This bramble was described by David Allen in Watsonia in 1998 on the basis of specimens collected in the 1890s from Somerset and Dorset, and in the 1960s from Pembrokeshire by T.A.W. Davis, after whom it is named. Allen also recorded it from south Hampshire and Jersey. In Dorset it is common on dry heathy habitats on the Isle of Purbeck. In the Atlas of British and Irish Brambles it was treated as synonymous with R. villicauliformis, a species of damp moorland in south-west England, but David remarked in an article that it is
amply different from that. Its main features are pink, obovate, widely spaced petals, broadly elliptical to almost round terminal leaflet and glabrescent stem with some prickles patent.
Rubus davisii is a low-arching species, isolated bushes often reaching no more than about 75cm in height. It often sends out first year stems which run parallel to the ground. The inflorescence is a broad, flat-topped pyramid of flowers borne on ascending branches and congested at the apex. The uppermost leaves are either trifoliate or consist of a single leaflet (note the similarity of the terminal panicle leafets in the photos above and below, which were photographed in three different localities). The rachis is green or dark red, moderately hairy, with long patent, declining or curved prickles, which may be numerous.
Flowers are about 2.5-3cm across with petals widely spaced but slightly curving inwards. The petals are bright pink to pale pink in colour, but may bleach white in the sun. They are variable in length (8-13 x 5-7mm) but tend to be obovate with a rounded and sometimes notched apex and the sides narrowed towards the base.
The stamens are quite long, particularly the outer ones, but are not particularly dense and tend to splay out quite widely, revealing the green or yellow styles; so when viewed from the side they appear to equal or only just overtop the styles. Filaments are white or pale pink with glabrous anthers. Styles may be pink or purplish at the base. Young carpels are pilose (with long hairs).
Sepals are pubescent with some obvious acicles. They appear narrowly whitish-bordered, especially on the tight buds. They are usually long pointed with aciculate tips. Some specimens shown here have long, slender, leafy tips.
The leaves and stems are somewhat similar to those of R. purbeckensis, with which it sometimes occurs. The leaves are dull yellowish green, glabrous and matt above; the leaflets often slightly imbricate. The terminal leaflet varies in shape from ovate to broadly elliptical to almost round, with a relatively short cuspidate to acuminate apex (sometimes quite long) and an emarginate base. The margin is finely dentate to serrate (in contrast to the coarsely serrate leaf of R. purbeckensis) and only slightly undulate. Leaflets are generally flat, or with the sides slightly folded inwards (younger and old, exposed leaflets may be slightly plicate or rugose in texture).
Leaflets are thinly greenish-grey felted below, though may be more strongly grey-felted in exposed situations. The panicle leaflets are similar below.
The first-year stem is bluntly angled with furrowed sides, brownish-red, becoming dark reddish-purple, generally only with scattered long hairs, but sometimes more hairy on older growth in exposed situations. Prickles are slightly declining and sometimes slightly curved but some are almost patent. They are roughly as long as the stem diamater with a broad base the same colour as the stem and a contrasting yellow tip. The stem has abundant pale orange sessile glands but this species has no stalked glands on the stem or panicle.