Spiraea corymbosa
Rosaceae tribe Spiraeeae
dwarf spiraea, shinyleaf meadowsweet
erect to arching, branched.
petiole 3–8 mm, sparsely hairy;
blade ovate to elliptic or suborbiculate, 2–10 × 1–2.5 cm, coriaceous, base obtuse, rounded, or subcordate, margins irregularly, coarsely and sharply doubly serrate from midpoint to apex, teeth acute and mucronate, number of primary and secondary serrations 1 times number of secondary veins (excluding inter-secondary veins), venation pinnate cladodromous, secondary veins not prominent, apex acute, obtuse, or rounded, abaxial surface mostly glabrous, adaxial glabrous.
alternate, simple or pinnately compound;
stipules absent;
venation pinnate, sometimes palmate.
mostly terminal, corymbiform, 2–5 × 3–10 cm height 0.4–1.1 times diam.;
branches rarely in axils of leaves, glabrous or glabrate.
1–3 mm, glabrous or glabrate.
4–7 mm diam.;
hypanthia hemispheric, 0.8–1 mm, abaxial surface glabrous or pubescent, adaxial glabrous;
sepals triangular, 0.5–1 mm;
petals chalky white to pink, orbiculate, 1.3–1.5 mm;
staminodes 5–15 reduced to serrations;
stamens 15–20, 2 times petal length.
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.
aggregated follicles or achenes (Holodiscus);
styles deciduous or persistent, not elongate.
nearly fusiform, 2–3 mm, shiny, glabrous.
= 36.
Spiraea corymbosa
Rosaceae tribe Spiraeeae
H. A. Gleason and A. Cronquist (1963) and L. J. Uttal (1974) considered Spiraea corymbosa to be a variety of S. betulifolia. K. Sax (1936) found S. corymbosa to be a triploid with complete pollen sterility and hypothesized that it must exist as a diploid, or form viable egg cells, because it is involved in hybrids. If so, these cytological differences may be correlated with some morphological variation.
(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.)
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 |
MD Biodiversity
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