bush (determinate) variety. 

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