This is a widespread but declining species of heathlands and wood margins, which prefers damper soils. Its flowers are not particularly distinctive, having white petals with long stamens, so similar to many other species. However, combined with the finely pointed sepals, which are patent at flowering, and the leaf and stem features described below, the species can be fairly easily recognised. This is a true Sylvatican: there are no stalked glands anywhere on the plant and the leaves are not grey or white felted below.
This is a high arching species which has tall, erect stems. On heathland it will typically be found growing through bracken or scrub. The panicle is rather open, with long ascending lower branches and shorter, slender, upper ones bearing a loose head of flowers. The rachis is slightly flexuose, usually green, pubescent, with numerous patent yellow prickles.
Flowers are c.2.5cm across with pure white broadly elliptical petals, 13 x 8mm or smaller. Styles are pale, whitish yellow; stamens are much longer than the styles; carpels glabrous, receptacle hairy. Sepals are moderatly thickly pubescent (some shiny green showing through), indistinctly white-edged, usually with long, fine points; patent at flowering.
The terminal leaflet is ovate to broadly elliptical with a poorly differentiated apex. The margins are irregularly sharply toothed. There are often only three leaflets, or sometimes three with two fused basal ones, or five separate leaflets.
The leaf underside is pubescent at first, becoming thinly hairy or nearly glabrous, giving a pale green appearance.
Stems often grow completely erect and are usually bright yellowish green (brownish in full sun). They are sparsely hairy but well developed ones are almost glabrous and shining and have striking yellowish prickles which are patent to slightly declining; some slightly curved upwards at the tip. They are somewhat flattened as the scientific name implies. The pale green striations on the stem seem to be more noticeable on this species than on most other brambles.