Prunus L.
Family: Rosaceae
Cherry, Plum
Prunus image
Aaron Carlson  

Key to Wisconsin Prunus

    • 1a.Inflorescences racemes, 12–20-flowered. 2

    • 1b.Inflorescences corymbs or umbels, with 12 or fewer flowers. 3

    • 2a.Leaves ovate or elliptic to lanceolate, broadest at or below the middle, glossy above, the margins with incurved or appressed teeth; sepals with margins usually entire, rarely with a few glandular teeth; hypanthia persistent. P. serotina

    • 2b.Leaves elliptic to obovate, broadest at or above the middle, dull above, the margins with ascending to spreading teeth; sepals toothed, erose; hypanthia deciduous. P. virginiana

    • 3a.Flowers and fruits sessile; ovary and fruit pubescent. 4

    • 3b.Flowers and fruits pedicellate; ovary and fruit glabrous. 5

    • 4a.Youngest twigs pubescent; leaves densely pubescent below; fresh fruit less than 1.5 mm in diameter, red. P. tomentosa

    • 4b.Youngest twigs glabrous; leaves glabrous below, sometimes with a few hairs on the midveins; fresh fruit more than 1.5 mm in diameter, yellow to orange. P. persica

    • 5a..Calyx lobes glabrous (or with glandular margins); fruit (cherries) not grooved, not glaucous, the pit round. 6

    • 5b.Calyx lobes pubescent, at least at the base; fruit (plums) with a shallow groove, the pit somewhat flattened. 8

    • 6a.Low, spreading shrubs with decumbent or ascending branches; leaves oblanceolate to obovate-elliptic, marginal teeth obscure or absent proximally; calyx lobes glandular. P. pumila

    • 6b.Erect small trees or bushy shrubs; leaves ovate to obovate, toothed along the entire margin; calyx lobes eglandular. 7

    • 7a.Inflorescence a corymbose-raceme with a central axis; petals glabrous; leaves broadly ovate, oblanceolate, or suborbiculate; fruit black. P.mahaleb

    • 7b.Inflorescence umbellate (to corymbose); petals hairy on the outside near the base; leaves elliptic, oblong-lanceolate or lanceolate; fruit red. P. pensylvanica

    • 8a.Leaf teeth sharp, glandless; calyx lobes eglandular. P. americana

    • 8b.Leaf teeth gland-tipped or rounded; calyx lobes glandular. P. nigra

This is the genus of popular “stone fruits” including cherries, plums, peaches, apricots, and nectarines, as well as almonds. Prunus serotina is our only large tree in the genus, the others are shrubs or can form small trees if conditions are right. The flowers of cherries and plums are easily recognized with their perigynous hypanthium and monocarpic pistil. Many species flower before formation of the leaves.