How To Sow & Grow Tomatoes

Tomatoes From Seed

If you're planning to grow tomatoes in a tunnel or greenhouse, sow your seeds in late February-March, which will give you nice plants ready to set out in April–May. If you're growing tomatoes outside, delay sowing until late March–April, which will give you plants for setting out from late May to mid-June.

Tomato seed is easy to germinate and grow on provided you practise good hygiene, use the freshest possible seed compost, and keep a careful eye on temperature, watering and light. Sow the seed thinly onto gently firmed trays or pots of compost – about ten seeds to a 3½" (9 cm) pot, or a couple of hundred seeds to a standard seed tray (you can divide up the tray to sow a number of varieties if you wish). Cover the seed with a layer of vermiculite or sieved fresh seed compost roughly as thick as the seeds themselves.

Water the trays or pots and stand them somewhere warm and in good light. A constant temperature of 64-77°F (18-25°C) is perfect, so if you have a heated propagator that is ideal; alternatively, a warm windowsill will be fine. Avoid putting the tray or pot in a plastic bag as this can create excessive humidity and the possibility of fungal problems. Keep the compost just moist but never soggy. At a temperature of 75°F (24°C) seeds should germinate within five to ten days; a cooler temperature will slow down germination, and below 50°F (10°C) the seeds will probably not germinate at all.

Once the seeds have germinated, keep a very close eye on them as the seedlings can turn leggy very quickly. Provide as much light as you possibly can and grow the seedlings on at a reduced temperature of around 65°F (18°C). If you are growing them on a windowsill or using a similar uni-directional light source you will need to turn the growing container several times a day to ensure that the seedlings do not grow towards the light.

Watering is also important – too much water and you will produce weak, leggy seedlings. It is better to let the compost all but dry out before watering again rather than keeping the compost at a 'steady moist'. Once the seedlings have produced their first true leaves (that is, the first set of leaves after the seedling leaves) prick out (transplant) your seedlings into modules or small pots. As with all seedlings, hold them by their leaves rather than their stems when pricking out. If the seedlings are a little leggy you can set them deeper to shorten the height of the seedling, as tomato seedlings will stem-root.

Growing On (for those purchasing our tomato plants – read from here on!)

Continue growing on the plants at a temperature of 65°F (18.5°C) or more and pot on as required, so that you end up with individual plants in 3½" (9 cm) pots, standing about 6–8" (5-20 cm) tall - perfect for setting out. If you are planning to grow the plants outside and the threat of frost has not subsided, or you're just plain not ready to plant them out into their final position, pot the tomatoes on again to avoid their growth being checked or plants becoming root-bound.

Planting Out

Tomatoes always do better when grown under protection rather than outside, because of the increased warmth and the greater control you have over watering. Both greenhouses and polytunnels are absolutely perfect for this. Whether growing inside or out, your options for final setting out are: grow-bags, pots or in the ground. Because of the risk of blight and one or two other nasties it is probably unwise to grow plants in the ground; if you have grown them in a container or grow-bag you can physically take the problem away with little or no chance of long-term soil infection.

Grow-bags are 'ok' but, like everything, they are made for a price (which is usually cheap); if they have been standing around for some time the nutrients will have been released and the compost grown stale. In our opinion, growing in containers is the best way and will give you the best results (and is how we grow our tomatoes). You can easily make your own compost to fill the tubs by mixing fresh grow-bag compost with 25% horticultural grit or vermiculite to provide all-important drainage and adding 4oz (110g) of garden lime per 50 litres of compost.

If growing in grow-bags set out three plants per bag; if growing in containers, a 15-litre pot [13"/33 cm diameter] will be fine for one plant whilst a 40-litre tub [(20"/50 cm diameter]) is suitable for two or three plants. Plant firmly and, if the plants are leggy, a little deeper than usual. Put in a cane straight away and water in well.

Training

Despite what many people think, tomato training is easy as long as you know what kind of tomato you are growing. Tomatoes can be divided into two groups – bush varieties (sometimes called 'determinate' as they eventually form a flower cluster at the terminal growing point, causing the plant to stop growing taller) or cordon varieties (sometimes known as 'indeterminate' as they never set terminal flower clusters, only lateral ones, and continue to grow indefinitely).

For bush varieties you simply need to tie in the plant to support it, and more or less leave it to its own devices. You can thin some of the leaf if you wish, to improve air circulation, and similarly prune back some of the growth to contain the overall size.

For cordon varieties the idea is a little different but just as easy. Simply allow the main stem of the plant (the vine) to grow up a cane, or a string tied to the roof overhead, tying in as required. As the plant grows, remove all the non-flowering side shoots that appear. If you are worried as to which is which, allow them to develop a little more so you are able to see the difference before removing. When the plant has produced sufficient side shoots of flowers/fruit (called trusses) you simply 'stop' the plant by removing the top growing point. How many trusses of fruit to allow will depend on the variety; generally speaking, around five trusses is ideal for normal-size tomato varieties; four or even three for large beef tomatoes, while with cherry and currant tomatoes you can allow six, seven, or even more. For the rest of the growing season you will need to keep an eye out that further side shoots do not appear and try to grow away, and similarly ensure that the vine stays 'stopped'.

(Note: It's worth wearing gloves when side-shooting, tying-in and generally handling tomato plants, otherwise your hands will become covered in a greenish powder that, when you then try to wash it off, goes bright yellow and stains everything, though it will wash off/out eventually!)

Watering/Feeding

Water your tomatoes on a cyclic basis; that is, giving them a good drink and then allowing them to virtually dry out before watering again, though never allow them to dry out to the point of wilting. Keeping plants constantly moist will mean they grow quicker but the growth will be weaker, so if in doubt keep tomato plants on the dry side.

Soon after planting the tomatoes into their final position start a feeding regime. Tomatoes are gross feeders but this does not mean you should go over the top! With the young plants, and before any flowers are showing, use a good, balanced liquid feed once a week, or alternatively twice a week at half strength. As soon as the first flowers appear switch over to a feed higher in potash (most tomato fertilisers are) and feed as per their recommendation, or experiment by diluting down further but using more regularly. Continue this throughout the summer. As soon as the first flowers start to show it's also a good idea to lime the plants by sprinkling about 2oz (55g)of lime around the base of each plant; this will certainly do no harm and usually reduces blossom end rot on the first fruits (see below).

Pollination

Pollination should be something you do not need to worry about as insects, any natural movement of the plants, or unnatural movement of the plants caused by you working on them, should be enough to transfer the pollen. If you do want to artificially pollinate, this is easy – simply grasp the plant by the main stem and give it a good shake! You can do this every few days when the plants are in flower if you wish but it is usually not necessary.

Pest and Diseases

Despite the fact tomatoes can suffer from all sorts of things, in practice they rarely do. However, common problems you may come across include:

Blossom End Rot

Not a rot at all! The end of the fruit appears flattened (and sometimes curves in on itself), goes brown and remains hard. Most commonly this affects the first fruits that set; there is no cure for fruit affected with this but its occurrence can be reduced. It is not a disease but a physiological condition brought on by a lack of calcium and/or an imbalance of potash. Ensuring the compost you plant into contains good amounts of lime, and liming at first flowering, reduces the chances of this drastically. Allowing plants to dry out to the point of wilting will also cause greater instances of this so take care with watering.

Greenback

Again, this is not a disease but a physiological condition, which causes the top of the fruit and some of the inner flesh to remain green and stay hard to the point of sometimes being inedible when raw. You will see this most often in bad summers as it is caused by low temperatures and low light levels, as well as by the plants being kept too wet. There is no cure for affected fruits, but it shouldn't stop you eating them. If the weather improves later fruits will be fine.

White Fly, Aphids and Red Spider Mite

All of these can affect tomatoes; if you suffer an infestation it is really down to you as to your preferred method of control. Here on the nursery we prefer to deter rather than cure, by regularly spraying with our BioFriend Plant Defence - a concentrated garlic and seaweed-based mixture which discourages the pests as well as strengthening the plants' natural resistance so they can ward off invaders. Additionally, it is important to avoid excessively high temperatures so make sure there is good ventilation and air flow.

Blight

Blight is a fungal infection spread by wind, rain and rain splash (dormant spores splashed up from the soil), and causes brown, spreading blotches on the leaves and stems, as well as brown patches of rot on the fruits – and the rapid death of the plant. Outdoor crops are more likely to be affected than those grown inside, though if you water regularly with stored water from a water butt you may bring the problem indoors. Good plant hygiene, care with watering (avoiding splashing the foliage) and care with where the water comes from will all reduce the chances of this problem occurring. Preventative regular spraying with a concentrated garlic solution will also reduce the chances of the problem taking hold as the high sulphur content of garlic acts as a natural fungicide. If your plants do become infected with blight you may be able to keep them going just about by spraying regularly with garlic or a copper-based fungicide, but it really is better to cut your losses, clear and burn everything, and start again the following year.

Watering (again) – Getting the Flavour into the Fruit

If you grow parsnips you should know that they taste better after a frost or two; this is because the frost converts the starches in them to sugars, and sugars = flavour! If you grow peas you should know that a constant level of moderate moisture will give the best flavour; this is because moisture stops the sugars turning to starch in peas, and sugars = flavour! With tomatoes, the flavour (sugars) in the fruit develops when the tomato plants start to dry out, so when some of the fruits on your plants start to show colour take extra care with the watering, and try to allow the plants to all but dry out before watering, though never allow to the point of wilting. On a side note this answers the age-old question as to why most supermarket tomatoes have no flavour: most supermarket tomatoes are grown hydroponically or using nutrient film technique, which means the plants are never short of water and so the sugars and flavour never build.

Harvesting

By growing your own you should be able to allow your tomatoes to fully ripen on the vine before harvesting. It will be pretty obvious when the tomatoes are perfectly ripe – they will be red (or yellow or purple ...) and just off firm, and if you get down close to them they will smell like tomatoes! Pick as and when you need them. If they start to get ahead of you you're not using enough! You can always use up an excess by making a basic sauce or puree and freezing it; the slightly over-ripe ones are perfect for this as they have more flavour (and the cooking will kill off any bacteria before freezing). You should never need to let a tomato go to waste!

As tomatoes need warmth and good light to ripen, ripening can be slow in a poor year. If this is the case, either be patient or pick off a few tomatoes and bring them into the warmth of the house to ripen. This is something you may need to do with outdoor-grown tomatoes but will probably not need to with those grown under protection.

As the autumn starts to draw near day length shortens and temperatures drop – and your remaining fruits will hang green on the vines, steadfastly refusing to ripen! At this point it is best to cut your losses, pick the remaining crop to either use for chutney or else bring into the warmth to ripen.

Clearing Up

Finally, never ever, ever compost your spent tomato vines - even if you haven't seen any signs of blight or disease. The only thing to do with old tomato vines is to burn them! The spent compost from your grow bags or tubs can go on the veg or fruit garden, but avoid where you plan to grow spuds next year. Here on the nursery we actually use the tubs for over-wintered salad crops and carrots and things like that, before emptying them on the veg garden in the spring, and then refilling them for the next crop of tomatoes.

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