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Organic Gardening:

How to grow organic Tomatoes

Tomatoes come in a bewildering variety of shapes and colours

Tomatoes

Lycopersicon esculentum

Family: Solanaceae (Group 8)

You can grow organic tomatoes. It's easier than you think - and the difference in the taste is simply astounding. Not only that, but you're not limited to the supermarket offering (small or medium). Tomatoes come in numerous different shapes, sizes and colours. Get hold of a specialist tomato catalogue and you will find pages and pages of different types, something for everyone, and for any purpose you can imagine. And you can get varieties to grow outdoors or under glass.

Cordon or Indeterminate types

Cordon tomatoes must be provided with support and the side shoots need to be removed regularly to channel production into fruiting. Once the plant has reached the top of the support (up to about 120cm (4')), or when 4 trusses of fruit have set, the main growing point is pinched out. Due to the short growing season in the UK, it is unlikely that more than 4 trusses will reach maturity in this country, at least for the time being. Who knows what global warming may bring?

Bush or Determinate types

Somewhat sprawling, bushy plants which can be grown without supports (or so they say, although the ones I tried fell over, so I had to give them a stick each, anyway - the sticks can be shorter, though, so you may be able to use fleece). As fruits are often produced close to the ground on these plants (basically, the whole plant is close to the ground), straw or plastic mulches (particularly black and white plastic, black side down) are useful to keep fruit clean. Note that access to insect pollinators is necessary once flowering has started - meaning you have to take the fleece off.

Recommended cultivars

Outdoor Cordon
Gardener's Delight	Cherry	Excellent flavour, Also for cold greenhouse
Sweet 100	Cherry	Also for cold greenhouse
Outdoor Girl	Standard	Early, good in cool years
Gemini	Standard	Good for cool summers
Outdoor Bush
Red Alert F1	Standard	Early, good flavour
Roma	Plum	May need support
Greenhouse (all cordons)
Alicante	Standard	Reliable, heavy cropper, Resistant to greenback
Dombito	Beefsteak	Good disease resistance
Golden Sunrise	Standard yellow	Tasty and juicy
Tigerella	Standard striped	Early, yields well
Cherry Belle F1	Cherry	Outstanding flavour

Dwarf varieties

These are miniature bush types, sometimes no more than 20cm (8") tall, low yielding, and mainly used in pots. There are also miniature trailing types, such as Tumbler, which are often grown in hanging baskets.

Fruit types

Apart from the standard red tomato found in every supermarket, there are also pink, orange, yellow and striped tomatoes. Sizes range from the smallest 'currant', through cherry, small, large and beefsteak. These last are very large, and of a more uneven shape more like a capsicum, good for stuffing, with thick walls.

As well as variations in size and colour, there are also several different shapes available; in addition to the usual round tomato and the chunky beefsteak types, there are also plum tomatoes (used extensively in Italian cooking), the Oxheart and more recently, pear-shaped types.

Cultivation methods - outdoors

As a general rule, tomatoes can only be grown successfully outdoors in the Southern half of the British Isles, although use of the fluid sowing method combined with black and white plastic mulch and perforated or fleecy films may produce a crop even as far north as Edinburgh, I am told. They can also be grown in containers, which can be brought outside for the warmer months and returned to the greenhouse when the weather turns against you (presuming you haven't tied the supports to the greenhouse framework so irrevocably that you can't get it off without damaging the plant!).

Site and soil

Tomatoes grow best on a sheltered site, ideally backed by a South-facing wall. If the site is exposed, erect an artificial windbreak. The soil should be fertile, well-drained, and moisture retentive. If the soil is at all acid, it should be limed. Work in plenty of well-rotted compost or manure before planting out, plus 125gm/sq metre (4oz/sq yard) of fish, blood and bone and 125gm/sq metre (4oz/sq yard) of rock potash. If growing tomatoes in containers, use a John Innes number 3 or equivalent.

Tomatoes should be kept as far away from potatoes as possible, because they share almost all the same pests and diseases. Tomatoes should be included in a rotation with the other Solanaceae (potatoes, aubergines/eggplants, peppers and chillis are all Solanaceae).

Sowing

Sow the seed no more than 8 weeks before the last expected frost date for your area. Good quality tomato seed should be sown indoors at a minimum temperature of 60ªF (16ªC). Sow the seeds individually 20-25mm (¾-1") deep in trays or modules. As they germinate and reach a size when they can be handled, transplant them into 10cm (3½") pots. At 6 weeks, start hardening the plants off, aiming to plant them out at 8 weeks once the soil temperatures have reached 50ªC (10ªC), and the plants are beginning to flower. If the weather forecast is for frost, delay planting until the weather improves.

Spacing

Cordons 40-50cm (15-18") each way, Bushes 50-60cm (18-24") each way, Dwarfs 25-30cm (10-12") each way. Cordons can also be grown in large containers about the size of a standard bucket (one per container) or two or three to a growbag. If you are using growbags, you will need to find some way to support the cane, as there is insufficient depth of soil to hold it steady. This is fine, if you are placing the bag onto the ground - just push the cane straight through the plastic into the ground, but if you are growing them on the patio, there may be a problem. To be perfectly honest, you are better off putting the soil from the growbag into a couple of buckets (make sure there are drainage holes in the bottom) and planting your tomatoes in there. This way, the soil doesn't dry out so fast, so it's easier to keep them moist. Adding a few water crystals helps, too.

Mulching, support and crop protection

Mulch is optional. Use either black plastic mulch or black and white (white side up to reflect the light back up onto the fruit). Cloches, fleece and perforated film can all be used until the plants are in flower, when access must be provided for pollination. Cloches can be stood on end "wrapped round" the plant. Fleeces and films must be gradually cut away above the plants, but left in place on either side to give additional shelter.

Cordon varieties need to be tied to 2m (6') canes (the bottom 30-40cm (foot or so) of which is pushed into the soil) at planting out, or to two or three parallel wires run between stakes. The main stem must be tied about every 30cm (foot) as it grows, and sideshoots which develop in the leaf axils need to be removed regularly (at least twice a week).

After 4-5 trusses of fruit have set (3 in the North), or when the leader reaches the top of the stake, in late July or early August, pinch out the growing point, a couple of leaves above the top truss.

Watering

Once plants are established, watering should not be needed until flowering starts except for container-grown plants and those in growbags. After this, apply about 10 litres per square metre (2 gals/sq yard) every week. The soil must not be allowed to dry out, or blossom-end rot will almost certainly develop. Growbags and containers will probably need watering every evening.

Feeding

Plants grown in the open ground should need little feeding if the soil was properly prepared. Container-grown plants will need to be fed regularly, every watering or every other watering, with tomato fertiliser or comfrey liquid. Both of these feeds are high in potash, which aids fruit production without encouraging too much leafy growth.

Harvest

Unprotected outdoor tomatoes are normally ready from about mid-August. Pick fruit as ripe as possible for the best flavour. Try one straight off the plant: who needs salad dressing?

In late September, mulch outdoor cordons with straw, cut them down and cover with cloches to assist the fruit to ripen. Bush cultivars can also be cloched, and container-grown plants moved under cover, if you can move them at all.

If frost threatens before the fruit ripens, there are 4 options available:

Pull up plants and hang by their roots in a greenhouse or somewhere warm indoors (i.e. not a cellar);
Cut trusses with about 10cm (4") of stem and hang between 2 horizontal canes to ripen indoors or in a greenhouse;
Pick fruits individually, wrap loosely in paper and store in a cool place - ripen small quantities as required in a warm place in the dark, placing a banana into the container with them, which will produce ethylene gas to encourage ripening;
Use remaining fruit for chutney.

New methods for early outdoor crops

Developed by research stations for bush tomatoes, the fluid sowing methods avoid the need to raise plants indoors in heat. They have been used successfully in the Midlands, and South of England and Wales, and as far North as Edinburgh.

In Northern and cold areas, sow 7-10 days later than stated.

Fluid sowing in a frame
- Keep frame covered to warm up for two weeks
- Sow pre-germinated seeds in late March/early April
- Sow 25mm (1") deep in rows 12cm (5") apart, thin to 10cm (4") between plants in the rows
- Protect frames with sacking if frost threatens
- Ventilate well on sunny days
- Plant out mid to late May at 15-20cm (6-8") high after hardening off in the normal way
Fluid sowing in situ
- Warm up soil with cloches or clear plastic film
- Sow pre-germinated seed about the third week of April
- Station sow 50-60cm (18-24") apart each way
- If covered with cloches until flowering, sowings can be made 2 weeks earlier in the South and 1 week earlier in the Midlands, East Anglia etc.
Using fleece and perforated film

Low polytunnels are not very successful for bush tomatoes, due to high humidity, although there are newer ventilated types that may be a partial solution to this problem. However, use of fleece or perforated plastic film will result in heavier crops. This can either be used as a tunnel cloche or a floating mulch.

Once flowers can be seen, around mid-June, start making intermittent cuts about 1m (3') long in the centre of the film. A week later, cut the remaining gaps, but leave the cover on either side to give shelter. This method can be combined with fluid sowing and planting through plastic mulch.

Pests, diseases and disorders

Outdoor tomatoes suffer from few pests. The main ones are: Potato cyst eelworm, which can be controlled by rotation, not using the site for any Solanaceae for 6 years to starve out the life cycle; Greenfly and whitefly, which can be controlled with derris or fatty acid sprays.
Magnesium deficiency causes yellowing of leaves between the veins, from the bottom of the plant upwards. The best way to avoid it is by ensuring the soil is sufficiently fed before planting. On acid soils, the preferred liming agent is dolomitic rock, which contains magnesium. A top dressing of wood ash may alleviate the problem.
Potassium deficiency may cause blotchy ripening, hollow fruit and greenback, mainly in protected crops. Feeding regularly with comfrey liquid or tomato fertiliser will prevent the problem.
Allowing soil to dry out may cause blossom end rot or fruit splitting. The use of plastic mulches will help to keep the soil moist in hot, dry conditions.
In wet seasons, potato blight can be very serious. Spray fortnightly with Bordeaux mixture as soon as symptoms appear. Keep potato and tomato plants as far apart as possible. Rotate crops.
Botrytis mainly affects overcrowded plantings, infecting damaged areas of stem with a grey mould. Remove infected parts and dust with sulphur. Practise good hygeine, e.g. wash hands after handling plants which you suspect may be infected.

If you're interested in healthy food, you may also be interested in our sister site, The Health Site, Your Online Health Channel.

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