Clay in summer: a soil of extremes

Heavy clay is a soil that swings. In February it is a cold, grey sponge that holds your boot; by August the same ground has cracked into plates wide enough to take a finger. Add a week of thunderstorms and it floods, then sets like pot again. Gardening on clay is really a lesson in patience, and nowhere is that clearer than in the list of plants that actually survive it.

The good news is that Britain has an abundance of native grasses that evolved on exactly this kind of ground: the floodplain meadows of the Midlands, the fen edges of East Anglia, the rushy pastures of the wet west. They expect water to arrive without warning and to vanish just as suddenly. Once their roots are down — usually by the second summer — they are remarkably hard to kill.

The dependable tussock makers

Tufted hair grass (Deschampsia cespitosa) is the great survivor of British clay. Many gardeners spend years trying to remove it; wiser ones plant it deliberately. It is semi-evergreen, unfussy about compaction, happy in standing water in winter, and in July it throws up airy panicles of silver-purple that catch low evening light beautifully. The straight species is best for rough ground and wildlife corners; there are tidier clump-forming selections if you want it in a border.

Purple moor-grass (Molinia caerulea) is its natural companion. It wants clay that sits wet through winter and bakes in summer, and it rewards that treatment with fine purple flower spikes from late July and foliage that turns a soft straw colour in autumn. Leave the tussocks standing through winter — they shelter overwintering insects — and cut them back hard in February or early March, before new growth starts.

For really sodden hollows, greater tussock sedge (Carex paniculata) builds raised hummocks of root and old leaf that lift the plant clear of the water. It is technically a sedge rather than a grass, but it does the same job and looks superb beside a pond edge.

For the boggy corner that never dries

• Common reed (Phragmites australis) — the big one. Magnificent height, rustling seed heads, superb for invertebrates. It runs by rhizome, so give it a barrier or plenty of space.
• Reed canary grass (Phalaris arundinacea) — quick, tall and ribbon-striped, excellent for a wet boundary. Plant it where a bit of thuggishness is welcome.
• Pendulous sedge (Carex pendula) — arching catkins, self-seeds freely, so deadhead if you don't want it about the place.
• Soft rush (Juncus effusus) — a rush, not a grass, but the plant that tells you honestly what your drainage is doing. Keep it as a feature rather than letting it colonise everything.

Grasses that keep a meadow looking like a meadow

If you are sowing rather than planting, build a mixture rather than a monoculture. Meadow foxtail (Alopecurus pratensis) flowers early and softens the sward in May and June. Crested dog's-tail (Cynosurus cristatus) is fine, tufty and long-lived, and tolerates heavy ground better than most. Yorkshire fog (Holcus lanatus) is woefully undervalued: grey-green, velvet-soft, and covered in dew it is one of the prettiest things on a July morning. Add sweet vernal grass for the scent of hay, and red fescue on any drier ridge or slope. On a clay site, a diverse mix always outperforms a single species.

Getting them established: practical notes

• Plant in early autumn or spring, when the soil is workable but not sodden. Never dig or tread clay when it is wet — you will make the pan worse.
• Improve the planting hole, not the whole site. A luxurious pocket in poor clay encourages lazy, shallow roots.
• Mulch with coarse compost or grit to stop the surface panning and sealing over.
• Water through the first summer, especially during a dry spell. After that, established natives should fend for themselves.
• Cut most meadow grasses once, in late summer, and take the cuttings away. Nutrient removal is what keeps a meadow diverse.
• Expect weeds in year one. Keep cutting, and don't panic.

Reading the weather in the grasses

Part of the pleasure of these plants is that they write the season down. After a downpour, reed canary grass gleams and the tussocks stand in silver water. In drought, the molinia bleaches to pale gold while the sedges stay green in their damp hummocks. Wind moves through a stand of common reed like something alive, and the sound alone is worth the space.

Sit out with a notebook on a wet July evening and you will find the grasses are the record of every storm and dry spell the year has thrown at them. That is wetland nature writing at its simplest: no great drama, just clay, water, and a few resilient British grasses holding the whole thing together.