Sorbus aucuparia
Sorbus americana
European mountain-ash, rowan, rowan-berry, sorbier des oiseaux, sorbier des oiseleurs
American mountain-ash, sorbier d'amérique
1–3(or 4);
bark gray to bronze;
winter buds purple, ovoid to ovoid-conic, 5–15 mm, dull, not glutinous, usually densely villous, hairs whitish, rarely rufous, outer scales sometimes merely ciliate.
1–4+;
bark gray to bronze;
winter buds green to purple, shiny, ovoid to conic, 7–20 mm, glutinous, glabrous or hairy along scale margins and at apex, hairs primarily rufous.
pinnately compound;
stipules deciduous or persistent, whitish-villous or glabrate;
blade paler or often whitish abaxially, dull green to bluish green adaxially, leaflets 11–17(–19), opposite, oblong to oblong-lanceolate or oblanceolate, (2.5–)3–6(–7.5) × 1.5–2 cm, l/w ratio 2.4–3.7, margins serrate at least in distal 1/2, often almost to base, apex acute to obtuse, abaxial surface white-tomentose to villous at flowering, indument often persisting, at least along midveins, leaflet axils, and petiole bases, hairs usually whitish, sometimes rufous.
pinnately compound;
stipules early deciduous, rufous-ciliate, margins sometimes glandular;
blade paler abaxially, dull green to yellowish green adaxially, leaflets 11–17, opposite, lanceolate to oblong-lanceolate, 5–10 × 1–2.5 cm, l/w ratio 3.4–5, margins serrulate to serrate, at least in apical 1/2 and often almost to base, apex acuminate to long acuminate, surfaces glabrous or glabrate at flowering, some hairs occasionally persisting abaxially along midvein;
leaflet axils and petiole bases glabrous or with rufous and/or whitish hairs adaxially.
75–200+-flowered, flat-topped or rounded, 6–18 cm diam.;
peduncles ± whitish-villous.
125–400+-flowered, flat-topped or rounded, 6–15 cm diam.;
peduncles glabrous or sparsely villous.
densely whitish-villous.
glabrous or sparsely villous.
8–11 mm diam.;
hypanthium densely villous, hairs whitish, hypanthium plus sepals 2.9–3.2 mm;
sepals 0.5–1 mm, margins often glandular;
petals white, orbiculate, (3–)4–5 mm;
stamens 15–20;
carpels 1/2 adnate to hypanthium, apex conic, styles 3 or 4, 1.5–3 mm.
5–7.5(–8.5) mm diam.;
hypanthium glabrous, hypanthium plus sepals 2–2.5 mm;
sepals 0.5–1 mm, margins entire, often with a few thick glands;
petals white, orbiculate to obovate, (2–)2.5–3.5(–4) mm;
stamens 14–20;
carpels 1/2 adnate to hypanthium, apex conic, styles 3 or 4, 1.5–2 mm.
glabrous or densely villous.
glabrous or sparsely villous.
yellow or orange-red to red, globose to subglobose, 8–12 mm diam., shiny or dull, slightly glaucous or not;
sepals inconspicuous, incurved.
bright red to orange-red, globose to subglobose, 4–7 mm diam., shiny, not glaucous;
sepals inconspicuous, incurved.
brown, ovoid to ovoid-lanceoloid, 3–4.5 × 1.5–2 mm, asymmetric, slightly flattened.
brown, yellowish when fresh or immature, ovoid to ovoid-lanceoloid, 2.5–3.3 × 1.5–2 mm, asymmetric, slightly flattened.
= 34.
= 34.
Sorbus aucuparia
Sorbus americana
Sorbus aucuparia is a commonly planted ornamental tree that is widely bird-disseminated. The species is often confused with S. decora, from which it differs by its ovoid and usually densely whitish-villous and nonglutinous winter buds and by its densely villous flowering pedicels and hypanthia. The leaflets of S. aucuparia are often tomentose abaxially at flowering; those of S. decora are glabrous or sparsely villous. Examination of leaflet serration is also useful; S. decora exhibits a prolonged apical tooth; it is no longer than the lateral ones in S. aucuparia. The lateral teeth are relatively finer and sharper in S. decora compared to those of S. aucuparia. At a magnification of at least 70× , leaflets of S. aucuparia are reportedly minutely papillose abaxially; those of S. decora are not papillose (H. A. McAllister 2005). Natural hybrids with S. decora have been reported by G. N. Jones (1939) (one fruiting specimen found near Opeongo Lake, Algonquin Park, Ontario), with Aronia arbutifolia [x\Sorbaronia hybrida (Moench) C. K. Schneider; synonyms A. hybrida (Moench) Zabel, Sorbus spuria Persoon] in Truro, Nova Scotia, and also in Maine, New Hampshire, and Vermont (D. W. Magee and H. A. Ahles 1999), and with A. melanocarpa (x\Sorbaronia fallax C. K. Schneider) in Maine and Massachusetts. Other nothospecies names for putative intergeneric hybrids involving S. aucuparia include: ×Crataegosorbus miczurinii Pojarkova (Crataegus sanguinea Pallas × S. aucuparia), and ×Sorbocotoneaster pozdnjakovii Pojarkova (Cotoneaster melanocarpus (Ledebour) Loddiges, G. Loddiges & W. Loddiges ex M. Roemer × S. aucuparia [as S. sibirica Hedlund]). Subspecies of Sorbus aucuparia were recognized by McAllister; the authors made no attempt to identify specimens infraspecifically. Sorbus subvestita Greene is variably considered to be a synonym of S. aucuparia (Jones) or S. decora (M. L. Fernald 1950; H. A. Gleason and A. Cronquist 1991). However, Jones explicitly cited the isotype of S. subvestita in his specimen citation for S. aucuparia along with an acknowledgement of the confusion with S. decora.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Sorbus americana reputedly flowers about one week earlier than S. decora. Some authors have described S. americana as having generally thinner leaflets relative to thicker and firmer ones for S. decora; examination of herbarium specimens appears to support this, though the authors made no systematic study of blade thickness. No confirmed putative hybrids with S. decora are reported, although hybridization may occur. The hybrid ×Sorbaronia jackii Rehder [Aronia ×prunifolia (Marshall) Rehder × S. americana; synonym Pyrus ×jackii (Rehder) Fernald] has been reported from New Brunswick as a fastigiate shrub 20 dm tall with leaves intermediate in appearance between the putative parents. Garden hybrids involving S. americana are occasionally cultivated in North America; none has been reported as escaped. These include: Sorbus ×splendida Hedlund (a hybrid with S. aucuparia), S. ×plantierensis Simon-Louis ex C. K. Schneider (with S. aria), ×Sorbaronia monstrosa (Zabel) C. K. Schneider (with A. arbutifolia), and ×Sorbaronia sorbifolia (Poiret) C. K. Schneider (with A. melanocarpa); synonyms of ×Sorbaronia sorbifolia include A. sargentii (Dippel) Zabel, A. watsoniana M. Roemer, and Pyrus ×mixta Fernald.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
