This bramble is mainly recorded in the southern half of England but is commonest in Hampshire and parts of neighbouring counties. It is very easy to recognise by its narrow white petals which are often contorted, combined with a typical Hystrican stem which has numerous prickles of varying sizes and stalked glands.
This is a tall-growing species which can develop robust stems. When well developed the panicle is quite open, with numerous flowers. It usually has several 1 or 3-foliate leaves with narrow leaflets along the upper part, including one or two in the terminal cluster of flowers (though not evident in the first photo below). The rachis of the panicle is flexuose (zigzag), densely pubescent and strongly glandular, including short-stalked glands and longer gland-tipped acicles and pricklets, which are densest near the apex. The main prickles are more numerous lower down the rachis.
Flowers are about 2.5cm in diameter with pure white narrow elliptical petals, varying from about 9-14mm long (average c.12mm) x 6-7mm wide. Typically they are curled inwards or pinched inwards at the apex, and widely separated. The stamens are distinctly longer than the styles, which are pale yellow but can become reddish at the base. Sepals have long, fine points and sometimes leafy tips. These photos indicate that they are mostly patent at flowering but become loosely reflexed when the petals drop.
A similar species in the south-west R. rilstonei, has shorter styles and more deeply incised leaves. R. berchieriensis also has similar flowers but more obvious red styles, flat petals and no hairs on the stem.
Leaflets are somewhat yellowish-green, glabrous above (except when young), pale green and softly pubescent below. The terminal leaflet averages 8 x 5.5 cm (rarely a centimeter longer or shorter, but not 12 x 7cm as stated by Edees & Newton). It is elliptical to slightly obovate, or sometimes slightly ovate, with a long acuminate apex. The margin is coarsely serrate (almost incised). Leaflets can be flat to slightly convex and smooth to moderately textured (becoming pleated or somewhat rugose with an undulate margin in more exposed situations).
Underside of the leaf above:
Stems are flat-sided, become deep reddish-purple in the sun and have a whitish waxy (pruinose) coating. They are moderately hairy and have abundant yellow-ended prickles, pricklets and acicles of varying sizes, many of which are gland-tipped. The largest prickles on the angles are about equal to the stem diameter.