Aruncus dioicus

(Walter) Fernald

Rhodora 41: 423. 1939.

Illustrated
Basionym: Actaea dioica Walter Fl. Carol., 152. 1788
Treatment appears in FNA Volume 9. Treatment on page 423. Mentioned on page 424.

Leaves: leaflets green to gray-green, 6–15 cm, base subcordate to attenuate, apex acute to long-acuminate. Flowers: sepals 1 mm; petals 0.5–1.5 mm, apex acute to obtuse; stamens 1.5–2 mm, filaments slender, ± equal, anthers versatile; styles [0.2–] 0.3–0.8 mm. Seeds 1.5–2 (–2.5) mm.

Distribution

V9 713-distribution-map.jpg

Alta., B.C., N.S., Ont., Que., Yukon, Ala., Alaska, Ark., Calif., Conn., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mich., Miss., Mo., N.C., N.J., N.Y., Ohio, Okla., Oreg., Pa., S.C., Tenn., Va., W.Va., Wash., Wis., Eurasia

Discussion

Varieties 14 (4 in the flora).

Aruncus dioicus is superficially similar to Astilbe biternata (Saxifragaceae), false goat’s-beard, which is endemic to the southern Appalachian Mountains. Both species produce tall, dioecious plants with biternately to bipinnately compound leaves and plumelike terminal panicles with many, relatively small white, unisexual flowers, and may grow side by side. Aruncus dioicus is more widespread and may be readily distinguished by its unlobed rather than 3-lobed terminal leaflets, flowers with 20 rather than 10 stamens, and 3 carpels reflexed in fruit rather than 2 erect carpels. See T. L. Mellichamp (1976) for an analysis of this remarkable example of convergent evolution.

Aruncus dioicus is striking and is grown in gardens throughout North America. It is variable throughout the temperate and subarctic regions of the Northern Hemisphere, especially in China and Japan. H. Hara (1955) recognized the following varieties that are found in the flora area.

Selected References

None.

Key

1 Follicles 1.5–2.4 mm; styles 0.3–0.8 mm; seeds 1.5–2 mm > 2
1 Follicles 2.5–5 mm; styles 0.3–0.5 mm; seeds 1.8–2.5 mm > 3
2 Follicles 1.5–2 mm; leaf surfaces glabrous or slightly hairy; s Appalachians and eastward. Aruncus dioicus var. dioicus
2 Follicles 1.6–2.4 mm; leaf surfaces densely hairy; w of Appalachians. Aruncus dioicus var. pubescens
3 Follicles 2.5–5 mm; Alaska and Yukon to n California. Aruncus dioicus var. acuminatus
3 Follicles 2.5–3 mm; introduced, ne United States. Aruncus dioicus var. vulgaris

"thick" is not a number.

... more about "Aruncus dioicus"
T. Lawrence Mellichamp +
(Walter) Fernald +
compound +  and simple +
opposite +  and alternate +
subcordate +  and attenuate +
Actaea dioica +
reduced +
15 cm150 mm <br />0.15 m <br /> (60 cm600 mm <br />0.6 m <br />) +
thick +  and thin +
2-3-irregularly ternate +  and odd-pinnate +
Alta. +, B.C. +, N.S. +, Ont. +, Que. +, Yukon +, Ala. +, Alaska +, Ark. +, Calif. +, Conn. +, Del. +, Ga. +, Ill. +, Ind. +, Iowa +, Ky. +, Maine +, Md. +, Mich. +, Miss. +, Mo. +, N.C. +, N.J. +, N.Y. +, Ohio +, Okla. +, Oreg. +, Pa. +, S.C. +, Tenn. +, Va. +, W.Va. +, Wash. +, Wis. +  and Eurasia +
not +  and aggregated +
0.3 cm3 mm <br />0.003 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
retrorse +  and inverted +
ovate-elongate +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
not +  and aggregated +
not +  and aggregated +
rhizomatous +, glandular +, multicellular +  and simple +
straight +  and curved +
glabrous or +  and sparsely densely hairy +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
500-2500-flowered +
crassinucellate +
compound +  and simple +
deciduous +
long-petiolulate +
green +  and gray-green +
broadly ovate +  and narrowly lanceolate +
6 cm60 mm <br />0.06 m <br /> (15 cm150 mm <br />0.15 m <br />) +
entire +, pinnate +  and serrate +
toothed +, unlobed +  and lobed +
inferior +  and superior +
biseriate +  and clustered +
collateral +  and apical +
2 +  and 4 +
0 (?) +  and 4 (?) +
free +  and distinct +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
adnate +, free +, connate +  and distinct +
not arillate +
0.2 cm2 mm <br />0.002 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
caudate;elongate +
1.5mm +  and 2mm +
membranous +
persistent +
free +  and distinct +
spreading +  and appressed +
triangular +
1 cm10 mm <br />0.01 m <br /> (?) +
Illustrated +
free +  and distinct +
rudimentary +
1.5mm +  and 2mm +
1 +  and 5 +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.03 cm0.3 mm <br />3.0e-4 m <br />) +
persistent +
distinct +
basal +, lateral +, subterminal +  and terminal +
not elongate +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.08 cm0.8 mm <br />8.0e-4 m <br />) +
Aruncus dioicus +
species +
inconspicuous +
pistillate +  and staminate +
herb +  and clump-forming +