Sea lavender and glasswort: a salt marsh through the seasons

The zones, from mudflat to dike foot

Walking inland from the low flats you pass through bands that repeat with reassuring stubbornness all along this coast. First the pioneer zone, bare mud with glasswort, Salicornia, standing in it like short green candles, and the coarse tussocks of cordgrass holding sediment. Then the low marsh, where common saltmarsh grass, Puccinellia maritima, forms a close turf cut by creeks. Higher again comes sea lavender, Limonium vulgare, sea purslane along the creek lips, and sea aster. Nearest the dike the salt thins and ordinary grassland species creep in.

The bands are narrow here, sometimes only tens of metres, so the whole sequence can be crossed in a few minutes. I find it useful to stop at each change of texture underfoot and write down what has appeared and what has dropped out. After a season of doing this I could estimate the tidal level of a patch of marsh from the plants alone, which is a small and completely useless skill that I enjoy enormously.

• Pioneer zone: glasswort on open mud, cordgrass tussocks
• Low marsh: saltmarsh grass turf, creeks with steep lips
• Middle and high marsh: sea lavender, sea purslane, sea aster
• Dike foot: salt fading out, coarse grasses taking over

April and May: a marsh that looks empty

Early spring is the season most people would describe as nothing happening. The pioneer flats are bare brown mud scoured by winter, last year's aster stems lie flattened, and the turf is grey-green and short. It is also the easiest time to read the structure of the place, because the creeks are exposed to their full depth and the subtle steps between zones are not hidden under growth. I take most of my sketches in April for exactly that reason.

Glasswort seedlings appear as scattered red-green pinpricks on the mud, so small that a first glance registers them as algae. By late May they have become obvious, and the pioneer zone changes from brown to a stippled green over about a fortnight. Breeding birds are settling on the higher marsh at the same time, so this is the period when I keep to the dike and the marked paths and do my looking through binoculars.

July: the fortnight of purple

Sea lavender flowers across the middle marsh in July, and for perhaps two weeks the plain turns a soft lilac that reads, from the dike, as a haze rather than as individual flowers. Up close the flower heads are small, dry and papery, and they hold their colour long after they die, which is why the marsh keeps a faded purple cast into August. The Dutch name, lamsoor, is more often heard than the English one, and the colour is exactly the one that gave the plant both names.

Timing varies by a week or more between years and between the western and eastern marshes. In 2024 the western marsh I watch was at its best around 14 July; in 2025 the same stretch peaked closer to the 21st after a cold June. If you want the colour, the reliable approach is to go twice a fortnight apart rather than trying to predict it. The light in the hour before sunset is worth more than the exact date.

Autumn and winter: rust, seed and salt

In September the glasswort turns. A pioneer flat that was green in August becomes coral, then deep rust and finally a dull brick, and on a bright still morning after the first cold nights the colour is the most startling thing on this coast. Sea aster flowers at the same time, mauve daisies scattered through the low marsh, and the two together are the reason my October notebook pages are the messiest of the year.

Winter reduces everything to stems and mud. Storm tides flatten the marsh, leave lines of drift along the high-water mark, and deposit a fresh skim of silt that is the whole reason the surface keeps rising. I walk the dike rather than the plain in January and February, partly for footing and partly to avoid trampling a surface that is soft, saturated and slow to recover. The plants are all still there; they are simply waiting, a few centimetres below my boots.