Pots of production

Many vegetables will give a good harvest when grown in containers. They can look just as attractive as ornamental plants and make the most of a small space. Gardeners with only patios or balconies can still get a taste of fresh home-grown crops, while newcomers to vegetable growing may find containers less daunting than a garden plot. So says Sue Stickland

Pots, troughs and window boxes are often filled with summer bedding, but they could equally easily be used to grow vegetables. A surprising range of crops will grow well in containers of all sorts, and many look attractive too, with handsome foliage and colourful fruit. They can turn paved yards and patios into productive spaces, and can also be an answer where garden soil is poor, or otherwise unsuitable for growing crops.

Although regular watering and feeding are essential, growing vegetables in containers is not difficult. In fact, it is sometimes simpler than planting them out on a plot - there is no digging, for example, and it can be easier to control pests such as slugs. Yields may not be as high as for crops in the ground, but the satisfaction and convenience of harvesting fresh produce from your doorstep can more than compensate for this.

The basics

Almost any container can be used – from ordinary growing-bags and plastic pots to ornate urns and old sinks. Purpose-made containers are sold for some crops, particularly potatoes. The main problem is keeping plants moist, while at the same time avoiding waterlogging. Make sure improvised containers have adequate drainage holes, and line the sides of terracotta pots with plastic to help stop them drying out.

The larger the containers, the easier it will be to get the watering and feeding right, and the better the crops. However, if you want to move them around, bear in mind their weight. As a rough guide, most vegetables will produce a worthwhile yield from a 25cm (10inch) diameter (10-litre) pot or its equivalent; larger containers will accommodate the more vigorous plants, or a mix of crops. Avoid shallow containers less than 15cm (6in) deep.

The most convenient growing medium to use is a multi-purpose, potting or container compost. Mixing about 25 percent of good garden soil into a soil-less media can help supply nutrients and save on costs, but will increase the weight. Incorporating garden compost can be valuable, particularly in large containers; just be aware of weed seeds and the possibility of pests.

Most vegetable crops will need a fairly sunny sheltered spot, especially early in the year, but in midsummer some will do as well (or even better) in semi-shade – particularly salads and leafy vegetables. One great advantage of growing in containers is that they can be moved around to suit the season and the crop.

Watering is the main task, it will be necessary at least once a day in hot, dry weather, so it is important to site containers where there is easy access to a tap or water butt. Alternatively, an automatic watering system can be set up. Help drainage by raising containers off hard surfaces using tiles or ‘pot feet’.

Salads and leaf crops

Image right: Baby leaf salads give useful pickings even from small pots - beetroot ‘Bull’s Blood’ (used for its deep purple leaves), pak choi, mizuna, and mustard ‘Red Frills’. The oriental greens will quickly bolt in spring and summer, but the advantage of growing each in a separate pot is that as one crop goes past its best, it can easily be replaced. A useful guide for a constant supply of most spring and summer salad leaves is to make another sowing as soon as the first is just ready to harvest.

Leafy salads make quick and easy container crops almost all year round. They are undemanding, and will grow in small pots or window boxes; follow on from tomatoes in a growing-bag; or fill gaps when large containers are planted up with other crops. Lettuce can be grown throughout the summer, with rocket and Oriental greens in the cooler months, and crops such as hardy chicories and landcress in winter.

The quickest harvests and best yields are obtained by growing salads as ‘baby leaf’ crops. Sow seed evenly and thinly over the surface of the container, cover with a sprinkling of compost and water well. Aim for plants about 2cm (0.75in) apart each way, and start picking leaves when they are 10cm (4in) high. Seed mixtures such as an ‘Oriental mix’ or ‘lettuce mix’ give a range of cultivars from one packet and are ideal for small spaces. Alternatively, for hearted lettuces, use small-headed cultivars such as ‘Little Gem’ (mini-cos) or ‘Mini-green’ (iceberg).

Regular sowings will be needed for a continuous supply. Start the earliest in March in pots in a light warm spot, but move to semi-shade for midsummer sowings. Keep plants continually moist. If growth is poor, feed regularly with a general-purpose liquid fertiliser once the harvest has begun.

Some leafy vegetables are valuable too, particularly leaf beets and chards. One sowing in April will give attractive plants that can be harvested all summer and into autumn. Sow seeds direct into the containers, or into modules for planting out about 7.5cm (3in) apart each way. Keep picking the young leaves. After the first harvest, feed weekly with a general-purpose liquid feed.

Image right: Cultivars of chard with coloured stems and midribs give a colourful display, and make productive container crops. They include Swiss chards such as ‘Red Ribbed’ and ‘Ruby Red’, yellow-stemmed cultivars such as ‘Bright Yellow’, and ‘Bright Lights’ (‘rainbow chard’) - a mixture of reds, oranges, yellows and white. Sow anytime from April to late July. For the best return, space plants closely together in 10-litre pots (or their equivalent) and harvest young leaves regularly until mid- to late autumn.

For autumn and early spring leaves, kales such as ‘Red Russian’ or ‘Black Tuscany’ or curly ‘Redbor’ make handsome and useful crops. Raise plants in modules from May or June sowings and plant 15-20cm (6-8in) apart. Although kales grow tall on a vegetable plot, close spacing in a container will keep them shorter and more compact.

Fruiting crops

Tender fruiting crops such as tomatoes, cucumbers and courgettes appreciate the warmth created by walls and paving, making them good candidates for growing in large containers or growing-bags in a sunny spot. Peppers, chillies and aubergines can also be successful in warmer areas of the UK. Looked after well, they should fruit for several months during summer and early autumn.

Cultivars described as ‘patio’ selections are usually compact plants, often with smaller fruit. Other cultivars will still grow well, but may need staking or pinching out to keep them neat, and large-fruited cultivars may only produce relatively small numbers of fruits.

Plants can either be raised from seed in a greenhouse/windowsill early in the year, or bought from garden centres or catalogues in May or early June, for planting once the threat of frost is past. Cover young plants with fleece on cold nights to give them some protection.

The mature plants can be demanding – they will need daily or twice-daily watering in hot weather, and feeding regularly with tomato liquid feed once the flowers and fruit form. Mulching the surface of the container with bark or gravel can help to conserve moisture.

Image left: Cucumbers will crop well in large containers. Small-fruited cultivars are the best for giving a continual supply of fruit. The smooth-skinned ‘Diva’ or a rougher skinned ridge cultivar or gherkin will do well in a sunny spot in most areas – the fruit are deliciously crunchy fresh in salads as well as pickled. Allow one plant per 20-litre pot (or its equivalent). Plants can be left to trail, but look more attractive if trained up a wigwam of canes; tie in the main shoots as they grow and pinch out sideshoots beyond the first embryo fruit. In warmer areas, mini all-female cultivars such as ‘Rocky’ or ‘Cucino’ may grow outdoors in a sheltered spot.

Image right: Bush tomatoes need no staking or pinching out – they will trail decoratively over the sides of the container, keeping the fruit clean. Put one plant per 10-15-litre pot (or its equivalent) – the larger the pot, the easier it will be to keep it watered. If plants dry out, flowers may fail to set and fruit can split or develop the physiological condition blossom end rot.

Image left: Aubergines make good container plants for warmer areas, and those with exotic stripy, white, or finger-shaped fruit can be a real talking point. Cultivars above are ‘Ping Tung Long’ (elongated purple fruits), ‘Fairy Tale’ and ‘Listada de Gandia’ (stripey). Small-fruited cultivars usually give the greatest number of fruits and often higher yields. These will grow well in 10-litre pots (or their equivalent) and generally need little support. For round purple fruits try ‘Ophelia’ and for white fruits ‘Mohican’.

Image right: Chilli plants give excellent value for space – their healthy foliage and colourful fruit provide an attractive display over a long period, and just one or two plants in a patio pot can make you self-sufficient. Keep the pots in a warm, sheltered spot. Taller cultivars do best in 10-litre pots (or equivalent) and may need staking, but compact cultivars such as ‘Apache’ and ‘Prairie Fire’ form bushy spreading plants and will grow even in small pots.

Peas and beans

Peas and beans give relatively low yields in containers, but added value comes from their attractive flowers and pods. Use at least a 10-litre pot, and keep plants well watered or the flowers will not set.

Dwarf sugar (mangetout) peas such as ‘Norli’ do well early in the year, giving young shoots and tendrils for salads as well as a harvest of pods. Dib in seeds in March to May about 5cm (2in) apart, equally distributed over surface of the container. Provide wigwam of canes and string or twiggy sticks for them to climb up.

Dwarf French beans can also give a worthwhile harvest and cultivars with coloured pods such as ‘Purple Teepee’ and ‘Golden Teepee’ are particularly decorative. Make two sowings direct into containers in May and June for a July to September harvest. Space plants about 10cm (4in) apart each way. Runner beans are more demanding plants and flower set is less reliable, although they give a wonderful show of flowers. Dwarf cultivars, such as 'Hestia', which have short pods, are the most suitable.

Root vegetables

Quick-growing root vegetables such as early carrots, beetroot and turnips make productive container crops. Spaced closely and pulled when small, they are sweet and tender, and can give good yields. As a bonus, a few of their small tender leaves can also be picked for salads. Successional sowings can give harvests from mid-summer to mid-autumn.

Carrots can be easier to grow in containers than they are in the ground, and their bright green feathery foliage is good foil for other plants. A 25cm (10in) (10-litre) pot or its equivalent can yield at least a kilogram of roots.

Short early cultivars of carrot are the most suitable – there are many new ones, but the traditional ‘Amsterdam Forcing 3 – Minicor’ and ‘Nantes Early’ still do well. Round cultivars such as ‘Parmex’ are recommended for shallow containers. Beetroot cultivars such as ‘Moulin Rouge’ are selected as patio or ‘baby’ beets because they develop particularly good colour and shape when young, but it is worth trying any globe cultivar.

Carrots and beetroot can be sown anytime from mid-March to June. Two or three sowings are needed for a continual supply. Scatter the seeds thinly and evenly over the surface of the container and cover with a sprinkling of multi-purpose compost. Wide spacings will give fewer larger roots more quickly, and close spacings lots of tiny ones – a compromise usually gives the best overall yield. Aim for seedlings 3-4cm (1.25-1.5in) apart for carrots and 4-5cm (1.5-2in) for beetroot, to give edible roots in about 12 weeks. The containers will need regular watering to keep the roots moist, otherwise they may split, but feeding should probably not be necessary.

Turnips can give an even quicker harvest. They are easiest to grow early and late in the season - in summer, they quickly bolt. Sow in March and July/August for succulent baby roots in as little as eight weeks.

Spring onions, ‘mini’ bulb onions and shallots also make worthwhile container crops. Shallots can be expensive to buy in the shops, but are easy to grow in a large container. Alternatively, grow them individually in 15cm (6in) pots. Most cultivars do well if sets are planted in mid-March (sooner in milder area). Push them into the compost so that their tips are just protruding from the soil, spacing them about 15-20cm (6-8in) apart each way. They soon produce vigorous clumps of healthy green leaves – a few could be snipped off for use in salads without harming the crop. Feed with a general-purpose liquid feed until the bulbs start to form in June. When the tops bend and yellow, lift and dry the crop for storage.

Potatoes

Potatoes are a very easy container crop, although the way they are harvested means that they should be grown in a pot on their own rather than mixed with other crops.

As a rough guide, allow one seed tuber per 20-litre pot – this should give an edible return of roughly 1-1.5kg (2-3lb). In mid- to late spring, half fill the pot with compost and bury the seed potato just below the surface. As shoots grow, cover them with more compost until the pot is almost full.

Water regularly and feed with a general-purpose or tomato feed after six to eight weeks.

By mid-summer potatoes should be ready for eating – either feel for tubers and remove those of edible size, leaving the plant to grow on, or tip out the pot and harvest the lot.

Early cultivars are the best choice, producing good yields in early summer without too much sprawling top growth. ‘Dunluce’, ‘Orla’ and ‘Lady Christl’, for example, have compact plants and a good flavour. Alternatively try ‘baby’ earlies such as ‘Mimi’, bred to produce lots of tiny tubers for cooking whole.

Sue Stickland is a gardener and writer with a special interest in vegetable growing