Rubus L.
(C.J.W., D.R.G.)
Shrubs or subshrubs, sometimes perennial herbs, often suckering or layering; habit partially erect with arching or flexuous branches, or lianoid or scrambling; stems biennial or perennial, sometimes rooting at apices, usually armed with prickles or pricklets or both, sometimes densely tomentose or pilose, sometimes glandular. Lvs distributed along stems, alternate, petiolate, imparipinnate or palmate with 3-7 toothed or lobed leaflets, occasionally reduced to a single leaflet or simple and palmately lobed with coalescing leaflets; stipules free or adnate to petiole, small- to medium-sized, persistent or deciduous. Fls often in leafy racemes or panicles, or solitary, usually born on shoots of previous year's growth, usually 5-merous, usually ⚥, rarely unisexual, pedicellate, often showy. Hypanthium with a large, often convex carpophore. Epicalyx 0. Calyx of 5 sepals, sometimes conspicuous and leafy. Petals 5 or rarely more, white to pink or rarely yellowish or purple. Stamens numerous, rarely few, arising from hypanthium rim. Ovary superior; carpels usually numerous; styles usually deciduous; ovules 2 but 1 aborting. Fr. a fleshy aggregate of 1-seeded drupelets.
Key
c. 250 sexual spp. and over 2000 agamospp., cosmopolitan. Native spp. 5, naturalised 5 (with subgen. Rubus, R. fruticosus agg. and related spp., represented by 19 segregates and 1 common hybrid).
Rubus includes important small frs of commercial value in temperate regions, such as R. idaeus (raspberry), R. × loganobaccus (loganberry), and R. spectabilis (salmonberry). Other spp. are widespread and serious agricultural pests. Although the taxonomy of several subgenera does not pose particular problems (except that many spp. are still imperfectly known), subgen. Rubus is very problematic and hundreds of segregates are recognized in Europe alone - most belong to the aggregate sp. R. fruticosus L., the common blackberry. A consensus has yet to be arrived at regarding classification of this group. At one extreme, A. Löve has proposed division of subgen. Rubus in C. and N. Europe into 3 spp., with most forms falling into R. fruticosus [ Feddes Repert 63: 145 (1960)]. At the other extreme, some authors recognise, equally, all agamospp. Heslop-Harrison, Y., in Fl. Europ. 2 (1968), recognised 66 circle spp. for European members of subgen. Rubus with other specific entities being aggregated under these. However, Newton, A., Watsonia 13: 35-40 (1980), pointed out that it is not possible to draw the boundaries of such entities so tightly that all plants can be unequivocably assigned to them; many taxa will fit equally uncomfortably into more than one.
In this treatment, European, Asian and N. American members of subgen. Rubus are keyed to and described under R. fruticosus agg. This allows the agamospecies to be recognised individually, while preserving their collective affinities as the common blackberry.