At the end of September we spent another week in Wells-next-the-Sea in North Norfolk, staying in a holiday cottage not very far from the quay. Our stay coincided with the last week of warm summer weather and we spent every day walking or cycling, looking at flowers and insects.
Sea Aster, Aster tripolium (a.k.a. Tripolium pannonicum), is a short-lived perennial that grows on salt marshes, on muddy sea-banks, tidal river banks and in brackish ditches. In the west of the British Isles, where the coast is rockier, it can be found growing on exposed sea cliffs and among rocks. Because of its adaptability, Sea Aster can be found around most of the coast of the British Isles. It is a halophyte – a plant that will grow happily in soils or waters containing high concentrations of salt. Like Danish Scurvygrass, Sea Aster has recently colonised the edges of roads that have been treated with salt, although to a much lesser extent.
Sea Aster has semi-succulent, strap-like leaves and stems. The plant is a member of the Daisy Family, the Asteraceae. It flowers from July to October and each flower head is a composite flower, made up of many individual, tiny flowers known as florets.
There are two varieties of Sea Aster in the British Isles, separated by their flower structure. Flowers of Aster tripolium var. tripolium have a central group of yellow disc florets surrounded by pale mauve or white ray florets, while Aster tripolium var. discoideus lacks the ray florets. My photograph above shows the rayless (discoideus) variety, which predominates in many parts of East Anglia, though the rayed form (shown in my photo at the end of this post and also here and here) is the commoner form in much of the British Isles.
Outside the British Isles, Sea Aster grows around most of the coasts of Northern Europe, north to North Norway (where it is rare), in Finland and south to Portugal and the Mediterranean. It occurs as far east as Japan, but it is an endangered plant in the Tokyo area, threatened by coastal development, encroachment of saline habitats by reed, and inappropriate management of flood defences. Because of this, Professor Noboru Kuramoto from Meiji University in Japan is investigating the distribution and ecology of Sea Aster in Britain and Japan, with the assistance of The Essex Field Club.
Sea Aster is edible, though I haven’t tried it yet. The leaves can be cooked or pickled and the BBC Food website has a recipe for Pan-fried Salmon with Aster tripolium and Scallop Broth, which sounds good, as do Sea Aster Fish Bake and the even simpler Buttered Sea Aster, on the Eatweeds website. The Galloway Wild Foods website suggests pickling Sea Aster in slightly sweetened white wine vinegar with herbs, such as Coriander leaves, Wild Thyme and green (unripe) Alexanders seeds. If you live near the coast, it is possible to forage for Sea Aster. You may be able to grow the plant in your garden as well. In his book “Around The World In 80 Plants” Stephen Barstow relates how managed to grow Sea Aster in his garden in Norway, in bed of sand and also in a bucket of fresh water.
Sea Aster flowers are attractive to butterflies such as the Red Admiral. But they are particularly associated with the Sea Aster Mining Bee, Colletes halophilus. In the UK, this charismatic insect is restricted to the coast of Southern and Eastern England, from the Humber Estuary down to Dorset, with most colonies on the East Anglia coast and the Thames Estuary. The bee emerges in August when Sea Aster is in full flower and flies until the end of September.
Although we were at the end of the flight period, we were able to see several female Sea Aster Mining Bees and we followed them as they flew from one flower head to another, wrapping their bodies around the Sea Aster flowers as they gathered pollen. We were also lucky enough to find a nest site, with lots of individual nest holes in a bank. However, we were too late in the season to witness a mating ball, where a female bee emerges from its nest hole and is surrounded by a cluster of males.