Why coastal wildflowers earn their place

Britain's coastal wildflowers are among the toughest, most generous plants you can grow. They evolved on cliff ledges, shingle banks and wind-scoured turf, in thin, hungry soils that most garden plants would sulk in. That makes them perfectly suited to the dry, sunny, free-draining corners of a modern garden — the gravel border, the windy front bed, the shallow pot by the door — and they give back far more than they ask for.

Three species are ideal starting points: sea thrift (Armeria maritima), kidney vetch (Anthyllis vulneraria) and sea campion (Silene uniflora). All three are easy from seed, all three are valuable to wildlife, and all three will tolerate salt-laden wind and long dry spells once established.

Drainage first, fertility last

Before you sow a single seed, sort out the soil. These plants want sharp drainage and low fertility. A gravel garden is ideal: spread 5–8cm of 10mm horticultural grit or pea gravel over a base of sand and subsoil, and plant or sow directly into it. If your soil is heavy clay, do not fight it — build a raised bed at least 30cm deep and fill it with a gritty, loam-based mix.

For pots, use roughly one part loam-based compost to one part horticultural grit, with a generous layer of crocks or gravel in the base. Terracotta is better than plastic here, because it dries out faster and lets the roots breathe.

The single most common mistake is being too kind. Avoid rich fertiliser and manure entirely. Feed these plants well and you get soft, floppy, leafy growth that flops open in the middle, flowers poorly, and rots in a wet winter. On poor ground they stay tight, compact and long-lived. Do not add compost to the planting hole either — plain, gritty soil is what they want.

Sea thrift: the mainstay of the coastal border

Sea thrift forms neat evergreen cushions of narrow, grassy leaves, topped from April to July with stiff stems carrying globes of pink flowers. Give it full sun and a gritty surface and it will often give you a second, lighter flush in late summer if you deadhead the first.

Sow thrift on the surface and barely cover the seed, as light helps germination. Space plants 20–25cm apart; they knit together into a low, weed-suppressing carpet within a couple of seasons. Shearing the cushions lightly with shears straight after flowering keeps them dense and stops them going woody in the centre. A white form is available and looks superb against dark gravel.

Kidney vetch, sea campion and good companions

Kidney vetch is the one to grow if you want butterflies. Its yellow, sometimes orange-flushed, woolly flowerheads appear from May to August, and it is the essential larval food plant of the small blue butterfly — the caterpillars will feed on nothing else. It prefers a little lime in the soil, so add a handful of garden lime or crushed shell grit to the mix if your ground is naturally acid. It is short-lived but self-seeds freely in gravel.

Sea campion makes low mats of grey-green leaves with white flowers whose calyxes inflate into curious bladders. It is night-scented and moth-pollinated, so plant it where you will brush past it in the evening. Like kidney vetch, it is a short-lived perennial that keeps itself going by seeding into open gravel.

Good companions to scatter among them include viper's bugloss, wild carrot, sea holly and yellow horned poppy. Leave gaps of bare gravel between plants — that is where seedlings will establish, and where ground beetles and solitary bees will nest.

Sow in autumn for the strongest plants

Autumn sowing, ideally from early September to late October, gives the best results. The seed gets a natural spell of cold, damp weather over winter, which breaks dormancy and produces stockier, more resilient plants than a spring sowing. A March to April sowing also works, but germination tends to be more erratic.

• Sow thinly on the surface of a gritty seed compost and press the seed in gently; do not bury it deeply.
• Top with a thin layer of fine grit or vermiculite to hold moisture and deter moss and liverwort.
• Water from below, or use a fine rose, and never let the compost dry out while seeds are germinating.
• Keep trays outdoors in a cold frame or sheltered spot; most species germinate within three to six weeks in mild weather, though some will wait until spring.
• Prick out seedlings as soon as they are large enough to handle, into deep pots — thrift and sea campion resent root disturbance and have a pronounced taproot.

Aftercare and the wildlife you will attract

In their first summer, keep young plants watered during dry spells, then gradually wean them off. By the second year they should need no irrigation at all beyond what the weather provides. Top-dress around them with grit each spring to suppress weeds and keep the collar of the plant dry, and resist any temptation to feed.

Leave the seedheads standing through winter. They feed goldfinches and linnets, shelter overwintering insects, and provide the structure that makes a gravel garden look intentional in January. Cut back the spent flower stems of thrift and campion in early spring rather than autumn.

Within a season or two you should see carder and leafcutter bees working the thrift, small blues investigating the kidney vetch, and moths visiting the campion after dusk. That is the quiet reward of a coastal planting: a garden that looks after itself, asks for almost nothing, and hums with life from April onwards.