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1 Inflorescence a simple umbel; flowers white; [section Chamaedryon]; [alien]. |
..2 Flowers 10-15 mm in diameter. |
....3 Leaves 2-7 cm long, coarsely serrate and sometimes also slightly 3-lobed; inflorescences with > 6 flowers |
....3 Leaves 1-4 (-5) cm long, finely serrulate, not lobed; inflorescences with 3-6 flowers |
..2 Flowers 6-10 mm in diameter. |
......4 Leaf blades linear to lanceolate, 2.5-4 cm × 0.3-1 cm, > 4× as long as wide; flowers 6-8 mm in diameter |
......4 Leaf blades ovate to obovate, 3-5 cm × 2-3 cm, < 2× as long as wide; flowers 7-10 mm in diameter |
1 Inflorescence a compound corymb or panicle; flowers white, pink, or red; [native or alien]. |
........5 Inflorescence a corymb, flat-topped or rounded, broader than long; [section Calospyra]. |
..........6 Leaves rounded, obtuse, or acute at the apex; petals white (rarely pink); [native]. |
............ 7 Follicle 2-3 mm long; leaves 1-2× as long as wide, rounded or obtuse at apex, rounded at base; plants 3-8 (-10) dm tall; [of dry or moist forested slopes, or thin soil on rock outcrops, rarely of streambanks] |
............ 7 Follicle 1-2 mm long; leaves 2-4× as long as wide, acute at apex, cuneate at base; plants 4-25 dm tall; [of rocky riverbanks] |
..........6 Leaves long-acuminate at the apex; petals pink (rarely white or red); [alien]. |
............ ..8 Leaves glabrous; flowers usually white (rarely pink); shrub to 8 dm tall |
............ ..8 Leaves pubescent on the veins beneath; flowers usually pink (rarely white); shrub to 15 dm tall |
........5 Inflorescence a panicle, longer than broad; [section Spiraea]. |
............ ....9 Lower leaf surface densely tomentose with white, tawny, or rusty tomentum which obscures the surface. |
............ ......10 Follicles glabrous; [alien, rare] |
............ ......10 Follicles pubescent; [native, common in boggy wetlands] |
............ ....9 Lower leaf surface glabrous or with a few scattered hairs that do not obscure the surface. |
............ ........11 Leaves lanceolate to oblong-lanceolate, widest at or below the middle; flowers pink; [alien, rarely escaped or persisting] |
............ ........11 Leaves oblanceolate to obovate or oblong, widest above or at the middle; flowers white (rarely slightly pink); [native, of bogs, stream-banks, swampy areas, or moist to dry rocky areas]. |
............ ..........12 Leaves 3-5 (-8)× as long as wide, finely and sharply toothed; inflorescence axes, hypanthium, and sepals pubescent; sepals usually obtuse; twigs yellow-brown to brown; stamens white |
............ ..........12 Leaves 2-3× as long as wide, coarsely and bluntly toothed; inflorescence axes, hypanthium, and sepals usually glabrous or nearly so; sepals usually acute; twigs red-brown to purple-brown; stamens pink-purple |