Juglans major aka Arizona Walnut

Juglans major, or Arizona walnut, is a deciduous tree. It belongs to the walnut family, Juglandaceae. Its native range spans Arizona, southern Oklahoma, and northern Mexico. It grows in rocky ravines and along stream beds. These sites lie at 2,300–7,550 feet [700–2,300 metres]. The tree can live for about 400 years.

It reaches about 49–50 feet [15 metres] tall. Its trunk often forks beneath a broad, spreading crown. Young trees grow fast and form a deep taproot. The gray-brown bark has furrows and flat-topped ridges. Stout, hairy twigs turn from green to brown. Their pith has chambers, and leaf scars have three lobes. The alternate, pinnate leaves have nine to fifteen leaflets. Each leaflet has toothed edges and a narrow, curved shape. Leaves look yellow-green above and paler beneath.

Male and female flowers grow on the same tree. Wind carries the pollen, and the tree is self-fertile. Flowering runs from May to June. Male flowers hang in yellow-green catkins on older twigs. Small female flowers grow near the tips of new shoots. They occur alone or in groups of two or three. Round nuts develop inside thin husks that stay closed. The husks change from bright green to brown. Grooved nuts ripen in autumn; PFAF gives October to December. Wild trees bear good seed crops every two or three years.

Give this tree full sun and shelter from strong winds. It needs moist soil that drains well. Deep loam suits it best, though it accepts sand and clay. It tolerates mildly acid through mildly alkaline soil. PFAF lists USDA hardiness zones 8–11. Its broad crown suits the canopy of a woodland garden. Rain can wash growth-inhibiting chemicals from leaves into the ground. These may limit plant growth beneath the tree. Wildlife eats many seeds, leaving few to form new trees. PFAF reports germination rates below half.

The seeds can be eaten raw or cooked. Reports differ on their size and value as food. Some describe small seeds; others describe large, sweet kernels. Their thick shells make the kernels harder to reach. The seeds also yield edible oil, which spoils quickly. PFAF lists no known hazards or medicinal uses. That does not establish safety for every person or pet. Seed husks and young twigs provide brown dyes. Growers also use this species as rootstock.