Lowland Acid Grassland in May: What to Find at Ground Level

Watercolour of lowland acid heath at ground level. Blue milkwort, white heath bedstraw, rust-red sheep’s sorrel and yellow tormentil in short turf, gorse in yellow flush behind, low horizon.

Lowland acid grassland in the third week of May is the closest thing left to what southern England looked like before the plough and the fertiliser. The species that grow on it now were the species that grew everywhere three centuries ago. Find a piece and stand on it. There is not much left in the country, but where it survives it is at its peak for two weeks in mid to late May, before the coarse grasses take over and draw a curtain over everything beneath. The window is narrow and worth the effort to get to.

What it is

Lowland acid grassland is the technical name for the un-improved grassy heath that develops on sandy or gravelly soil too acid and too poor to repay agricultural improvement. It supports a specific assemblage of low-growing wildflowers, fine grasses, mosses, and lichens, with gorse in scattered clumps and bracken at the edges. It is a successional habitat: without grazing or cutting it would scrub over within thirty years. Most surviving examples are on commons, heathlands, lowland greens, and parish open spaces where the medieval right of common grazing kept the trees off until the modern grazing replaced it.

Why so little remains

The economic reason the common was left un-improved is the same reason it still supports the flora. The ground was too sandy, too acid, or too steep for arable, and nobody could think of a use for it that would repay the cost of draining, liming, and reseeding. Through the twentieth century, mechanisation and chemical fertiliser changed the calculation: ground that had been beyond economic improvement in 1800 became worth ploughing in 1950, and the un-improved grasslands were lost piece by piece. The fragments that remain were saved mostly by accident, on land that even modern agriculture could not turn a profit on.

Identifying milkwort

Down at ground level in May, the first species to look for is milkwort (Polygala vulgaris). It is a small creeping plant carrying flowers that can be pink, white, or blue, sometimes all three on a single stem. The blue is the one that catches you: a clear acid blue, not the violet-leaning shade of a bluebell, not quite like any other blue in the English flora. The flowers are arranged on short upright spikes, each about a centimetre across, the petals fused into a small hooded shape with two flared lateral wings. Milkwort flowers from mid-May to mid-July.

Heath bedstraw, sheep's sorrel, tormentil, gorse

The reliable indicator species at walking pace is heath bedstraw (Galium saxatile), a tiny white four-petalled flower less than a centimetre across, growing in dense low mats among the fine grasses. Sheep's sorrel (Rumex acetosella) is the other consistent presence, its rust-red seed spikes turning whole patches the colour of dried blood from a distance. Tormentil (Potentilla erecta) creeps along the ground between them, a small yellow four-petalled flower distinguishable from the five-petalled silverweed by the count alone. The gorse on the heath is in its second flush in late May, the new shoots catching up with the old growth from February, and on a warm afternoon the coconut scent carries across the whole open space.

The narrow window

What makes the third week of May the moment is the brevity of the window. By the second week of June the coarser grasses (false oat-grass, cock's-foot, Yorkshire fog) will have shot up to waist height and drawn a curtain over everything beneath. Right now the turf is still short enough to see through, and the small flowers are in full bloom at the level of the ankle. Get down on your hands and knees if you have to. There are species at your feet this fortnight that will not be visible again for fifty weeks.

How to find a real heath

The municipal "wildflower strip" planted on a roundabout is not the same thing. A real lowland acid grassland is a patch of unimproved land with a continuous history of low-intensity grazing or cutting, usually several centuries old. The places to look in southern England are commons, lowland greens, the New Forest, the Surrey heathlands, the Suffolk Sandlings, the Norfolk Brecks, parts of the Dorset heaths. Many are designated SSSIs and are public access land. Visit on a dry afternoon when the insects are flying; the butterflies are visible from the edge before you go in.

Sources: Plantlife species notes: Polygala vulgaris, Galium saxatile; Wildlife Trusts heathland habitat guide; JNCC, UK Habitat Classification: H1.7 Lowland dry acid grassland.