A deciduous dwarf or prostrate shrub reaching when old 6 to 10 in. in height, usually dwarfer; young shoots downy, distinctly grooved, becoming spine-tipped with age. Leaves alternate, simple, very tiny (about 1⁄4 in. long), linear, hairy, soon falling. Flowers 3⁄8 in. long, pale yellow, solitary in the terminal leaf-axils or in clusters of two to four, each on a downy stalk 1⁄8 to 1⁄4 in. long. Corolla of the normal broom-flower shape. Calyx downy, 3⁄16 in. long,with narrowly triangular lobes. Pod 5⁄8 in. long, 1⁄3 in. wide, pointed, downy. Blossoms in June.
Native of S. France and S. Spain. This interesting dwarf shrub is charming for a sunny spot in the rock garden. A plant grew at Kew for many years and proved perfectly hardy there. Planted above a stone, it had draped itself over it and formed a pendulous mass of spine-tipped twigs 18 in. in diameter and about 3 in. in thickness. It needs the sunniest possible position. G. horrida has similar spine-tipped twigs, but its leaves are opposite, and Erinacea anthyllis, similarly spiny, has purplish-blue flowers.
G. lobelii is one of a number of very closely allied genistas of the Mediterranean region which are exceedingly difficult to discriminate, varying as they do in their basic differential characters. Of these, G. salzmannii DC., native of Corsica, Sardinia, etc., differs chiefly in habit. For in G. lobelii the branches are short and sinuous, and bear numerous short, spine-tipped branchlets crowded into a tuft or dome, while in G. salzmannii the branches are straighter, with the branchlets and flowers arranged all along them. In both species the flowers may be solitary or clustered. The genista of S. Spain known by the illegitimate name G. baetica Spach is also closely allied to G. lobelii. These three species are scarcely separable from G. aspalathoides Lam., described from Tunisia.