Viburnum opulus L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Shrub 1–5 m; young stems smooth; petioles 1–3 cm, with 1–6 large glands near the apex; stipules slender; lvs maple-like, palmately veined, 3-lobed, coarsely toothed, basally obtuse to truncate, hairy beneath, especially on the veins; cymes 5–10 cm wide, on peduncles 2–5 cm; marginal fls neutral, with enlarged, slightly irregular cor 1.5–2.5 cm wide; fr red, 10–15 mm; stone flat, suborbicular, not grooved; 2n=18. Var. americanum Aiton, the high-bush cranberry, with the petiolar glands stalked, round-topped, and mostly higher than wide, occurs in moist woods from Nf. to B.C., s. to Pa., n. O., Io., and Wash. June. (V. trilobum) The Eurasian var. opulus, the Guelder rose, with the petiolar glands mostly sessile, concave-topped, and wider than high, occasionally escapes from cult. June, July. The cult. Snowball is a form of var. opulus with all fls neutral and enlarged.