Why autumn is the kindest season on the coast

Coastal gardeners learn to work with the weather rather than against it. By September the worst of the summer drought has passed, the soil is still warm from months of sun, and the nights are cool enough to slow water loss without stopping growth. That combination is ideal for establishing plants. Anything you put in now has autumn and a usually mild coastal winter to root before the drying winds and salt spray of spring arrive.

There is another advantage to working now: the salt-laden gales tend to come later, so autumn gives you a window to settle new planting and protect it before the storms really begin. The jobs below are the ones that repay you most in a garden within sight or sound of the sea.

Plant natives while the soil is still warm

Aim to finish planting by mid-October in most coastal areas, or by early November in the milder south-west. The soil is still workable, and roots will grow on until temperatures drop below about 5°C. Choose British natives that already cope with wind, salt and thin, free-draining ground. They need less mollycoddling and will feed the local wildlife.

• Sea thrift (Armeria maritima) — tight cushions of pink flowers that shrug off spray. Plant in full sun at the front of a border or in gravel.
• Sea campion (Silene uniflora) — white flowers on low, spreading mounds. Excellent for stabilising sandy or stony ground.
• Yarrow (Achillea millefolium) — flat heads of cream or pink, deeply rooted and drought-proof. A magnet for hoverflies.
• Wild carrot (Daucus carota) — lacy umbels that look wonderful among grasses. Give it poor soil to keep it compact.
• Red fescue (Festuca rubra) — a fine native grass for matrix planting. Tough, low and tolerant of salt.
• Sea holly (Eryngium maritimum) — spiny, blue-grey and architectural. It needs sharp drainage, so add grit to the planting hole.

For a fern border, autumn is arguably the best time of all. Native ferns such as hart's tongue, male fern, lady fern and soft shield fern establish quickly in warm, moist autumn soil. Water them in well, even if rain is forecast, and keep them mulched but never buried at the crown.

Mulch, but choose the right material

Mulching in autumn does three jobs at once: it insulates roots, suppresses winter weeds and slowly feeds the soil. In coastal gardens, where soil is often thin, sandy and low in organic matter, this matters enormously.

• Leaf mould is the finest mulch for ferns and woodland natives. Spread a 5–7cm layer, keeping it clear of crowns and stems.
• Garden compost suits hungry flowering natives such as yarrow and sea campion. Sieve it first so you are not sowing weeds.
• Well-rotted manure is useful on light sandy soil, but dig it in rather than leaving it on the surface where wind will take it.
• Grit or gravel around sea holly, thrift and other silver-leaved plants improves drainage and reflects light back onto the foliage.

Seaweed is a traditional coastal mulch, but check local byelaws before collecting from the shore, and never take it from living plants or protected sites. A light rinse with fresh water before use reduces surface salt.

Tidy and divide the fern border

Ferns are the stars of a coastal garden's damp, shaded corners, and autumn is when they appreciate attention. Cut back any browned or battered fronds to the base, but leave green ones in place — they will keep working until hard frost. Clear fallen leaves from the crowns, particularly around hart's tongue, where damp debris can rot the crown over winter.

Every three or four years, lift and divide congested clumps. Use a sharp spade or two forks back to back, and replant the outer, vigorous sections, discarding the woody centre. Water thoroughly and mulch with leaf mould. This is also the moment to move any fern that has outgrown its spot — they settle far better now than in spring.

If you garden on heavy clay, fork in grit and compost before replanting. Coastal ferns dislike sitting wet through winter, and good drainage is the single biggest factor in keeping them healthy.

Prepare for wind, salt and winter wet

Autumn is the last chance to get protection in place before the gales. Check stakes and ties on any young trees or shrubs and firm new plants in gently — a rocking plant will not root, especially in sandy soil.

• Shelter with woven screens or a native hedge of hawthorn, blackthorn or sea buckthorn. Solid fences cause damaging turbulence; semi-permeable barriers work better.
• Water evergreens in dry spells right through autumn. They lose moisture through their leaves all winter, and drought-stressed plants suffer most from salt burn.
• Lift pots onto feet or stones so they do not sit in standing water. Coastal winters are often wet rather than frozen.
• Leave seed heads on teasel, wild carrot and sea lavender for birds, and resist cutting everything back until late winter.

Do these jobs in the gentle weeks of early autumn and your coastal garden will go into winter anchored, fed and sheltered — ready to burst into life again come spring.