An expert guide for growing shrubs in containers

Many of the most decorative shrubs can be grown in large pots or tubs to adorn your patio or terrace. Here's a quick guide to help you get started.

Shrubs that grow well in containers include the aucuba, camellia, clematis, deutzia, euonymus, fire thorn, flowering currant, forsythia, honeysuckle, hypericum, kerria, Oregon grape, prunus, spirea, tamarix, weigela, and wisteria.

• Not all shrubs respond well to container culture, however. In general avoid kinds with thick, fleshy roots. But in other plants, the fact that the roots are restricted may actually improve flowering.

A shrub expected to grow 1.2 to 1.5 metres (four to five feet) tall and about 1.2 metres (four feet) wide will need a tub at least 75 centimetres (29.5 inches) wide by 45 centimetres (18 inches) deep.

• If there are no drainage holes in the bottom, you can make them with a drill.

• Add lightweight material to the bottom of the container so it won't be too heavy to move.
• Add a layer of potting soil deep enough so that when the plant is placed on it the base of the stem will be slightly below the rim of the tub.
• You can mix your own soil from three parts compost-based potting soil mix to one part coarse sand. Add about 60 millilitres (four tablespoons) of blood-and-bonemeal mix per 35 litres (37 quarts).

• Make sure that the root ball is moist and the root system is good before setting the shrub in the container.
• Fill in around the shrub with more of the prepared planting mix.
• Firm it down well; then fill with more soil mix to 1.5 centimetres (three quarters of an inch) below the rim.
• Water thoroughly, let the water settle, and soak the soil again.

• Confined roots cannot seek out water, so you must bring it to them. Water well whenever the soil surface dries out.
• A year after planting — and again monthly or if the leaves seem small and discoloured or when growth is meagre — apply a compost tea or a liquid organic fertilizer.
• Shrubs that tend to grow large can be kept small and healthy by annual or biannual root pruning. In any case, maintaining a healthy shrub requires pruning both the top growth and the roots in fall or early spring every four to six years.
• Remove the shrub from its pot and strip about 10 centimetres (four inches) of roots and soil from the root ball.
• Scrub the container and repot with fresh soil mix.
• In cold areas, containers should be put in the ground each fall to prevent undue frost penetration, which could kill the plants, even within their recommended hardiness zone.

Container gardening is not restricted to small flowers. Keep this guide in mind and grow a healthy shrub in a convenient container today.