Which plants actually last for years in a pot?

Almost anything survives a season in a container. The question is what is still good in year five. Three things separate the plants that manage it: they do not mind their roots being confined, they are hardy enough that a pot's exposed rootball still survives winter, and they hold their shape rather than needing to be cut to the ground each year.

Step by step

1. Buy for hardiness two steps better than your garden needs.Compost in a pot can be several degrees colder than the ground, and it freezes right through. A plant rated as borderline hardy in your area will not survive in a container in a hard winter unless you protect it.
2. Prefer naturally slow and compact plants.Slow growth means fewer repottings, fewer feed problems and a plant that stays in proportion to its pot. Dwarf and compact cultivars exist for exactly this and are worth the extra cost.
3. Choose evergreens for the structure.A container in a prominent position is looked at every day of the year. Box, holly, bay, yew, pittosporum, skimmia, sarcococca, dwarf conifers and small-leaved hebes all earn their place in February as well as June.
4. Use the reliable performers.Bay and box for clipped shapes. Olive and pittosporum for a Mediterranean look. Japanese maple for a shaded, sheltered spot. Hydrangea for summer bulk. Camellia, pieris and skimmia for ericaceous shade. Agapanthus, which flowers better pot-bound. Phormium and dwarf pines for structure. Blueberries, which prefer a pot in most British gardens.
5. Recognise what will not do it.Anything with a deep taproot such as a mature birch or an oak. Anything vigorously suckering like sumac or bamboo without a very heavy container. Thirsty large-leaved plants like Fatsia in full sun. Most large-flowered clematis, which resent hot roots. And short-lived perennials that need dividing every two years anyway.
6. Match the pot to the plant's expected life.For a decade-long plant, buy the biggest frost-proof pot you can lift and use loam-based compost. Cheap thin plastic and multipurpose compost are the right choice for a season of bedding and the wrong one for a bay tree.
7. Commit to the maintenance the plant needs.Annual top-dressing, an annual feed, repotting or root pruning every three to five years, and winter drainage. A long-term container plant is a low-effort commitment but not a no-effort one.

Tips

• Agapanthus, clivia and some camellias flower better when slightly root restricted. Repotting them too generously produces leaves and no flowers.
• Grouping several pots together helps them all — mutual shelter from wind, less evaporation from the sides, and a better microclimate in winter.
• For anything ericaceous in a hard-water area, water with collected rainwater. Over years, tap water raises the pH of the compost and the plant slowly goes yellow.

Common mistakes

• Buying a large fast-growing shrub for a modest pot — It looks right for one season and is then permanently root-bound, wilting daily and needing a pot you cannot lift. Choose slow, or choose a bigger pot from the start.
• Treating a permanent container plant like bedding — Multipurpose compost, no top-dressing and liquid feed only will keep a shrub alive for two years and then it declines. Loam-based compost and an annual top-dress is what makes it a decade plant.
• Ignoring winter drainage on a plant that is otherwise well chosen — More established container plants die of winter wet than of any other cause. Pot feet, no saucer and shelter from persistent rain are what keep them going.

Questions people ask