And P. baccata L., the Siberian crab, occasionally escape from cult. Both differ from P. malus in their glabrous or subglabrous hypanthium, pedicels, and lvs, and small, tart fr. P. prunifolia has pubescent twigs, persistent cal, and fr ca 2 cm. P. baccata has glabrous twigs, deciduous cal, and fr ca 1 cm.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.