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. David 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, finely-pointed sepals, broadly elliptical to almost round terminal leaflet and glabrescent stem with some prickles patent.
Rubus davisii is a low-arching species, isolated bushes 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. 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 (cupped). The petals are bright pink to pale pink in colour, but often 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, so when viewed from the side may appear equal to or only just longer the styles. Filaments are white or pale pink with glabrous anthers. Styles may be greenish or yellowish, or sometimes pink or purplish based. Young carpels are pilose (with long hairs).
Sepals are somewhat grey-felted in appearance, due to long, shaggy hairs and the presence of short to medium-length acicles. They appear whitish-bordered, especially on the tight buds. They are sometimes short-pointed, but more often long-pointed with aciculate tips. Some specimens shown here have long, slender, leafy tips.
Leaves are a dull yellowish green colour, glabrous and matt above; leaflets are 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 and only slightly undulate. Leaflets are generally flat, or with the sides slightly folded inwards. Only the younger leaflets (top left leaf in photo below) and old, exposed ones (last photo below) are 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 also more strongly grey-felted.
The primocane (first-year stem) is bluntly angled with furrowed sides, dark red to purple, generally only with scattered long hairs, but sometimes more hairy on older growth in exposed situations or almost glabrous. Prickles are slightly declining and sometimes slightly curved but some are usually almost patent. They are roughly as long as the width of the stem 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.