Geum macrophyllum
Geum laciniatum
benoîte à grandes feuilles, bigleaf avens, large-leaf avens
benoîte lacinicée, floodplain avens, hairy herb-bennet, rough avens
30–110 cm, puberulent and hirsute or sparsely hirsute.
30–100 cm, hirsute, some hairs 2–2.5 mm.
basal 10–45 cm, blade interruptedly lyrate-pinnate, major leaflets 5–9, alternating with 4–15 minor ones, terminal leaflet usually much larger than major laterals;
cauline 2–12 cm, stipules ± free, 7–23 × 3–12 mm, blade lyrate-pinnate, pinnate, 3-foliolate, or simple and 3-lobed.
basal 15–32 cm, blade simple, lyrate-pinnate, or pinnate, major leaflets 1–7, alternating with 0–10 minor leaflets, terminal leaflet slightly to much larger than major laterals;
cauline 3.5–18 cm, stipules ± free, 4–14 × 7–17 mm, blade pinnate, 3-foliolate, or simple and unlobed.
3–16-flowered.
2–9-flowered.
densely puberulent, sometimes with scattered longer hairs, sometimes stipitate-glandular.
densely puberulent, hirsute, eglandular.
erect;
epicalyx bractlets often absent, 0.5–2 mm;
hypanthium green;
sepals erect-spreading but soon reflexed, 2.5–5.5 mm;
petals spreading, yellow, obovate, broadly elliptic, or suborbiculate, 3.5–7 mm, longer than sepals, apex rounded.
erect;
epicalyx bractlets 1–2 mm;
hypanthium green;
sepals spreading but soon reflexed, 3–10 mm;
petals spreading, white, oblong to elliptic, 2–5 mm, shorter than sepals, apex obtuse to rounded.
sessile or on less than 1 mm stipes, puberulent.
sessile, glabrous except for ring of bristles at base and tuft at apex.
geniculate-jointed, proximal segment persistent, 2.5–6 mm, apex hooked, sparsely to densely stipitate-glandular, distal segment deciduous, 1–2 mm, pilose in basal 1/3, hairs much longer than diam. of style.
geniculate-jointed, proximal segment persistent, 2.5–5 mm, apex hooked, glabrous, sometimes 1–2 eglandular bristles at base, distal segment deciduous, 1–2 mm, short hairs on basal 1/2.
= 42.
Geum macrophyllum
Geum laciniatum
Varieties 2 (2 in the flora).
Characters useful in recognizing specimens of Geum macrophyllum are yellow petals, epicalyx bractlets often absent, proximal style segment sparsely to densely stipitate-glandular, and fruiting receptacles puberulent. Across its broad North American range from Alaska to California and Nova Scotia, G. macrophyllum exhibits considerable variation. Based largely on the shape of the terminal leaflet of the basal leaves and the degree of dissection and shape of the divisions of the distal cauline leaves, P. A. Rydberg (1913b) distinguished three species within the range of variation treated here as one species. Basal leaves of G. macrophyllum in the strict sense (var. macrophyllum in this treatment) have relatively large reniform to rounded terminal leaflets and the distal cauline leaves are three-cleft into rhombic or cuneate lobes. The basal-leaf terminal leaflets of G. perincisum (= var. perincisum) are only slightly larger than the laterals and are deeply lobed into rhombic-obovate segments; the distal cauline leaves are dissected into oblanceolate divisions. Both basal and cauline leaves of G. oregonense (= var. perincisum) are intermediate between those of G. macrophyllum and G. perincisum. W. Gajewski (1955) crossed all three taxa under discussion and examined leaf morphology and cytology of the F1 and F2 hybrids. He concluded that they were distinct but not yet completely separated species. Fairly well correlated with the more dissected leaves of G. oregonense and G. perincisum is the presence of minute stalked glands on the pedicels. The treatment here follows H. M. Raup (1931) in recognizing two varieties of G. macrophyllum based more on pedicel glandularity than leaf morphology.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
B. L. Robinson and M. L. Fernald (1908) and J. K. Small (1933) misapplied the name Geum virginianum to this species. As a consequence, older specimens of G. laciniatum are often labeled (and filed in herbaria) as G. virginianum.
Geum laciniatum is unique among members of the genus in having some of the heads of achenes pop off the stem and disperse as a unit. The heads disarticulate where the torus joins the hypanthium, leaving the hypanthium inverted at the tip of the stem.
Fernald described var. trichocarpum based on the presence of bristles on the summits of the achenes. Although this morphology occurs to the near exclusion of the glabrous one in the western part of the species range, it also occurs as far east as the Carolinas, Maine, New Jersey, and Virginia. The glabrous condition has a smaller range, and it is the prominent one in Nova Scotia, Kentucky, Maine, and Ohio. The two are well mixed in Quebec, New York, and Pennsylvania. Although they are easily distinguished (hairs absent versus present), they seem to have little phytogeographic significance, and presence of achene hairs is not correlated with any other characteristics. It appears to be a trivial variation.
Geum laciniatum hybridizes with G. urbanum (= G. ×macneillii J.-P. Bernard & R. Gauthier); see discussion under 15. G. urbanum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Pedicels not glandular-puberulent; cauline leaves with distal simple and 3-lobed (divided less than 3/4 to base), lobes rhombic-oblong. | var. macrophyllum |
1. Pedicels glandular-puberulent; cauline leaves with distal 3-foliolate or simple and 3-lobed (divided almost to base), lobes oblanceolate to obovate. | var. perincisum |
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