Spiraea alba
Spiraea lucida
eastern, narrow-leaf, spirée blanche, white meadowsweet
birch-leaf spirea, shiny-leaf meadowsweet, shiny-leaf spiraea, shinyleaf spirea
erect, unbranched.
erect to ascending, often dying to ground annually, rarely branched.
petiole 2–8 mm, puberulent or sparsely hairy;
blade narrowly lanceolate to oblanceolate or broadly oblanceolate to obovate, 2–9 × 0.5–3 cm, length 3–5 times width, chartaceous or membranous, base cuneate to rounded, margins finely to coarsely, sharply serrate to serrulate (sometimes doubly so on long shoot leaves), number of primary and secondary serrations 0.5–1.1 times number of secondary veins (excluding inter-secondary veins), venation pinnate craspedodromous, secondary veins not prominent, irregularly terminating in primary teeth, inter-secondary veins usually 8–12+ per leaf, apex acute to obtuse, abaxial surface mostly glabrous, adaxial glabrous.
petiole 4–15 mm;
blade obovate to ovate, 2–8 × 1–3(–5) cm, membranous, base acute, margins usually coarsely serrate in distal 1/4–1/2 with secondary and tertiary teeth, teeth rounded or nearly entire with 1–2 teeth near apex, number of primary and secondary serrations 0–1 times number of secondary veins (excluding inter-secondary veins), venation pinnate cladodromous, secondary veins not prominent, apex acute to obtuse, surfaces glabrous.
mostly terminal, narrowly conic to open, pyramidal panicles, 5–20 × 3–10 cm height 1.4–3.5 times diam.;
branches usually in axils of leaves, puberulent to pubescent.
mostly terminal, corymbiform, 5–8 × 3–10 cm height 0.5–1 times diam.;
branches rarely in axils of leaves, glabrous or sparsely pubescent.
1–2(–3) mm, glabrous or glabrate.
0.5–4 mm, glabrous or sparsely pubescent.
3–8 mm diam.;
hypanthia hemispheric, 0.6–0.8 mm, abaxial surface usually puberulent to sparsely strigose, sometimes glabrate or glabrous, adaxial glabrous;
sepals triangular, 0.8–1.5 mm;
petals usually white, sometimes pink-tinged (in bud), suborbiculate, 1.3–2(–3) mm;
staminodes 0–4;
stamens 30–50, 1–2 times petal length.
4–6 mm diam.;
hypanthia hemispheric, 0.5–1 mm, abaxial surface glabrous, adaxial glabrous or glabrate;
sepals triangular, 0.5–1.1 mm;
petals white, orbiculate, 1–2 mm;
staminodes 10–12;
stamens 18–24, 2 times petal length.
oblanceoloid, 3–4 mm, shiny, glabrous.
oblanceoloid to ellipsoid, 2–2.5 mm, glabrous or sparsely pubescent.
Spiraea alba
Spiraea lucida
Varieties 2 (2 in the flora).
Varieties alba and latifolia have regions of hybridization, primarily around the Great Lakes, that produce intermediate forms that may be difficult to key. Recognition of these two taxa as either species or varieties has been problematic because the taxa are quite distinct at the extremes of their range. A. R. Kugel (1958) recognized them as distinct species and her work illustrates the regional zone of hybridization. H. A. Gleason (1952) and Gleason and A. Cronquist (1963) also recognized the two taxa as separate species; later Gleason and Cronquist (1991) recognized them as varieties that frequently intergrade.
The European Spiraea salicifolia has a leaf morphology that is similar to that of var. alba and the two taxa have been treated as conspecific. With the interest in Spiraea as an ornamental, S. salicifolia was imported to North America, resulting in this species or hybrids of it becoming naturalized. Specimens that are difficult to identify may be S. salicifolia, as escapes from homesteads and gardens that became established or may have hybridized with native taxa.
Spiraea alba has become locally naturalized in western and central Europe; in the British Isles, its hybrids are commonly naturalized as S. ×rosalba Dippel (S. alba × S. salicifolia), or as S. ×billardii Hortus ex K. Koch (S. alba × S. douglasii) (A. J. Silverside 1990).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Spiraea lucida has been considered a variety of S. betulifolia based upon: hypanthial vestiture, inflorescence shape, extent of leaf serration, and leaf texture (L. J. Uttal 1974); or, corymbiform inflorescences, white petals, plant nearly glabrous throughout (C. L. Hitchcock et al. 1955–1969, vol. 3; H. J. Scoggan 1978–1979, part 3; A. Cronquist et al. 1997). Although these character states occur in the eastern Asian S. betulifolia, it has very different leaf architecture showing much greater organization of the tertiary venation, which appears to be unique and is not found in any North American taxa. Spiraea lucida has an extremely variable leaf morphology that seems related to the tendency for stems to die back annually and the consequent annual production of long shoots. C. Sterling (1966) did not examine all taxa of Spiraea; the character states of carpel morphology of S. stevenii (see discussion there under) and S. lucida were reported to be similar and to differ slightly from those of S. betulifolia (the provenance of his specimen is not clear from the text).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves: lengths 3–4 times widths, margins finely serrate to serrulate; inflorescences narrowly conic. | var. alba |
1. Leaves: lengths 2–3 times widths, margins coarsely serrate; inflorescences open, pyramidal. | var. latifolia |
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