Spiraea alba Du Roi
CC = 9
CW = -3
MOC = 8
SRank = S1
Family - Rosaceae
Habit - Shrub to 2.0 m.
Stems - Ascending or erect. Twigs reddish brown to grayish brown with prominent, small lenticels, somewhat angular, minutely hairy toward the tip when young, glabrous or nearly so at maturity.
Leaves - Alternate, simple, mostly short-petiolate. Blades 3-6 cm long, somewhat stiff textured, narrowly elliptic to oblanceolate, angled or tapered at the base, angled or tapered to a sharply pointed tip, the margins finely and sharply toothed, the surfaces glabrous or nearly so.
Inflorescences - Terminal panicles of numerous flowers, longer than wide, cylindrical or ovoid to more or less pyramididal, sometimes elongate.
Flowers - Hypanthia 1.5-2.0 mm wide, cup-shaped, glabrous or minutely hairy. Sepals 5, 1.0-1.5 mm long, triangular, bluntly pointed at the tip. Corollas of 5 petals, not doubled, these 2.7-3.5 mm long, white. Stamens 15 to numerous, the anthers white or pink. Pistils 5 (except in doubled flowers), free. Ovary superior, glabrous, with 1 locule and 2 to several ovules. Style 1 per pistil, persistent, the stigma more or less capitate.
Fruits - Follicles 3.0-3.5 mm long, ascending, elliptic-ovate in outline, tapered to an erect beak at the tip, glabrous, tan to brown at maturity, dehiscing along the inner suture and also partially along the outer (dorsal) suture, 1-4-seeded. Seeds 1.5-2.5 mm long, narrowly ellipsoid, the surface with faint longitudinal lines or a fine network of slender ridges and quadrangular pits, yellowish to reddish brown.
Flowering - June - August.
Habitat - Bottomland prairies, marshes, lake margins, edges of bottomland forests, ditches, fencerows, railroads, and roadsides.
Origin - Native to the U.S.
Lookalikes - None close.
Other info. - This species is uncommon in Missouri, reported from only a few widely scattered counties. Its main range is predominantly north and northeast of Missouri, and extending into much of Canada. Flowering plants are readily identified by their spikes of small white flowers which bear numerous stamens. The erect follicles of fruiting plants are also distinctive. The leaves are alternate, roughly elliptic, and somewhat stiff.
Photographs taken near Loda Lake, Newaygo County, MI, 8-27-2020 (SRTurner).