A garden that thinks it lives by the sea

Walk any clifftop path in late spring and you will meet them: tight cushions of thrift, drifts of sea campion, stonecrop studding bare rock, and hoop petticoat daffodils nodding in the turf. These are plants that shrug off salt-laden gales, thin soils, blazing light and long dry summers. They are also, mercifully, among the easiest alpines to grow — provided you give them the one thing their seaside home does best: drainage. A sunny rock garden does exactly that, and it lets you build a slope, a set of crevices and a free-draining root run in an afternoon.

Coastal alpines are not fussy about living near the sea. They are fussy about wet roots, shade and still, damp air. Sort those and the rest is a pleasure.

Choosing the right spot

Give them the sunniest, most open position you have. A gentle south- or west-facing slope is ideal, but a level bed works if you raise it. Avoid the rain-drip zone at the foot of a wall and anything shaded by shrubs or fences. Air movement is an ally, not an enemy: breezes keep foliage dry and hold fungal problems at bay. In very exposed coastal gardens, the silver and woolly-leaved alpines — Armeria maritima, Silene uniflora, Dianthus species — are the ones that sail through gales without complaint.

Height is your best drainage tool. Raising the bed by 30–45 cm does more good than any amount of grit dug into flat ground, and on heavy clay it is the only sensible approach. Build up; do not dig down.

Soil, grit and the lime question

Mix roughly equal parts by volume of good garden soil, coarse horticultural grit of 6–10 mm, and a lean humus such as leafmould or spent potting compost. Aim for a slightly hungry mix: alpines flower hardest on modest rations, and rich soil makes soft, floppy growth that rots in winter. If your ground is clay, add extra grit and sharp sand.

• Put 10 cm of rubble or broken brick at the base of a raised bed before you add the mix.
• Top-dress the finished surface with 1–2 cm of grit so the collars of plants stay dry.
• If your plants are lime-lovers — pinks, pasque flowers, basket-of-gold — use limestone or sandstone chippings. In an acid garden, stick to lime-free grit and avoid limestone.

Stone choice matters less than consistency. One type of rock, used generously, looks far better than a lucky dip of whatever was going cheap.

Building the rockwork

Bury every stone a third to a half of its depth so it sits as though it has always been there. Tilt the strata so the bedding planes run into the slope, mimicking a natural outcrop; rain then sheds off the face and trickles into the crevices where the roots are. Work from the bottom upwards, and stand back every few stones to check the shape.

Leave gaps of 5–8 cm between boulders — these are your planting pockets. Tufa, that porous limestone beloved of alpine growers, is superb for a small feature or a single showpiece stone, though local sandstone or limestone is cheaper by the barrow-load and settles in beautifully.

Planting the crevices

Spring and early autumn are the best times to plant. Tease the roots out, tuck the plant into a crevice or pocket, firm it gently with your fingers, and water it in with a soft spray. Then leave it alone. Space plants further apart than instinct suggests — they will knit together within two seasons, and crowding only encourages rot in wet weather.

Good companions to start with include Armeria maritima for pink pom-poms in early summer, Sedum anglicum for starry white flowers over tight mats, Campanula cochlearifolia for hazy blue in gravel, Pulsatilla vulgaris for silky spring bells, and Thymus or Helianthemum to spill over the front edge. Add a few Sempervivum and Saxifraga in the tightest seams, where nothing else will fit.

Tiny bulbs, big reward

Small bulbs are the secret to a rock garden that looks alive for more than six weeks. Plant them in pockets and gravel margins in early autumn, at two to three times their own depth, in groups of seven to fifteen so they read as drifts rather than accidents. Leave the foliage to yellow completely before you tidy it away.

• Narcissus bulbocodium and N. cyclamineus for February and March cheer.
• Crocus, Scilla siberica and Anemone blanda for early colour woven between the cushions.
• Cyclamen hederifolium and Muscari for late-season interest, with marbled leaves that carry on into winter.

Keeping it happy through the year

Water your rock garden only in its first summer, and thereafter just during genuinely prolonged drought — and always at the roots, never over the foliage. Winter wet kills far more alpines than frost ever will: a sodden crown rots, whereas a frozen one usually shrugs it off. The grit mulch, the raised bed and the crevices do most of this work for you. If you garden on flat, heavy ground, consider covering the whole bed with a raised pane of glass or a cloche from November to February.

Deadhead regularly to keep the flowers coming, and trim mat-forming plants lightly after flowering — but never cut back into old, bare wood, as most alpines will not regrow from it. Clear fallen leaves from crevices in autumn, watch for slugs on new shoots in spring, and you will have a patch of seaside cliff that asks almost nothing of you and gives something back in every month of the year.