Ginkgo biloba

Trees to 30 m. Crown somewhat ovoid to obovoid, tending to be asymmetric, primary branches ascending at ca. 45° from trunk. Long shoots faintly striate; spurs thick, knoblike or to 3 cm, gray, covered with bud-scale scars. Buds brown, globose, scales imbricate, margins scarious. Leaves fan-shaped, glabrous except for tuft of hairs in axils, blades 2--9.5 × 2--12 cm, mostly 1.5 times wider than long, apices cleft to truncate; venation dichotomous, appearing parallel; leaf scars semicircular; petioles channeled on adaxial surface, 2.5--8.5 cm. Seeds obovoid to ellipsoid, yellow to orange, 2.3--2.7 × 1.9--2.3 cm, mostly 1.1--1.2 times longer than broad, glaucous, rugose, with apical scar, maturing in single season, usually 1 per peduncle, occasionally polyembryonic, outer coat foul-smelling; peduncles orange, glaucous, ridged, 3--9.5 cm, collar broadly elliptic, 7.2--8.6 mm broad. 2 n = 24.

Ginkgo is widely planted as an ornamental. The unusual shape of the crown, natural resistance to disease, and yellow leaf color in fall make this a favorite street and park tree. Ovulate trees produce an abundance of seeds, which have a particularly obnoxious odor; the planting of ovulate ginkgoes is often discouraged for this reason. Seeds (canned with fleshy outer coat removed) are sold in ethnic markets as 'silver almonds' or 'white nuts,' the gametophyte and embryo being edible. Oils from the outer coat are known to cause dermatitis in some humans.

In China Ginkgo biloba is either extinct in the wild or drastically restricted in range. The species is reported to occur naturally in remote mountain valleys in China's Zhejiang province (C. N. Page 1990). Persistence of trees planted about dwellings, however, when no trace of the dwellings remains, complicates discerning the status of such trees. Most, if not all, ginkgoes exist only in cultivation.

In the flora area seeds of ginkgo, minus the fleshy outer coat, have been found beneath various species of trees up to 150 m from the nearest seed-producing ginkgo. The dispersal agents were almost certainly birds, possibly crows. A cache of ginkgo seeds, in association with scats of raccoons [ Procyon lotor (Linnaeus), family Procyonidae], was found in a tree crotch about 50 m from the nearest source of the seeds (J. W. Thieret, pers. comm.). Apparent animal dispersal of ginkgo requires further study.

Seedlings or saplings of ginkgo are very rarely found in the vicinity of planted trees and in fencerows and woods (undocumented reports from Kentucky, New Jersey, New York, Ohio, Pennsylvania, and Virginia), hence the inclusion of the species in the flora. Nevertheless, the species is doubtfully naturalized in North America despite about two centuries of cultivation here.