Old painting of Sea Aster, by Dutch artist Georgius Jacobus Johannes van Os, Public domain, via Wikimedia Commons.
In the world of flowers, the namer Aster conjures up images of cottage gardens in late summer and autumn, when the many aster varieties provide splashes of pale purple. Aster is Latin for ‘star’ and the flowers are indeed star-like. In botanical terms, the genus Aster once had 600 species scattered throughout Europe, Asia and North America. But now, many have been kicked out of Aster and put into various other genera, leaving about 180 true Aster species.
This image shows the lanceolate succulent leaves, the yellow disc florets and the lilac ray florets. Insects can be seen visiting the flowers on the right-hand side. Image: Chris Jeffree.
In Britain, according to the 1991 first edition of Stace’s New Flora of the British Isles, there were nine wild asters, including Aster tripolium the Sea Aster; but alas in the fourth edition (2019) there are none at all. Sea Aster has become Tripolium pannonicum, the sole member of a genus called Tripolium.
For a highly ‘readable’ account of why Aster has been split up into smaller genera, there is an excellent article here from the Royal Horticultural Society.
In this and many other images, the flowers look ‘dishevelled’. Image: Chris Jeffree.
You may find Sea Aster during coastal walks. It is a true halophyte, with fleshy leaves and a tolerance of salty conditions. Shennan et al (1987) made careful measurements of its growth rate in culture solutions resembling sea water and found that growth was not inhibited until the salt in the solution was around two-thirds the strength of sea water. However, it grew well in very low salt solutions whereas the most extreme halophytes (eg Samphire) do not. They appear to require at least some salt to thrive. Other researchers have shown Sea Aster’s requirement for salt during germination.
In Sea Aster the phyllaries (the green bracts around the flower head) are fewer and blunter than in all other asters. Image: Chris Jeffree.
Unlike some halophytes, the plant has no secretory elements such as salt glands. It does however have air spaces in its root tissues to allow oxygen to diffuse into the roots when it is flooded by tidal flows.
It is found in salt marshes, tidal estuaries and various maritime sites throughout the British Isles. It can also be seen at saline areas inland and like several halophytes it has sometimes colonised salted roadsides (the A63 in East Yorkshire, around Hull). Almost any salty place suits it: Lee (1977) notes its occurrence in brine-springs (these are curious formations found mostly in Cheshire, Staffordshire and Worcestershire). In a very early paper, we read about its occurrence inland, at the Cerebos Saltworks, Greatham, Co. Durham (Clapham et al 1942). It is interesting to compare Clapham’s 1940 distribution map with the present one. There are only small changes since the 1940s, although the BSBI Atlas 2020 indicates a decline in more recent decades (Stroh et al 2020).
Extensive stand of Sea Aster. Attribution: Stefan.lefnaer, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons.
It is an annual or biennial plant (earlier authors said it was a short-lived perennial, and perhaps it sometimes is indeed a perennial), germinating or sprouting in April and May, flowering in late summer and autumn, and dying back in winter. Even in winter, a few sprouts can be seen. The flowers are very like the garden ‘Michaelmas Daisy’ but have been described as ‘dishevelled’. I had imagined this is because they get severely battered by the wind but now I see that most on-line images show the untidy character of the flower; so I think that ‘tidiness’ has not been a useful attribute in natural selection for the case of Sea Aster. Of course, the garden Michaelmas Daisies (now in the genus Symphyotrichum) have been selected by humans for their tidy star-like flowers. Symphyotrichum species exist in the wild as naturalised aliens. They are quite difficult to tell apart but they do provide colour to much waste ground.
British and Irish distribution of Sea Aster. Data from the BSBI.
The untidiness of the flower does not deter insect pollinators. There are many, including bees, flies, beetles, moths & butterflies. The central disc-florets are hermaphrodite and protandrous and the colourful ray florets are female only. The ray florets are occasionally absent leaving the yellow disc florets looking like groundsel. There is abundant seed-set, said to be in the range 450-1600 per plant.
Global distribution, according to GBIF (Global Biodiversity Information Facility). Note: it is one of the few European species that hasn’t reached Australia (so far).
It is good to eat. Authors of several foragers’ web-sites write enthusiastically about its tastiness and crispness, whether it be raw or pickled, fried or baked. But as with Samphire, we must be careful not to over-exploit this species and please ask the landowner for permission before making small harvests. I haven’t heard of any attempts to grow the plant for food, but I’d like to try.
The Latin name Tripolium pannonicum is a mystery to me. Tripolium is Latin for Tripoli (the second largest city in Lebanon) and pannonicum refers to the Pannonian region of Europe which includes the Great Hungarian Plain. Neither seem to have a connection to Sea Aster.
References
Clapham AR, Pearsall WH & Richards PW (1942). Biological Flora of the British Isles. No. 8. Aster tripolium L. Journal of Ecology 30, 385–395 doi:10.2307/2256580
Stroh PA et al (2020) Tripolium pannonicum (Jacq.) Dobrocz. in BSBI Online Plant Atlas 2020. https://plantatlas2020.org/atlas/2cd4p9h.7mxz8c
Shennan C, Hunt R & MacRobbie EAC (1987) Salt tolerance in Aster tripolium L. I. The effect of salinity on growth. Plant. Cell and Environment 10, 59-65.
Yuan F, Leng BY & Wang BS (2016) Progress in Studying Salt Secretion from the Salt Glands in Recretohalophytes: How Do Plants Secrete Salt? Frontiers in Plant Science [PMC free article]
©John Grace
Botany in Scotland 