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..
Amygdalus persica L. Sp. Pl. 472. 1753.
A small tree, the purplish-brown twigs glabrous. Leaves mostly lanceolate or oblong-lanceolate, 3'-5' long, 8"-18" wide, glabrous on both sides, long-acuminate at the apex, usually narrowed at the base, finely serrulate nearly all around, thick-ish; petioles 1"~3" long; flowers pink, 1/2'-2' broad, scaly-bracted; drupe subglobose, grooved, softly velvety, 1 1/2' - 3' in diameter.
Escaped from cultivation, New York to North Carolina and Florida. April-May.