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European mountain-ash, rowan, rowan-berry, sorbier des oiseaux, sorbier des oiseleurs

northern mountain-ash, showy mountain-ash, sorbier plaisant

Habit Trees, 60–150 dm. Shrubs or trees, 30–150 dm.
Stems

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 purplish at maturity, shiny, conic, 10–20 mm, glutinous, scales ciliate to moderately (densely) villous, hairs primarily rufous.

Leaves

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 deciduous, sometimes persistent, glabrous or with whitish and/or rufous hairs;

blade paler abaxially, dull green to bluish green adaxially, leaflets (11–)13–17, opposite, elliptic, oblong to oblong-ovate, 4–7(–8) × 1.5–2.5 cm, l/w ratio 2.4–3.2(–3.6), margins serrate, sometimes serrulate, at least in distal 1/2 and often almost to base, apex abruptly short-acuminate, cuspidate, acute, or obtuse, surfaces essentially glabrous or sparsely (moderately) villous at flowering, usually glabrescent thereafter, sometimes persistently villous along midveins abaxially;

leaflet axils and petiole bases glabrous or with some rufous and/or whitish hairs adaxially.

Panicles

75–200+-flowered, flat-topped or rounded, 6–18 cm diam.;

peduncles ± whitish-villous.

75–400+-flowered, flat-topped or rounded, 6–15 cm diam.;

peduncles sparsely to moderately (densely) villous.

Pedicels

densely whitish-villous.

sparsely to moderately (densely) villous.

Flowers

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.

(7–)8–12 mm diam.;

hypanthium glabrous or sparsely villous proximally, hairs whitish or rufous, hypanthium plus sepals 2.5–3.5 mm;

sepals 1–1.5(–2) mm, margins entire, often with a few thick glands;

petals white, orbiculate to obovate, (3–)3.5–5 mm;

stamens 15–20;

carpels 1/2 adnate to hypanthium, apex conic, styles 3 or 4, 1.5–2.5 mm.

Infructescences

glabrous or densely villous.

sparsely to moderately villous, rarely glabrous.

Pomes

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, globose to subglobose, (5–)7–11 mm diam., shiny or dull, often glaucous when dried;

sepals inconspicuous, incurved.

Seeds

brown, ovoid to ovoid-lanceoloid, 3–4.5 × 1.5–2 mm, asymmetric, slightly flattened.

brown, lanceoloid, 4.5–5 × 1.5–2 mm, slightly asymmetric, slightly flattened.

2n

= 34.

= 68.

Sorbus aucuparia

Sorbus decora

Phenology Flowering spring; fruiting fall. Flowering spring; fruiting fall.
Habitat Thickets, roadsides, woods, other habitats near towns, scattered in remote natural settings Moist or dry woods, montane woods, rocky slopes, lake and stream shores, thickets
Elevation 0–2100 m (0–6900 ft) 0–1300 m (0–4300 ft)
Distribution
from FNA
AK; CA; CO; CT; DC; IA; ID; IL; IN; MA; MD; ME; MI; MN; MT; ND; NE; NH; NJ; NY; OH; OR; PA; RI; SC; SD; UT; VT; WA; WI; WV; WY; AB; BC; NB; NF; NS; ON; PE; QC; SK; SPM; Eurasia; n Africa; Atlantic Islands (Iceland, Madeira) [Introduced in North America; introduced also in Pacific Islands (New Zealand)]
[WildflowerSearch map]
[BONAP county map]
from FNA
CT; IA; IL; IN; MA; ME; MI; MN; NH; NY; OH; PA; VT; WI; MB; NB; NL; NS; NU; ON; PE; QC; SK; SPM; Greenland
[WildflowerSearch map]
[BONAP county map]
Discussion

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 decora reputedly flowers about one week later than S. americana. The two are sometimes confused when one is not familiar with the smaller flowers and fruits, and the distinctly longer and notably acuminate leaflets of S. americana. Leaflet length/width ratios greater than 3.2 are sometimes observed on narrower leaflets of S. decora, and a range of representative leaflets need to be sampled before determination. Another species frequently confused with S. decora is S. aucuparia, characterized by ovoid, usually densely whitish-villous and not glutinous winter buds as well as densely villous flowering pedicels and hypanthia, and often abaxially tomentose leaflets at flowering. The teeth on margins of leaves in S. decora are more finely pointed and sharper than those of S. aucuparia, and the apical tooth is often distinctly prolonged in S. decora; it is no more conspicuous than the lateral ones in S. aucuparia (E. G. Voss 1972–1996, vol. 2). The leaflets of S. aucuparia are reported to be minutely papillose abaxially (visible at 100× ); those of S. decora and other members of sect. Commixtae are not papillose (H. A. McAllister 2005). Sorbus decora is reported to be extirpated from Indiana.

Chromosome counts of 2n = 34 were reported by Á. Löve and D. Löve (1965, 1982b) for Sorbus decora. Doubt exists about the identity of the material that they sampled, as the only voucher specimen retraced (Á. & D. Löve 6559, COLO, WIN), although only vegetative and juvenile, is nonetheless referable to S. aucuparia. These doubtful chromosome counts also formed the basis for the recognition of S. groenlandica (Löve and Löve 1965b), reputedly of Greenland, coastal Labrador, and alpine and subalpine regions of northeastern North America, which apparently differed from S. decora with a chromosome count of 2n = 68 (T. W. Böcher and K. Larsen 1950; K. Holmen in C. A. Jørgensen et al. 1958). Reliable S. decora chromosome counts by H. A. McAllister (2005) of three wild collections (Dundas, Ontario; St. Anne de Beaupré, Quebec; Narsarsuaq Greenland) and two of cultivated material rendered this proposition untenable with consistent counts of 2n = 68. Further, critical examination of herbarium specimens from Greenland yielded no consistent morphologic character to separate S. decora from S. groenlandica, though leaflet and fruit size in the latter tended to be relatively smaller.

A naturally occurring putative intergeneric hybrid, ×Sorbaronia arsenii (Britton ex L. Arsène) G. N. Jones, synonym Pyrus ×arsenii (Britton ex L. Arsène) L. Arsène [= Aronia ×prunifolia (Marshall) Rehder × Sorbus decora], is known from New Brunswick, Nova Scotia, Prince Edward Island, St. Pierre and Miquelon, Quebec, and, possibly, Newfoundland. The hybrid is a 10–25 dm shrub with finely serrulate, partially pinnate leaves containing (0 or)1–3 pairs of reduced, distinct leaflets proximally and a much larger, 1–3-lobed terminal segment. The midvein on the adaxial surface of the terminal leaflet may be irregularly glandular or eglandular. A possible variant of this hybrid (parentage unconfirmed), much closer to Sorbus in appearance, is found in southwestern Newfoundland. It possesses finely serrulate, almost fully pinnate leaves, often with four or five pairs of distinct leaflets, the distal first or second leaflet pairs more or less pinnatifid or partially fused to the terminal leaflet. The hypanthium and abaxial surface of the sepals are villous, the anthers are pink or red, and the pomes are usually red, though some are reported to be blackish in age, often with some tomentum persisting on the abaxial surface of the persistent sepals.

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

Source FNA vol. 9, p. 438. FNA vol. 9, p. 440.
Parent taxa Rosaceae > subfam. Amygdaloideae > tribe Maleae > Sorbus > subg. Sorbus > sect. Sorbus Rosaceae > subfam. Amygdaloideae > tribe Maleae > Sorbus > subg. Sorbus > sect. Commixtae
Sibling taxa
S. americana, S. californica, S. decora, S. hybrida, S. intermedia, S. sambucifolia, S. scopulina, S. sitchensis, S. torminalis
S. americana, S. aucuparia, S. californica, S. hybrida, S. intermedia, S. sambucifolia, S. scopulina, S. sitchensis, S. torminalis
Synonyms Pyrus aucuparia, S. subvestita Pyrus americana var. decora, P. decora, P. decora var. groenlandica, S. decora var. groenlandica, S. groenlandica
Name authority Linnaeus: Sp. Pl. 1: 477. (1753) (Sargent) C. K. Schneider: Bull. Herb. Boissier, sér. 2, 6: 313. (1906)
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