Barbarea vulgaris subsp. arcuata

I last saw this variant of Wintercress (Barbarea vulgaris) in 2017 and had been starting to doubt myself. So I was glad to find a colony at the weekend, within a kilometre of my previous record, at Skelton Grange in Leeds (VC64).

This is a taxon that seems to have passed British botanists by in recent years, but Google suggests that it is widely accepted in mainland Europe. In particular, studies in Denmark have concluded that it is genetically distinct from subsp. vulgaris, and that it also comprises two genetically distinct forms (one with glabrous leaves, as per my plants, and another with hairy leaves). Whether the genetic differences justify recognition at subspecies level is perhaps debatable.

Sell & Murrell provide a description of this plant (as var. arcuata), but it is not too challenging to identify once you are certain of the species identification and it is in fruit. Subsp. vulgaris has more or less erect fruit orientated close to the alignment of the stem (and also perhaps more densely arranged as well), whereas subsp. arcuata has widely spreading fruit +/- curving upwards.

Subsp. vulgaris seems to be common everywhere, while I suspect subsp. arcuata may be of introduced origin (at least in Yorkshire). Photographs of both are provided below. There are also several informative herbarium sheets of subsp. arcuata in Herbaria@Home, for example.

Subsp. arcuata

Subsp. vulgaris.