Why dwarf conifers earn their place on the patio

A dwarf conifer in a decent pot does something no bedding plant can manage: it looks good in January. Slow-growing, evergreen and quietly architectural, these plants hold their shape through wind, frost and drizzle, giving a patio structure that bedding displays lose by Bonfire Night. Many will sit happily in a container for years, growing perhaps two to five centimetres a year rather than rocketing away.

The trick is understanding that a conifer in a pot is not a small shrub in the ground. Its roots have a fraction of the soil volume, the compost dries out faster, and cold winter winds pull moisture from the needles with no thawed roots to replace it. Get compost, drainage, watering and repotting right, and a dwarf conifer will thrive on a patio for a decade or more.

Choosing a dwarf conifer for container life

Not every dwarf conifer suits a pot. Look for genuinely compact, slow-growing cultivars with a naturally dense habit, rather than young plants of species that will need moving within three years. Reliable choices include Picea glauca ‘Conica’, a neat green cone for a sheltered spot; Pinus mugo ‘Mops’, a rounded, very slow pine that shrugs off wind; Chamaecyparis obtusa ‘Nana Gracilis’, with its fan-like shell of foliage; Thuja occidentalis ‘Danica’ for a tight globe; and Juniperus communis ‘Compressa’, a slender grey-blue spire that looks superb in a tall terracotta pot.

• Check the eventual size — a "dwarf" that reaches two metres is a problem in a 40 cm pot.
• Match the shape to the space: columns for narrow gaps, globes for flanking a door, prostrate forms for the front of a group.
• Ask whether the plant tolerates lime. Most do; a few, such as some pines and heathers' companions, prefer acid conditions.

Compost, pot and drainage

Conifers demand free drainage above almost everything else. Standing water in a container is the quickest way to kill one, particularly in winter. A good mix is roughly three parts John Innes No. 3 to one part horticultural grit, which gives body, nutrients and open structure. For acid-lovers, use an ericaceous compost with the same grit addition. Avoid cheap, heavy, peat-free blends that slump and hold water — or improve them generously with grit and bark.

Choose a frost-proof pot: terracotta, glazed stoneware or thick plastic, at least 30 cm across for smaller subjects and 45 cm for pines. Every pot needs a clear drainage hole, and a layer of crocks or broken slate at the base helps. Stand pots on feet or bricks so water drains freely and worms and slugs have less easy access.

Planting up and positioning

Plant in early spring or early autumn, when the roots are active but the weather is kind. Set the rootball so the top of the compost sits a couple of centimetres below the rim, leaving room for watering. Firm gently, then top-dress with gravel or slate chippings — this suppresses weeds, keeps the collar dry and sets off the foliage beautifully.

Almost all dwarf conifers want full sun: at least six hours in summer, ideally with the pot shaded from the fiercest midday heat so the roots stay cool. Shelter matters more than most gardeners expect. A position exposed to freezing east winds will scorch foliage, so a spot against a wall or fence, out of the worst blast, gives the best results.

Watering, feeding and the winter dormancy question

Watering is where most container conifers are lost. Through spring and summer, water thoroughly when the top two or three centimetres of compost feel dry, letting the excess run out of the base. Little and often is worse than useless — it wets only the surface and leaves the lower roots dry. A thorough soak once or twice a week in hot spells beats a daily sprinkle.

Feeding should be modest. Conifers resent being pushed. Use a slow-release fertiliser at planting in spring, or a dilute liquid seaweed feed monthly from April to July. Stop feeding by late July so growth hardens before winter.

Winter is the part people forget. Evergreen needles keep losing water all through the dormant season, especially on bright, windy days, but frozen compost cannot replace it. So:

• Water on mild, frost-free days whenever the compost is dry — a small amount is plenty.
• Never leave pots sitting in a saucer of water during winter rain.
• Raise pots onto feet and, in hard frost, wrap the container in hessian or bubble wrap to protect roots, while leaving the foliage open to the air.
• Move the most tender cultivars against a sheltered wall in the coldest weeks.

Repotting, shaping and keeping plants healthy

Plan on repotting every three to four years, in early spring or early autumn. Move the plant into a container only two to five centimetres wider — a huge leap of pot size leaves too much wet compost around the roots. Tease out the outer roots, trim any that are circling, and replant in fresh gritty mix. If the plant has reached its ideal size, repot into the same pot after trimming a little of the rootball and refreshing the compost.

Shaping is light work: pinch out the growing tips of pines in late spring to keep them dense, and snip out any reverted green shoots on variegated or golden cultivars as soon as you spot them. Watch for vine weevil grubs, the great enemy of container conifers — tell-tale notching on the leaves and plants that wobble in the compost are the signs. Biological nematodes watered in during late summer are the cleanest control. With sun, sharp drainage, patient watering and a fresh start every few years, a dwarf conifer will reward you with year-round structure for far longer than any bedding scheme.