Far From Rottingdean

I continue to be fascinated by this invasive alien which occupies the riverside shingle between the Red-roofed Hut and the Riverside Blockhouse. Last year, I wrote a short article about it for the Friends’ Newsletter. Since a bit of time has now passed, perhaps I’ll repeat it here:

FORTY MILES FROM ROTTINGDEAN

…and very much further from Sicily, whence it originated, a little purple flower has travelled, first with assistance of humans then, putatively of gulls, to find a home by the rivermouth at Rye Harbour. Just beyond Norton’s Hut you can see the colourful curvilinear mats of Rottingdean Sea Lavender (Limonium hypblaeum) hunkered down in a hollow behind a fresh bank of pebbles thrown up by the latest over-topping tide.

It was cultivated as a garden plant at the White Horse Hotel, Rottingdean since at least the early 1950s and first recorded as an escape on the nearby chalk cliffs in 1979. It was first noted on the nature reserve by the Rother around 2002 but its UK distribution remains very limited.

This low-lying plant grows in dense rosettes that smother the shingle and has spread quickly in this one spot on the reserve. As with many alien species, it has the potential to become invasive, which it has in other countries. There were initial concerns that it would compete for space with the native Sea Heath (Frankenia laevis ) which was formerly restricted to a small patch of the same habitat. However Sea Heath has now spread across large parts of Flat Beach and the new saltmarsh habitat on the far side of the path, so is no longer in jeopardy. That’s unless Rottingdean Sea Lavender should follow…so there’s a watching brief on its progress. But for the present it can be appreciated as a photogenic plant favoured by insects (including the scarce Saltmarsh Horsefly, Silvery Leaf-Cutter Bee & Brown-banded Bee) in summer and birds (including the rare Twite and Shore Lark) foraging its seeds in winter.

I’m intrigued by the sharply defined limits of its growth areas and by the vigorous flowering at the colonising edges. I’ve only noticed the latter this year, but that could be my lack of attention. You can see both features in the photo above, where the marginal tufts are larger and covered in flowers whereas older plants within the patch remain as deep crimson leaf rosettes, perhaps with much reduced flowering.

My guess is that those vigorous lines are the expansionist vanguard, dumping loads of seed onto ground as yet unoccupied. If anyone knows one way or the other, I’d be pleased to be confirmed or corrected.

The palest, freshest, most disturbed shingle is generally where the river over-topped on an exceptionally high tide (as in the foreground of the photo below) perhaps burying the existent plants, but I’m puzzled about the curving area in the two photos above. It looks too far from the river to result from a tidal wash but is too wide and discontinuous to be an animal track.

Within the growth areas, the rosettes bind the shingle, stabilising it so that animal and human trampling has little effect. In the photo above you can see that the pebbles look whiter than those surrounding it. The dead foliage provides the beginnings of a soil and the undisturbed stones are more readily encrusted with lichens.

A characteristic which hardyl shows i na photo but is evident to the eye, especially in raking light, is the way plants follow and therefore emphasise contours otherwise too subtle to notice in a rhythmic mesh of curves and diagonals.

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