Gardening: Plot your pots

A random scattering of plants in pots can look as chaotic as a bag of liquorice all-sorts. Sarah Raven advises on evergreens and flowers and gives some tips on how to achieve strong, healthy growth and a long- flowering season

THE KEY to success with pots is lots. A single pot has negligible impact, whereas a pair flanking a doorway or a collection of five or more can transform a whole area of your garden.

But pink, blue, yellow and white flowers, all crammed together in a mixture of shiny ceramic, plain terracotta and glazed pots will look as chaotic as a bag of liquorice all-sorts. You want more style than that. A linking element will give you an ordered beauty, a structure and rhythm, like a formal garden in miniature. Line up identical pots and plant them all with the same flower, or go for a kind of coherent diversity, using various sizes of the same shaped pot, or different flowers in the same colour.

Play around with the idea so that it doesn't look too stuffy. Single rows of clipped box (Buxus sempervirens) look wonderful in elegant long Tom pots arranged at 1-2m (3-7ft) intervals down a path. Box looks as good covered in frost or snow as it does in spring, when the new growth glows acid-green. Since it doesn't need much light, it will even grow in a relatively dark backyard.

Santolina (Santolina chamaecyparissus) is another excellent evergreen for pots. Its bright silvery domes of foliage are easy to keep neat and clipped. A row of pots set on outdoor steps will contrast well with brick and shine out against stone or concrete. Santolina is also one of the easiest things to propagate. The plants grow quickly and will form neat domes in a matter of months. Like box, it will look good all winter. Cut it back to a neat, rounded shape in late spring and it will go on looking good for years.

Evergreens are all very well, but you want some flowery abundance and brilliant colour in the garden too. Half-hardy annuals will soon grow safely outside, so now is the time to visit the garden centre. But don't get carried away. Buy trays of one colour, not the multicoloured collections.

Petunias, especially the trailing Surfinia Series, and pelargoniums thrive with little water. They also flower for twice as long in pots as nicotianas or antirrhinums. Go for a rich velvety purple or magenta petunia, rather than a pale pink or apricot, and avoid any with stripes - you will have tired of them by the end of the summer.

Alternate pots of pelargoniums in a bright, searing pink such as 'Orchid Paloma' with a rich, dark crimson such as 'Tomcat', 'Lord Bute' or 'Stadt Bern'. If you want a real froth, go for a double pale pink such as 'Deacon Minuet' next to a white 'Deacon Arlon'. All four will give you strong, healthy green foliage and rampant growth. The flowers last for at least four or five months at a stretch.

That's enough on style. How do you ensure that your pot plants are healthy and strong? Fill the pots with a 50/50 mix of a loam-based compost (John Innes Number Two is rich in nutrients and good at retaining moisture), and a cheaper multi-purpose potting compost with a light airy consistency which is good for roots.

Good brands such as Levington's also incorporate water-retaining granules in their compost. If you are planting into terracotta, which will rapidly lose water through evaporation on a hot day, you should add some extra water-retaining granules, mixing them thoroughly into the compost.

Don't just fill the pots up and then add the granules to the top 8-10cm (3-4in) of compost. If you do, there will be more water in this layer. This encourages roots to form near the surface, where they are vulnerable to heat and can get baked by the sun.

Place the pots on generous trays or saucers. In the heat of summer these should be filled up morning and night. For bumper-sized plants, which should last all through the summer and into the autumn, give the plants a liquid seaweed feed every two or three weeks.

The more you dead-head these plants, the more they will produce. Just pull off the flower heads of petunias as they fade. Old pelargonium flowers should be removed at the base of the stalk. If you let them set seed, you will reduce the quantity and quality of flowers in subsequent years. Healthy pelargoniums can be over-wintered for planting out the following year. Cut them right back when you bring them under cover and keep them cool and fairly dry. They will lie dormant through the winter, and start growing again in the early spring.

Mail-order pelargoniums: Fibrex Nurseries Ltd (01789 720788). Unusual zonal pelargoniums: Kent Street Nurseries, Sedlescombe, Battle, East Sussex (01424 751134). Long Tom pots: Gopsall Pottery,Winchelsea Beach, East Sussex (01797 222770)