A rare member of the Sprengeliani, somewhat similar to R. sprengelii, but with broadly ovate to almost rounded leaflets. It has a similar prostrate habit, with thinly hairy stems, 3-5 leaflets, a widely diverging inflorescence (which is weakly armed) and deep rose-pink petals.
Rubus permundus was described as
plentiful over a large area under bracken at Netley Heath, Surrey, by W.C.R. Watson in his Rubi of Great Britain and Ireland. I am uncertain as to why this single colony was given a scientific name, since usually brambles are only named if they are established over a reasonably large geographical area. Perhaps it was originally thought to be conspecific with a continental species, but when later realised to be endemic to Britain was named to allow it to be referenced against an earlier determination? However, a new colony was discovered at the north end of Browndown Common, Gosport, Hampshire by David Allen and myself in 2012. The colony is similarly under bracken in a heathland area, but its extent is very limited. R. sprengelii grows nearby, which suggests that possibly R. permundus could be a hybrid of that with another species. These photos taken with flash were of plants in deep shade at Browndown in 2014 and 2016.
The flowers are distinctly larger than those of R. sprengelii, about 2.5 cm across, having broadly obovate petals. Styles are deep red and the stamens are pink at the base.
A feature of the Sprengeliani is that the stamens are about equal to the styles; in these flowers there are a few longer outer ones. Note also the sharply pointed patent sepals (similar to R. sprengelii). The lower flower also has long leafy sepals, a feature also mentioned in Watson's Rubi.
Leaves are almost glabrous above and roughly hairy below on the veins. Three or five leaflets may be present (or three with budding lobes as below). The description in Edees & Newton that the leaves are
somewhat plicate does not seem to be true of these plants, but may apply to specimens in full sun. The terminal leaflet is broadly ovate with a very short to medium acuminate tip.
The stem is rather stout, bluntly angled to almost round, turning reddish purple in sun, thinly hairy with fine, broad-based, declining prickles. Descriptions state that rare short-stalked glands may be present.