Coastal gardens: plants that thrive by the sea

What the sea asks of a plant

Gardening within sight or sound of the waves is a particular pleasure, but it comes with a particular set of rules. Salt-laden wind scours leaves, dries buds and burns anything tender. The soil is often thin, sandy or full of shingle, draining so fast that summer rain seems to vanish before it reaches the roots. And yet the coast is also blessed with brilliant light, mild winters and a long growing season that inland gardeners can only envy.

The trick is to stop fighting the conditions and start choosing plants that already know how to cope. On exposed cliffs and dunes, nature has done the research for us: the plants growing wild out there are precisely the ones that will settle happily into a coastal border.

Front-line plants for the grimiest spots

Start where the wind hits hardest. Sea thrift (Armeria maritima) is the classic: tight evergreen cushions of narrow green leaves, studded from April to July with pink pom-pom flowers on stiff stems. It shrugs off spray, tolerates poor soil and looks superb edging a path or tumbling over a low wall.

Alongside it, try these reliable stalwarts:

• Sea campion (Silene uniflora) – low grey-green mats with white flowers, happy in gravel and shingle.
• Sea kale (Crambe maritima) – big, crinkled blue-grey leaves and clouds of white flowers in early summer; superb in a sunny gravel bed.
• Sea holly (Eryngium) – steely blue, thistle-like heads that keep their colour well into autumn and dry beautifully.
• Red valerian (Centranthus ruber) – self-seeds into walls and cracks; the white form is quieter if you find the pink too loud.
• Stonecrops (Sedum) – fleshy, drought-proof and loved by late bees.

Grey leaves, aromatic herbs and the Mediterranean palette

If you look closely at plants that thrive by the sea, a pattern emerges: grey, furry or waxy leaves almost always mean salt tolerance. Those fine hairs and waxy coatings trap moisture and deflect spray, which is why the Mediterranean palette works so well on a British coast.

Lavender is the obvious starting point, and English lavender (Lavandula angustifolia) is hardier and more compact than the French and Spanish kinds. Plant it in full sun with grit worked into the planting hole and it will reward you for years. Rosemary, thyme, oregano, sage and cotton lavender (Santolina) all belong in the same sunny, free-draining company, as does the silvery curry plant and Cistus, whose papery flowers are a joy in early summer.

Keep them lean. Rich, heavily fed soil produces soft, sappy growth that salt wind shreds in a single gale. A handful of compost in spring is plenty.

Hardy geraniums and other quiet heroes

Not everything by the sea has to be silver and spiky. Hardy geraniums are among the most useful plants in a coastal garden, flowering for months and asking for almost nothing. Geranium macrorrhizum makes dense, weed-suppressing ground cover in shade or sun; G. sanguineum and G. x cantabrigiense are wonderful in the front of a border, their magenta, pink or white flowers repeating into autumn.

Fill the gaps around them with fuchsia (F. magellanica is the hardiest), hebe, escallonia, crocosmia, alchemilla and anemones. For a bolder statement, hydrangeas adore the mild, damp west coast and will flower generously in partial shade, their colour shifting with the soil.

Work with the soil and the wind

Preparation matters more here than almost anywhere else. Plant in autumn, while the soil is still warm, so roots establish before the gales arrive. Improve thin, sandy ground with plenty of well-rotted organic matter, but add grit to heavy clay so winter drainage stays sharp. A mulch of compost or seaweed in spring keeps moisture in and weeds down.

Shelter is your greatest ally, but it must be permeable. A solid fence or dense wall simply deflects the wind over the top, creating damaging turbulence on the leeward side. Instead, use open slatted fencing, woven hurdles, or a mesh windbreak fixed to posts – ideally at about 50 per cent porosity – which filters the wind and slows it down. Plant a loose hedge of tamarisk, griselinia, Elaeagnus or sea buckthorn a metre or two back from the boundary and let it grow tall enough to take the brunt.

Water new plants generously for the first two summers. After that, most of the plants listed here will look after themselves.

Containers, clipping and a note on timing

If your garden is a balcony or a paved courtyard, containers are perfectly workable – just use a gritty, soil-based compost and raise pots onto feet so surplus water drains away. Thrift, lavender, rosemary, sedums and dwarf pinks all do well, though they will need more watering than plants in open ground.

A little light clipping keeps coastal plants in shape. Trim lavender and santolina immediately after flowering, shear back thrift and helianthemum in late summer, and remove faded flower heads from eryngium if you want the seedheads to hold their shape. Leave the seedheads of sea holly and crocosmia standing through winter for the birds, and cut back to the base in early spring as new growth appears.

Coastal gardening rewards a light touch and a bit of local knowledge. Watch what grows in the lanes and cliff-top paths near you, and you will soon have a garden that looks settled, generous and entirely at home in the salt air.