Flora of North America species comparison

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Aruncus dioicus

Rosaceae tribe Spiraeeae

bride's feathers, buck's-beard, goat's-beard, sylvan goatsbeard
Habit Shrubs, subshrubs, or herbs, perennial (Aruncus); unarmed.
Leaves

leaflets green to gray-green, 6–15 cm, base subcordate to attenuate, apex acute to long-acuminate.

alternate, simple or pinnately compound;

stipules absent;

venation pinnate, sometimes palmate.
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.

perianth and androecium perigynous;

epicalyx bractlets absent or present;

hypanthium shallowly bowl-shaped, hemispheric, campanulate, patelliform, +/- crateriform, or turbinate;

torus absent, minute, or thickened;

carpels 3–5(or 6)[–8], distinct, free or adnate to hypanthium base, styles +/- terminal, distinct;

ovules 2–5, apical, collateral or clustered.
Fruits

aggregated follicles or achenes (Holodiscus);

styles deciduous or persistent, not elongate.
Seeds

1.5–2(–2.5) mm.

Aruncus dioicus

Rosaceae tribe Spiraeeae
Distribution
from FNA
AK; AL; AR; CA; CT; DE; GA; IA; IL; IN; KY; MD; ME; MI; MO; MS; NC; NJ; NY; OH; OK; OR; PA; SC; TN; VA; WA; WI; WV; AB; BC; NS; ON; QC; YT; Eurasia
[WildflowerSearch map]
[BONAP county map]
North America; Mexico; Central America; South America; Eurasia [Introduced widely]
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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera 8, species ca. 130 (6 genera, 25 species, including 3 hybrids, in the flora).

The two genera not present in North America north of Mexico are the southeastern European-western Asian Sibiraea Maximowicz (five species) and the Mexican Xerospiraea J. Henrickson (one species).

The base chromosome number for Spiraeeae is x = 9.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
var. dioicus
2. Follicles 1.6–2.4 mm; leaf surfaces densely hairy; w of Appalachians.
var. pubescens
3. Follicles 2.5–5 mm; Alaska and Yukon to n California.
var. acuminatus
3. Follicles 2.5–3 mm; introduced, ne United States.
var. vulgaris
1. Herbs, perennial; flowers unisexual; hypanthia shallowly bowl-shaped.
Aruncus
1. Shrubs or subshrubs; flowers bisexual; hypanthia hemispheric, campanulate, patelliform, +/- crateriform, or turbinate
→ 2
2. Subshrubs; leaves 2–3(–5)-ternate, primarily crowded basally.
Luetkea
2. Shrubs; leaves simple, cauline (tightly clustered in Petrophytum)
→ 3
3. Leaves deciduous, herbaceous, membranous, chartaceous, rarely coriaceous; stems erect, arching, or ascending, sometimes spreading to prostrate in Spiraea
→ 4
3. Leaves persistent, often marcescent, coriaceous; stems prostrate (mat-forming), sometimes ascending or erect in Petrophytum
→ 5
4. Fruits aggregated follicles; inflorescences panicles or corymbiform or racemiform; carpels free; petals greenish, yellowish, white, pink, or purple.
Spiraea
4. Fruits aggregated achenes; inflorescences panicles; carpels adnate to hypanthium base; petals usually white, sometimes pink tinged, rarely pink.
Holodiscus
5. Inflorescences panicles; petals white; stamens 20–40.
Petrophytum
5. Inflorescences: flowers solitary; petals pink to pinkish, often purple tinged; stamens 7–12.
Kelseya
Source FNA vol. 9, p. 423. FNA vol. 9, p. 398. Author: Luc Brouillet.
Parent taxa Rosaceae > subfam. Amygdaloideae > tribe Spiraeeae > Aruncus Rosaceae > subfam. Amygdaloideae
Subordinate taxa
A. dioicus var. acuminatus, A. dioicus var. dioicus, A. dioicus var. pubescens, A. dioicus var. vulgaris
Aruncus, Holodiscus, Kelseya, Luetkea, Petrophytum, Spiraea
Synonyms Actaea dioica
Name authority (Walter) Fernald: Rhodora 41: 423. (1939) de Candolle: in A. P de Candolle and A. L. P. P. de Candolle, in A. Pde Candolle and A. L. P. P. de Candolle, Prodr. 2: 541. (1825)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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