14. Geum L. (avens)

Plants perennial herbs, lacking spines and thorns, with short erect rootstocks or rhizomes. Stems erect or ascending, sometimes somewhat arched. Leaves alternate and basal (all basal in G. fragarioides, opposite in G. triflorum), sometimes entire, ternately, and/or pinnately compound, in some species the most divided leaves often with smaller leaflets interspersed with the larger primary ones, short- to long-petiolate, the leaf blade broadly ovate, triangular, or kidney-shaped to lanceolate or oblanceolate in overall outline, the leaflets with the margins finely to coarsely toothed and often also lobed. Stipules herbaceous, those of the basal leaves fused to the petiole, those of the stem leaves free and more or less leaflike, elliptic-lanceolate to broadly and asymmetrically ovate, rounded or narrowed at the base, the outer margin often with few to several lobes and also toothed. Inflorescences terminal, solitary or more commonly few-flowered, open, branched clusters or panicles, the flowers stalks mostly relatively long, the branch points usually with a stipulelike bract, the stalks often also with a pair of reduced stipulelike bracts near the midpoint. Flowers ascending or drooping, perigynous, the hypanthium deeply cup-shaped to bell-shaped, sometimes appearing obconic, with a more or less well-developed nectar disc along the rim, each flower (except in G. fragarioides and G. vernum) with 5 bractlets alternating with the sepals (the calyx thus appearing more or less 10-parted), these 1–3 mm long, inconspicuous, linear to narrowly oblong, not becoming enlarged at fruiting. Sepals 5, loosely ascending to spreading or reflexed at flowering, usually reflexed at fruiting. Petals 5, narrowly to broadly elliptic, white, cream-colored, or yellow (pink to pinkish purple in G. triflorum). Stamens (10–)20 to numerous, the anthers yellow. Pistils numerous, densely covering the surface of the more or less spherical to short-columnar receptacle, this glabrous or hairy. Ovaries superior, not hidden in the hypanthium, with 1 ovule. Style 1 per ovary, terminal, noticeably jointed at the base (in G. fragarioides) or above the midpoint (not noticeably jointed in G. triflorum), in the jointed species the 2 portions dissimilar, the apical segment shed as the fruit matures, the basal segment (absent in G. fragarioides) hooked at the tip and becoming elongated, persistent at fruiting. Stigma minute. Fruits achenes, free from and not hidden by the hypanthium (mostly hidden in G. fragarioides), densely covering the receptacle (sometimes few in G. fragarioides) and forming a globose to obovoid mass, the main body asymmetrically elliptic to ovate or obovate in outline, sometimes narrowly so, somewhat flattened, tapered abruptly to the hardened style at the tip (except in G. fragarioides). About 50 species, North America, South America, Europe, Asia, Africa, New Zealand, Tasmania, Auckland Islands.

The persistent, hooked basal portions of the styles in most species of Geum are an adaption to dispersal of the fruits in the fur (or clothing) of passing mammals. In the spring, the first leaves of the basal rosette produced in all species (except G. fragarioides) usually are simple and entire, with subsequent basal leaves progressively more divided.

Rydberg (1908–1918) reported two additional species, G. aleppicum Jacq. (yellow avens, as G. strictum Aiton, an illegitimate name) and G. rivale L. (water avens, purple avens), as occurring in Missouri, but because his treatment did not include specimen citations it has not been possible to account for these conclusively. As far as can be determined from examination of older specimens, his reports were based on misdetermined specimens. Both of these widespread species otherwise occur only to the north of Missouri in the midwestern portion of their ranges.