A garden that suits a round brick wall

An oast house does a great deal of talking on its own. Those round kilns of soft red brick, the leaning weatherboarding, the white cowl turning quietly on its curb — the architecture is already the main event, and a formal, geometric garden would only argue with it. Curved walls and awkward corners mean you are rarely designing for a neat rectangle anyway, so the sensible answer is a cottage garden: loose drifts, self-seeders wandering where they please, and roses leaning into the brickwork as though they have been there since the hop-drying days.

It also happens to be the most forgiving style for the Weald. Heavy Wealden clay, sticky through winter and cracking in a dry August, suits robust herbaceous perennials far better than it suits alpines or tidy bedding. Add the shelter of an old farmstead, hedgerows and a few fruit trees, and you have a genuinely kind site to work with.

Start with the soil and the wall itself

Before you buy a single plant, sort out the ground and respect the building. Oast houses were usually pointed with lime mortar, which needs to breathe and dry out. Piling wet soil and mulch against the base traps damp, and frost then spalls the brick face. Leave a clear planting gap of 45–60cm between the wall and the front of the border; a strip of gravel or cobbles in that gap looks deliberate and keeps the brickwork honest.

For the clay, dig in well-rotted manure or garden compost at roughly one barrowload per square metre, plus a couple of handfuls of horticultural grit in the worst spots. Plant in October or November, or failing that in March. Then mulch 5–8cm deep, keeping it off stems.

• South or west-facing curve of a kiln: a genuine sun-trap — rosemary, lavender, ceanothus, figs and tender salvias will all manage here.
• North and east walls: dry shade under the eaves. Pulmonaria, epimedium, Geranium macrorrhizum, brunnera and ferns will cope where little else will.
• Beneath the cowl: expect a rain shadow and a drip line. Plant nothing precious directly under the overhang.

The perennial backbone

Build the garden from tough, long-flowering perennials and it will look established within two seasons. Plant in odd-numbered groups of three or five, spaced 30–40cm apart, and let them knit together rather than leaving polite gaps.

• Geranium 'Rozanne' and G. x oxonianum — six months of flower on 45cm mounds, indifferent to clay.
• Nepeta 'Six Hills Giant' — grey-green, bee-magnet, and happy to flop over a path edge.
• Alchemilla mollis — soft chartreuse froth that seeds gently into gravel.
• Salvia nemorosa 'Caradonna' and Achillea 'Terracotta' — upright accents in deep violet and burnt orange.
• Verbena bonariensis — airy 1.2m stems that let you see the oast through them.
• Astrantia and Iris sibirica for the damper, heavier patches.

In late May, cut half your tall perennials back by a third — the old Chelsea chop. You get sturdier stems, no staking, and flowers a fortnight later, which stretches the season considerably.

Roses and climbers on the round walls

Round brickwork is superb for climbers, but only if you give them something to hold. Fix 8–10mm vine eyes into the mortar joints — never the brick faces — and run tensioned wires 30–40cm out from the wall. Train stems out horizontally and fan them; roses flower along the whole length of a stem that lies flat. Tied vertically, you get flowers only at the top.

• Warm, sunny curve: Rosa 'Gertrude Jekyll', 'Teasing Georgia' or 'Wollerton Old Hall'.
• North or east wall: 'Madame Alfred Carrière' or 'New Dawn' — both shrug off a colder aspect.
• Clematis: C. alpina and C. viticella 'Étoile Violette' are unfussy and disease-resistant. Plant 30–45cm away from the wall, angled back towards it, with the crown 5–8cm below soil level, and shade the roots with a low perennial.
• Quick cover: a hop bine over an arch — golden varieties are fast, ornamental and entirely in keeping.

Self-seeders for a wandering, relaxed feel

This is where the cottage character really comes from: plants that move themselves about. Nigella, calendula, corn poppy, cornflower, Lychnis coronaria, aquilegia, foxgloves and eryngium will all sow into gravel, path edges and any bare patch you leave open. So will verbena and alchemilla, given half a chance.

The practical trick is restraint. Don't deadhead everything — leave seed heads standing through winter for the birds and for structure, then shake seed where you want it in early spring, or simply let it fall. Keep mulch to 5cm at most, because a thick blanket smothers seedlings before they start. Gravel and cobbles make excellent nursery beds.

Then edit. In April, thin seedlings to 20–25cm apart and pull out anything that has chosen badly — in a wall, through a rose. That bit of ruthless thinning is the only real design work self-seeders ask of you.

Keeping it in hand through the year

• Late winter: cut back spent perennials and grasses, mulch, top-dress roses, prune climbers before growth starts.
• May: chop, stake with hazel peasticks, tie in new rose growth.
• Summer: deadhead selectively rather than compulsively, and water new plantings properly for their first two seasons.
• Autumn: plant bulbs — alliums, camassia, narcissi — through the borders, divide overgrown clumps, and put in bare-root roses.

Keep a path about 90cm wide, gravel or brick, so the planting reads as generous drifts rather than a jungle. And do resist over-tidying. A few collapsed stems and seed heads left standing are what make the garden feel settled against the brick — as if the oast, the roses and the clay have been getting on quietly for a very long time.