how to plant, grow & care for tomatoes
complete growing guide
We grow loads of tomatoes at Perch Hill as they are so versatile in salads, pasta dishes and a whole host of Mediterranean recipes. They are also full of vitamins and minerals, making them superfoods in my book. They are so much tastier picked fresh and warm from the garden than out of a supermarket fridge. There is a delicious variety for almost every purpose and we have selected the best out of a bewildering range that you can order as seeds, seedlings or large plants ready to go straight into your garden, greenhouse or polytunnel.
- Common name: Tomato
- Latin name: Solanum lycopersicum
- Type: Half-Hardy Annual
- Height & Spread: Up to 2m tall and 1m spread for cordon tomatoes
- TLC rating: Easy
- Aspect: Sunny and sheltered, preferably in a greenhouse
- Spacing: 60-90cm
- Yield: Up to 2kg depending on variety
- Suitable for pots: Good in pots
- Grow in a greenhouse? If possible, although some varieties are good outside
how to grow tomatoes
where to grow tomatoes
Soil type: Tomatoes like a rich moisture retentive soil and will need regular liquid feeds once they start to flower and fruit. As you are most likely to be growing these in pots or grow bags you have the chance to renew the soil completely each year. A peat free multi-purpose compost will be fine, or make your own mix by adding home-made compost or farm-yard manure to get the plants off to a flying start.
Aspect & position: Tomatoes need as much sun as they can get. A polytunnel or glasshouse is ideal, but some varieties are very happy outside in a sunny sheltered spot, you can even grow ‘Tumbling Tom’ in a window box or hanging basket.
when to plant tomatoes
A wise man once told me that you should plant out tomatoes when it's warm enough to eat outside without majorly wrapping up, and I've never forgotten this useful advice. It's always a lovely moment when tomato-sowing time arrives: it means that spring is here, or is, at the very least, just around the corner.
If you have space to grow tomatoes from seed under cover, sow them in late February or early March, somewhere warm and cosy. You'll then have decent-sized tomato plants, ready and waiting to go into greenhouse beds or growbags at the end of April, when very cold nights are unlikely and you can stop mollycoddling your nascent plants.
If you can only grow tomatoes from seed outside, wait another few weeks. You don't want to put your plants out when there is still a chance of night-time temperatures plummeting unexpectedly. Here in Sussex, that means the end of May. It’s best to sow just seven or eight weeks before you can plant them out.
how to plant tomatoes
growing tomatoes from seed
You can sow tomato seeds in a seed tray in the usual way and prick them out into individual small pots once they have two true leaves. However, I prefer to sow two tomato seeds into coir or Jiffy pellets, and put them on to my heated polytunnel benches (although keeping them moist somewhere warm will do).
Once their roots have filled the pellet, I tear off the net and pot them on into a 9cm (3.5in) pot. The roots will fill that two or three weeks later and I then plant them in a two-litre pot, supporting them with canes and string stuck in at their side. Once they've filled that, they're ready for final planting.
planting tomato plants in a greenhouse
For unheated greenhouses, final planting can take place in mid-spring. We try to plant ours in Sussex in our greenhouse in the last week of April.
For containers, use a large pot at least 30cm wide and deep but the bigger the better and fill with a good quality, peat-free compost. For grow bags, allow two plants per bag. Alternatively, you can use our ring culture pots which allow you to provide fertiliser to the feeding roots and water to the deeper water transport roots.
planting tomatoes outside
For growing outside, first of all choose a variety that is happy in our climate. 'Noire de Crimèe' comes from Russia and is more than happy here – it also tastes delicious, ‘Gardeners Delight’ is another stalwart and we’ve had good results outside with ‘Sungold’ and ‘Stupicke Polne Rane’.
You will still need to gradually acclimatise plants (“harden off”) to outdoor conditions before planting out in early summer. You will also need a sturdy structure to support cordon varieties (i.e. most of the ones I grow apart from the bushy cherry tomatoes such as ‘Tumbling Tom’ or ‘Micro Cherry’). Alternatively use strings or canes attached to a south facing wall.
Add plenty of compost or well-rotted manure prior to planting and create a shallow circular reservoir around the plant to help retain water or use ring culture pots. Leave 60-90cm (24-36in) between each plant and plant them deep, sinking them to a depth of 0.5cm below the seed leaves.
how to care for tomatoes
watering & feeding
Under cover or outside they need staking, regular watering and weekly feeding for best results. Water the soil, not the plant, tomato leaves and stems dislike getting wet.
For cordon varieties you also need to pinch out any side shoots that develop between the main stem and where the leaf branches out as they divert valuable energy from the developing fruits and will end up as an unruly sprawl. Bush tomatoes (e.g. ‘Micro Cherry’) will not need such attention but you will need to allow plenty of space for them to spread.
For the large-fruited varieties you will need to pinch out the tops once they have set 5 or 6 trusses of fruit.
Companion planting works well with tomatoes. Try basil underneath as a sacrificial planting – white fly is drawn to it rather than your tomatoes – or try garlic, nasturtiums or tagetes to repel aphids.
Cordon tomatoes fruit over a long period. You should be picking tomatoes in July and continue harvesting from the cordons until October, some like ‘Gardener’s Delight’ and ‘Sungold’ might even carry on until November. At the end of the summer, any unripe tomatoes can be picked and placed next to a banana – the ethylene released helps them to ripen.
Tomatoes can be kept at room temperature for 4-5 days (they will lose their flavour if kept in the fridge), and will freeze well.
- Sow seed in late February through to April.
- Plant out under cover in April.
- Plant outside in May/June
- Stake, water and feed regularly
- Pinch out the side shoots of cordon varieties and stop the growing tip at 5 trusses for large fruiting types.
- Pick fruit as it ripens and enjoy.
- Pick any unripe fruit and bring indoors to ripen if frost is forecast
- Preserve ripe fruit by freezing or bottling, turn green tomatoes into chutney.
- Tidy away and compost old plants to prevent disease next year.
pests, diseases & common issues
Seedlings can suffer from “damping off”, a fungal disease that attacks in overly humid conditions or if the pots or seed trays are not clean. Make sure seed is not sown too thickly to allow good air circulation.
sciarid fly larvae
Sciarid fly larvae can attack the roots of young seedlings which will suddenly cause the plant to keel over and die. This can arise if grown in a greenhouse that has harboured them from the year before, so hygiene is key! Make sure the compost is fresh when you sow your seed.
aphids & whitefly
Aphids and whitefly can cause problems in the greenhouse and polytunnel. Companion planting can help (basil, garlic, nasturtiums or marigolds), there are also biological controls such as encarsia wasps which will predate on the pests.
Blight is a major problem for tomatoes grown outside as it is an airborne fungus that prefers damp, cool conditions and is very hard to prevent if it is in your area. Blight causes dark blotches on the plants that will spread onto the fruits and eventually kill the whole plant.
There are some good blight resistant varieties (e.g. ‘Stupicke Polni Raine’). Indoor crops should suffer less from this disease which is also common in potatoes, so try to keep plants apart in the garden.
Keep an eye open for dark blotches on the leaves, stems and fruit and remove immediately. As the season progresses the lower leaves can be removed to allow better air circulation and ripening. Once all the fruit has set you can remove more of the leaves thus helping to avoid the problem.
tomato blossom end rot
Blossom end rot is caused by irregular watering that can lead to a calcium deficiency. Try to keep the soil moist by watering every day if grown indoors (outdoor tomatoes rarely suffer from this disease unless the soil is really dry). Also try to make sure there is good ventilation in the greenhouse or polytunnel.
tomato leaf mould
This is another fungal disease that can affect tomatoes grown indoors, but is rarely seen outside. Make sure there is plenty of ventilation and avoid getting water on the leaves – the lower leaves can often be removed to ensure this does not happen.
You might find that you are getting green patches on the shoulders of your tomatoes. This is known as ‘Green back’ and can be caused by too much bright light and heat. Look into some greenhouse shading for the height of summer.
why are my tomatoes splitting and cracking?
Usually this is as a result of irregular watering, sudden watering can split the skins particularly of thin-skinned varieties. Try to ensure the soil is always moist but not waterlogged.
why are my tomatoes not turning red?
Tomatoes need plenty of sun to ripen and turn red, so if they are in a pot ensure they are in the brightest spot possible. Some varieties are designed to be yellow, orange, green or even black so make sure you label all your plants so that you know what to expect!
why are my tomato plants wilting?
If a mature plant is wilting it is usually a sign of drought – so water well, especially during hot weather especially if it is in a pot or grow bag. Occasionally something might have damaged the root. Young plants can be susceptible to sciarid fly or damping off, both of which damage the roots and cause wilt. Plants may also show signs of wilting if they are sitting in waterlogged soil.
why are my tomato plants turning yellow?
Yellow leaves are a sure sign of a hungry plant and can be a sign of magnesium deficiency. Once they are fruiting tomatoes need a weekly drink of a high potash liquid feed – seaweed fertiliser is ideal.
why are my tomato plants not flowering?
Usually this is a sign of a plant being too well fed with a fertilizer high in nitrogen, so do not start any liquid feeding until the plant is already in flower.
why are my tomato plants dying?
This could be the result of any of the above problems, or if you are particularly unlucky, a combination of them all!
why do tomato plants leaves curl?
There is a virus that causes tomato leaf curl, but that is unlikely in our temperate climate. The most likely cause in a greenhouse or polytunnel is overheating - the leaf is curling up to prevent further moisture loss.
Another more serious cause is herbicide contamination either in manure or compost, so make sure that it has come from a reliable (preferably organic) source.
why do my tomatoes have black bottoms?
This is usually caused by blossom end rot, the result of poor calcium take-up of the plant caused by irregular watering.
what is eating my tomato plants?
Not many animals will eat tomato plants as the leaves are toxic like their close relations, the potato. However, there is a caterpillar, the larva of the tomato moth, that is partial to the young leaves. They are masters of disguise so look underneath the leaves and squash the culprits.
why are my tomato seeds not germinating?
Tomato seeds are usually very quick to germinate (between one and two weeks), given warmth and moisture. It might be that the seeds are old, generally the fresher the better with tomatoes.
why are my tomatoes tasteless?
Some varieties have been grown for yield rather than flavour, so choose your varieties carefully. The most likely cause is lack of sunlight, however, which is what brings out the sugars in the fruit. If they’re in a pot move to a sunnier spot, feed with a high potash fertilizer and keep the soil moist.
why are my tomatoes hard?
If your tomatoes are ripe but have a hard core this could well be caused by temperature fluctuations – cold nights being the main cause.
why are my tomatoes mushy?
You might well be giving them too much water – try cutting back on the watering and see if that helps.
why are my tomatoes dry inside?
This can be caused by insufficient feeding. Make sure they get a weekly liquid feed of a high potash fertiliser.
frequently asked questions
how tall do tomato plants grow?
This does depend on the variety, but if you keep pinching out the side shoots of cordons (also known as indeterminate which is a clue) they will keep on going up until you tell them to stop by pinching out the growing shoot. There is no point in having them so tall that you cannot reach to pick the fruit, so 2 metres is usually the maximum.
where did tomatoes originate?
Tomatoes, like potatoes their close relation, come from South America and were not introduced to Europe until the end of the 16th Century. When they first arrived they were thought to be an aphrodisiac, hence their common name back in the day of “Love Apple”.
how many tomato plants per pot?
A mature tomato plant needs plenty of elbow room, so unless you have a very large pot they are best planted singly. You can fit 2 into a growbag, as the ideal spacing is 60-90cm apart.
are tomato plants perennial?
In their native environment of South America they are indeed perennial, but here we would treat them as an annual as our seasons are too variable for them to survive year round.
are tomato plants poisonous to dogs and cats?
The leaves are poisonous and foul tasting, so no dog or cat with any sense will touch them.
do tomato plants flower?
Yes, without their yellow flowers there would be no tomatoes for you to enjoy. One follows the other, as long as there are insects to sort out the pollination.
do tomato plants need a lot of water?
Yes, regular watering is very important for tomatoes if you want a high yield of juicy fruit. Overwatering can also cause problems, so only water when the pot begins to feel light, the soil feels dry or when the leaves begin to wilt slightly. This can be daily in a warm polytunnel or greenhouse.
can tomato plants survive winter?
Tomato plants rarely survive a British winter as the temperature is too cold, light levels are too low and we have bred them to exhaust themselves with heavy fruiting throughout the summer.
do tomato plants like coffee grounds?
Coffee grounds can be quite acidic, so best used with caution. They can help deter slugs if they are attacking your fruit, so a ring of grounds around the stem can help. They are best added into your compost heap to rot down amongst all the other kitchen and garden waste and create a nice friable mulch.
should I pick green tomatoes?
If the summer is coming to an end it is best to pick the green tomatoes and bring them indoors to ripen on a sunny windowsill. If you have a real glut you can turn them into a delicious chutney, or there are some Mexican recipes for green tomato sauce that are worth trying.
should I soak tomato seeds before planting?
There is no need to soak tomato seeds.
will tomato plants grow indoors?
Tomatoes need lots of sunlight so a polytunnel or greenhouse is best to ensure you get healthy plants and well ripened fruit. You can certainly germinate and grow the seedlings on a sunny windowsill, but once they start to flower they will need more sun than our own houses can provide. Some varieties like “Tumbling Tom” are small enough for a window box or hanging basket.
will store bought tomato seeds grow?
During the Covid crisis in 2020 when seeds were in short supply people managed to germinate new plants from the seeds in a slice of shop bought tomato. You can also dry off the seeds from a ripe tomato and store them to sow the following spring. It definitely works, but you might find many shop bought tomatoes have been bred for commercial production, so your own garden might not be quite what they have come to expect!
what to grow with tomatoes
Basil grows well as a ground cover plant under tomatoes, as well as tastes brilliant alongside it in a salad. Chives garlic and marigolds are good to deter aphid damage.
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