Trees of New York State 251 



ROSACEAE 



Primus instititia L. [Prunus spinosa, var. instititia Gray] 



Black Thorn, Bullace Plum, Sloe 



Habit — Generally a bushy shrub 2-15 feet high with short, stiff, spiny 

 branches forming a dense, compact top, occasionally a small tree 20-25 

 feet in height witli a trunk diameter of 5-8 inches and a narrow, compact, 

 rounded crowTi. 



Leaves — Alternate, oblanceolate to obovate, 1^-2 inches long, broadly acute 

 at the apex, attenuate at the base, sharply and somewhat doubly serrate, 

 at maturity firm, dark green and glabrous above, paler and pubescent 

 below, borne on slender petioles, %-% of an inch long. 



Flowers — Appearing in April or May with the leaves, perfect, about ^A of 

 an inch broad, borne solitary or in 2-3-flowered, umbellate clusters from 

 . lateral buds on the growth of the preceding season. Calyx-tube campanu- 

 Ifite, green, glabrous, 5-lobed, the lobes narrow and acute. Petals 5, 

 elliptical, blunt at the apex, inserted with the stamens on the calyx-tube. 

 Stamens about 30, A\dth filiform filaments and oval anthers. Pistil green, 

 glabrous, consisting of a 1-celled ovary, a long filamentous style, and 

 capitate stigma. 



Fruit — A globular, glaucous, deep blue or nearly black drupe, %—V2 of 

 an inch in diameter maturing in July but usually persisting until winter, 

 scarcely edible. Plesh thin, acidulous. Stone oval, somewhat compressed, 

 grooved on one side. 



Winter characters — Twigs slender, glabrous, lustrous, dark browni, at length 

 becoming dark gray. Lateral spinescent spurs well devolped. Terminal 

 bud absent. Lateral buds ovate, acute, light brown, %-% of an inch 

 long. Mature bark thin, quite smooth, nearly black. 



Habitat — An "escape" that has become established along highroads, fence 

 rows and in waste places. 



Range — • Central and southern Europe, northern Africa and western Asia. 

 Naturalized in New England, Long Island, Pennsylvania, New Jersey, 

 and possibly elsewhere. Zones A, B, and C. 



Uses — OccasionaUy used as a hedge plant because of its dense habit and 

 spiny branches, but objectionable as it produces root-suckers in abundance. 

 A double-flowered form is propagated in this country for ornamental 

 purposes. Wood hard, heavy, close-grained, reddish brown with paler 

 sapwood. Used abroad in the manufacture of furniture and for cabinet 

 work. 



