Herbs, perennial, 3–20 dm, self-compatible; rhizomatous, roots slender, fibrous, sometimes with thickened, ± fusiform or ± narrowly oblong tubers. Stems 1–5, ascending to erect. Leaves persistent or basal deciduous and cauline persistent, cauline (see discussion); stipules persistent, adnate to petiole, ± 1/2-ovate, margins dentate or deeply incised, rarely entire; petiole present; blade ± narrowly obovate to ± narrowly elliptic, 1.5–22 cm, herbaceous, major leaflets 3–19, leaflets along rachis in ± opposite pairs, minor leaflet pairs between each major pair 0–5, number usually increasing distally along rachis, major leaflet blades ovate, lanceolate, elliptic, rhombic, and/or obovate, minor leaflet blades ovate, elliptic, or obovate, margins flat, serrate to dentate, rarely incised, or in minor leaflet blades entire or few-toothed, eglandular hairs of two types: (1) soft and either straight or wavy (surfaces pilose, pubescent, or villous), and (2) stiff and straight (surfaces hirsute); glandular hairs of two types: (1) short-stipitate, and (2) sessile, both ± glistening (indumentum description applies to all plant surfaces in Agrimonia). Inflorescences terminal and often axillary, 9–120-flowered, simple or compound racemes (flexible); peduncles present; bracts present; bracteoles present. Pedicels present. Flowers 5–10 mm diam.; hypanthium stipitate, very short stipe adnate to hypanthium above bracteoles, reflexed at maturity, fruit abscising at base of stipe, hemispheric to obconic, becoming indurate, 0.5–2 mm, sulcate, throat occluded by annular disc, bristles in 2–5 circumferential rows from rim; sepals 5, spreading, ± ovate, 1–3 mm; petals 5, yellow, obovate to ± oval; stamens 5–15, shorter than petals; carpels 2, rarely more. Fruits achenes, 1 (1 ovary aborts), (including hypanthia) top-shaped, 1–6.6 mm; hypanthium persistent, enclosing achenes; sepals persistent, erect, connivent, bristles erect to reflexed, hooked. x = 7.
North America, Mexico, West Indies, Central America, South America, Eurasia, s Africa, circumboreal.
Species ca. 20 (7 in the flora).
Characters useful in separating Agrimonia species exhibit sufficient overlap of expressions among species, as well as variation within species, to confound identification. A suite of two or more characters is necessary to identify unequivocally any Agrimonia species. Because mature reflexed fruits, which provide the most consistent identifying characters, are frequently absent from material under examination, the key first presents the most useful vegetative characters. Hypanthium shape, size, indumentum, number of circumferential bristle rows, and position of the proximal row should be assessed on fully reflexed mature fruits. When mature fruits are not present, the hypanthium indumentum and number of bristle rows may be useful. Mid cauline leaves were selected to measure stipule shape, major leaflet shape and number, and minor leaflet number for comparison among the species, because most of those leaf characters vary in some way along the stem of a plant. The number of minor, or smaller, leaflets on each side of the rachis between any two major, or larger, leaflets also varies, increasing distally. The number of leaflets in the distal interval (the maximum number per leaf) can help separate species, for example, A. gryposepala and A. rostellata. Species with flowers more or less subopposite along the inflorescence axis have flowering inflorescences that are more compact in appearance, especially in the flowering portion. Presence of tuberous roots can separate A. gryposepala from A. rostellata and is useful in confirming identification.
Examining plant surfaces to determine the types of eglandular and glandular hairs is necessary and most accurately done with a 10× lens; frequently, glistening, sessile-glandular hairs can be seen with the naked eye. Despite the overlap in descriptions of the density of surface hairs (for example, sparsely versus scattered hirsute), these distinctions more completely describe the variation among species and between plant surfaces than merely describing them as hirsute.
No basal leaves occur in North American species of Agrimonia; before dormancy, a short section of stem is produced; it has the appearance of a basal rosette. The stem continues to elongate from that section in the spring.
|1||Stems with glistening glandular hairs (short-stipitate, sometimes also sessile) and ± hirsute||> 2|
|1||Stems with glandular hairs sometimes glistening (short-stipitate and sessile) and pubescent to villous and hirsute||> 3|
|2||Inflorescence axes ± ascending-hirsute (hairs 0.5–1 mm); minor leaflets 0–1(–2) pairs; roots with fusiform tubers; fruiting hypanthia hemispheric, 1–3.1 mm.||Agrimonia rostellata|
|2||Inflorescence axes hirsute (hairs 2 mm); minor leaflets 1–4, rarely 0–1, pairs; roots without tubers; fruiting hypanthia turbinate to broadly campanulate, rarely broadly obconic, 2.3–5.8 mm.||Agrimonia gryposepala|
|3||Abaxial leaflet surfaces (at 10\x) rarely glistening with sessile-glandular hairs||> 4|
|3||Abaxial leaflet surfaces (at 10\x, often with naked eye) glistening with sessile-glandular hairs||> 5|
|4||Stem hairs 3–4 mm; mid cauline stipules deeply incised; minor leaflets 0 or 1 pair; fruiting hypanthia 2.2–4 × 3–4.6 mm, ridges rarely sparsely hirsute.||Agrimonia microcarpa|
|4||Stem hairs 2–3 mm; mid cauline stipules dentate (but not deeply so); minor leaflets 1 or 1–3 pairs; fruiting hypanthia 1.9–4.5 × 2–4.6 mm, ridges sparsely hirsute.||Agrimonia pubescens|
|5||Major leaflets 5–7 on mid cauline leaves; mid cauline stipules proximally dentate or entire.||Agrimonia striata|
|5||Major leaflets 9–13 on mid cauline leaves; mid cauline stipules dentate||> 6|
|6||Major leaflet blades lanceolate to narrowly elliptic, rarely narrowly rhombic, margins serrate to dentate, apices acuminate or long-acuminate, rarely acute; flowers usually ± subopposite.||Agrimonia parviflora|
|6||Major leaflet blades ± obovate, margins incised, apices obtuse to acute; flowers usually ± alternate.||Agrimonia incisa|