This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
A low shrub, reaching a maximum height of about 4o, not thorny, the twigs of the season mostly puberulent. Leaves orbicular, oval-orbicular, or slightly obovate, 9"-18" long, rounded, retuse or apiculate at the apex, obtuse or truncate at the base, pubescent, at least on the nerves beneath; flowers white, about 6" broad, solitary or 2-3 together in lateral umbels, expanding with the leaves; petals suborbicular; drupe globose, 5"-8" in diameter, nearly black, with a light blue bloom; stone nearly as thick as wide, pointed only at the base.
A branching shrub, 1°-4° high, the foliage and young twigs densely soft-pubescent. Leaves short-petioled, ovate-lanceolate or oval, acute or acutish at both ends, sharply serrate, glabrate on the upper surface at maturity; flowers white, 3"-4" broad, in sessile, lateral umbels, appearing before the leaves; pedicels slender, pubescent; drupe oval-globose, 4"-5" in diameter; stone little flattened, nearly orbicular.
In sandy or dry soil, Tennessee to Kansas and Texas.
Prunus insititia L. Sp. Pl. 475. 1753.
A much-branched shrub with thorny branches, 5°-15° high. Leaves mostly obovate, obtuse at the apex, narrowed or rounded at the base, serrate, nearly glabrous above when mature, pubescent beneath; flowers white, about 4"-6" broad, appearing before the leaves, the lateral clusters usually only 1-2-flowered; pedicels 1/2'-1' long; drupe globose, nearly black with a bloom 6"-10" in diameter; stone little flattened, acute on one edge, ridged and grooved on the other.
Along roadsides and waste grounds, New York to Massachusetts. Naturalized or adventive from Europe. April-May. Has been mistaken for P. spinosa L.
Prunus doméstica L., the Garden Plum, a small tree, with larger fruit, flowers and leaves, has locally escaped from cultivation.
Prunus pumila L. Mant. Pl. 1: 75. 1767.
Prostrate and spreading or ascending, much branched from the base, sometimes bushy, 6'-6° high. Leaves mostly oblanceolate or spatulate, acute or acutish at the apex, narrowed at the base, serrate, especially toward the apex, usually pale beneath and deep green above, glabrous or very nearly so on both sides when mature; flowers white, 4"-s" broad, appearing with the leaves in sessile lateral umbels; clusters few-flowered; drupe 4"-6" in diameter, dark red or nearly black when mature without bloom; flesh thin, acid.
On sandy or gravelly shores, New Brunswick to Manitoba, Maine, New Jersey, Indiana and Wisconsin, April-May. Fruit ripe in August. Beach-plum.