A mystery at the end of the rainbow

November 19th 2017

Sunday 29th October 2017 provided, as it happened, our last day’s serious botanical recording this year.  With rain threatened later, we parked near Skiag Bridge (NC2324) at about 1030 a.m. and made a start listing the plants, after admiring a golden eagle sitting on top of a crag up the road towards Quinag.  The first cast along the shore of Loch Assynt and back to the road yielded some 80 species, including peppermint Mentha x piperata on the lochside and lesser hawkbit Leontodon saxatilis on the roadside; the latter is a fairly recent addition to the known Assynt flora, being a roadside halophyte (salt-lover), usually found near to salt and grit heaps.

We then made our way up the Quinag road and off up a small burn into limestone country, adding predictable species such as mountain avens Dryas octapetala and stopping for lunch on the south side of an outcrop, in the sun and out of a freshening northerly wind, with fine views over Loch Assynt.

After lunch, we explored a shallow winding burn and the spring-fed flushes that fed it.  This gave us the usual suspects such as long-stalked yellow-sedge Carex lepidocarpa, but also dense stands of the lime-encrusted stonewort Chara virgata, and the shiny, round, opposite leaves of brooklime, the euphoniously-named aquatic speedwell Veronica beccabunga, rare in Assynt.  There were also some curious jelly-like small lumps on stones, with harder centres, which proved, on later closer examination, to be colonies of a cyanobacterium Rivularia haematites.

The weather was beginning to look a bit threatening, so we made our way through some wire fences and old walls up to a dark limestone ridge at the eastern edge of our recording square.  The area is heavily grazed, but we did spot hard shield-fern Polystichum aculeatum deep in a crevice.  Cresting the ridge, a short-lived shower of rain was upon us, providing a spectacular rainbow over the old farmhouse at Achmore.  We then turned south, making our way back to the road, along a broad drainage ditch running through old cultivation ground south of the farmhouse.

And it was here (for the persevering amongst you) that we struck our mystery at the end of the rainbow (allowing for a little poetic licence).  The drainage ditch was almost completely covered, for over 300m, with the rounded, shallow-toothed, alternate leaves of a water plant that completely stumped us.  It didn’t help that neither flowers nor fruits were present.

It took a couple of days (and the careful tasting of a well-washed specimen, bearing in mind the risks of liver fluke) before the penny dropped, watercress, probably the species Rorippa nasturtium-aquaticum, for which there is an old record in this area.  The two species of watercress that occur, uncommonly, in Assynt appear to be restricted to the coast and limestone, but fruits are required for a definite identification.  And just for the record, our final score, for some five hours in the field, was 150 species, with a good proportion of less common ones; a great way to end the recording season.

Ian Evans and Gwen Richards

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