Rubus durotrigum – Series Hystrices

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This distinctive bramble is a British endemic, confined mainly to south-east Dorset. These photographs were taken of plants in a colony near Studland on the Isle of Purbeck in 2016 and 2021. Its main features are the pale pink to white flowers, light green leaves with large leaflets and a strongly glandular, hairless stem.

Rubus durotrigum is low-arching or prostrate in habit, but also grows up through other brambles or scrub. The panicle is pyramidal with the main head of flowers having short, stout, near-patent branches and a few much longer, ascending ones below; either flattish or rounded at the apex.

The dark reddish or purple slightly flexuose rachis and floral branches are densely clothed with fine straight prickles and acicles of varying sizes and abundant stalked glands, much like the stem, but also have numerous simple or stellate hairs.

Flowers are about 2.5cm in diameter with small, narrowly elliptical pale pink petals c.12 x 6mm (quickly fading to white in direct sunlight). Stamens are short, i.e. about equal to the height of the styles, white, with glabrous anthers. Styles are pale yellow, tinged reddish below; carpels glabrous, receptacle hairy.

The sepals have long, sharp-tipped or leafy points, which are patent to loosely reflexed on flowering, but then become erect and sometimes contorted after the petals have dropped. They have dense pubescence with short glands and acicles, and may appear thinly pale-bordered.

Leaves may have three or five contiguous to slightly imbricate leaflets, or three with one or both of the basal ones fused to the laterals. Leaflets are mid to light yellowish-green in colour, sometimes with a bronzy tinge. The terminal leaflet is large, c.11 x 8cm, often slightly convex and drooping. It is broadly ovate to nearly round, with an acuminate apex and emarginate to subcordate base. The margin is flat with relatively broad, acute, uneven teeth (somewhat incised).

Possibly a younger leaf with bronzy tinge and incised dentation:

Leaflets are unfelted below with sparse, short hairs giving a thin, hard texture.

The first-year stem is dark reddish-purple to blackish purple, bluntly angled with flat or slightly furrowed sides. It is virtually glabrous but has numerous fine, straight, declining, broad-based or narrow-based prickles chiefly on the angles, which are shorter to or about the same length as the width of the stem. There are also abundant fine pricklets of varying length all round the stem, which are often gland-tipped, in addition to some acicles and short-stalked glands. The prickles and pricklets have the base the same colour as the stem, often with a slightly redder middle portion and a yellow contrasting tip. Younger stems may be partially green.