Living in a box

High visibility

The advantage of container growing is that you can have a lot of colour near the house and will see plants that might otherwise be lost in the garden. On a balcony you ideally want the lower plants, such as thyme, in pots at the front and taller ones at the back, so you'll need to consider this when buying pots.

Pot it up

Think about planting in more unusual containers, such as chimney pots, which can be made into a display with the tall chimney in the middle and smaller plants around it. When plants are put into groups like this they look more natural. The great thing about container gardening is that you can move the plants around to reflect your mood, or to suit the way they are looking during the year.

Beat the bulge

Make sure that your pot is U- shaped and doesn't bulge in the middle - like a goldfish bowl - or it will be extremely difficult to pot things on without chopping at the plant and roots or even breaking the pot.

Evergreen

Use evergreen plants and shrubs where possible on a balcony or patio so that you won't have to spend time pulling out dead plants and putting in new ones to achieve a year-round display (see box for suitable evergreen plants). The other reason to have evergreens is that because balconies are usually attached to apartments there will be very little storage space in the home in which to overwinter bulbs and so on. So the plants on the balcony or window box should be able to be there all the time. You can then add annuals for extra colour.

Mixed textures

For colour interest with evergreens, choose leaves with different green and gold or white variegation. In a small space you'll get more of a rounded garden if you opt for lots of different textures, choosing plants with furry, prickly, silky, round and long leaves. Walk around a garden centre looking at all the different textures and find ones that mix well together.

Perfect conditions

The advantage of planting in pots is that you can create the perfect soil conditions and move the plants into the right areas. So many people ask me why their plant isn't thriving - I'm often amazed when I see the plant as it'll be growing in the wrong conditions. It's crucial to put shade-loving and sun-loving plants in the right place.

Keep it low

In window boxes you need low-growing plants as their positioning high up means that they are subjected to a good deal of wind. Campanulas are good and you can even get evergreen ones now. Or try London Pride and polyanthus. Rockery plants are also a good, low-growing option.

Size matters

Read the label very carefully and it will tell you whether you need acid soil, sun or shade and, crucially, how tall the plant will eventually grow (this determines the pot size). Sadly, plant labels aren't nearly as informative as they used to be and some of them aren't even correct. If you treat a plant well it may grow much taller than the label says and vice versa. You can get almost any plant you want in any size nowadays - so if you like a plant, tour garden centres until you find one the size you need.

Well fed

Container plants do need a good feed once a month because once they've used up all the nutrients, they're left with nothing. Phostrogen is good and not too expensive and acid loving plants will need an iron tonic.

On the dry

The main difficulty with container planting is keeping everything watered. Small pots, especially, dry out very quickly. With smaller pots you gradually learn how much water they are holding by picking them up - you can tell when they're too dry. It's very difficult to make sure they stay watered when you're away and you really need a friend or neighbour to water them for you, otherwise you'll have to practically drown them before you go, sit them in a basin, or try and make sure that any rain that falls will reach them. In summer they should be watered once a day, preferably in the evening.

High maintenance

If you grow annuals in a window-box you should throw out the soil (preferably onto a compost heap) after the plants have died back because the goodness will have left the soil. Dead-head all flowers as they die back, especially roses, to get as many flowers as possible. Container-grown plants can be pruned to suit the space, for instance, you can make plants grow out sideways rather than backwards into the plant behind it. Always prune the plants after they've flowered, feed them and pot them on, if necessary, so that they produce a strong crop the following season.

Jill Scott runs courses in gardening. Tel: 048 663 41308