Arizona walnut

Trees , 5-18 m. Bark light to medium gray or brownish, divided into narrow checkered plates. Twigs with distal edge of leaf scar notched, glabrous or bordered by poorly defined velvety zone; pith brown. Terminal buds narrowly ovoid or conic, flattened, 4-7 mm. Leaves 18-38 cm; petiole 3-6 cm. Leaflets 9-15, lanceolate to lance-ovate, symmetric or falcate, 6.5-10.5 × 1.5-3.4 cm, margins serrate, apex narrowly acuminate; surfaces abaxially with capitate-glandular hairs, simple or 2-4-rayed fasciculate hairs, and often scales scattered over veins and blade, axils of proximal veins with prominent tufts of fasciculate hairs, adaxially with capitate-glandular hairs, sometimes also scattered fasciculate hairs, becoming glabrate except along major veins; terminal leaflet usually small or none. Staminate catkins 5-8 cm; stamens 20-40 per flower; pollen sacs 1.2-1.4 mm. Fruits 1-3, subglobose or short-ovoid, 2-3.5 cm, smooth, densely covered with capitate-glandular hairs and peltate scales, when very immature also fasciculate hairs; nuts globose to ovoid, 1.8-2.7 cm, deeply longitudinally grooved, surfaces between grooves smooth.

Flowering spring (Apr-May). Along streams and rocky canyon sides; 300-2100 m; Ariz., N.Mex., Okla., Tex.; Mexico (Chihuahua, Durango, Sinaloa, and Sonora).

Specimens intermediate between Juglans major and both J . microcarpa and J . nigra are discussed under the latter species.