Quercus turbinella aka Sonoran Scrub Oak

Quercus turbinella, or scrub live oak, belongs to the beech family, Fagaceae. It grows in the southwestern and central United States. Its range also reaches parts of northern Mexico. These include northern Baja California, Sonora, and northern Chihuahua. Oregon State places it in desert mountains among pinyon and juniper. Its range stretches from southern California east to Colorado and western Texas. This oak keeps its leaves through the year. It grows as a shrub or, less often, a small tree.

The shrub forms dense clumps and can grow into thickets. Oregon State gives a shrub height of 6–16 feet [2–5 metres]. Virginia Tech gives an upper shrub height of 15 feet [4.6 metres]. The less common tree form may reach 25 feet [7.5 metres]. Its bark is pale gray, with small, fine scales. Young twigs are thin and reddish brown. Fine tan hairs cover some of their surface. Rounded buds sit in groups along the shoots.

The leaves grow alternately rather than in pairs along each stem. Each leaf is simple, with a tough, leathery feel. Their shape ranges from oblong to oval. Virginia Tech records lengths of 0.5–1.5 inches [1.3–3.8 centimetres]. Oregon State gives a narrower range of 1.5–3 centimetres. Coarse teeth or lobes end in sharp spines. These edges give the leaves a holly-like look. The upper surface ranges from dull gray-green to yellow-green. Some leaves have a pale coating on top. The underside may be smooth or have fine hairs. Oregon State describes yellowish to reddish hairs beneath the leaves.

Male and female flowers grow on the same plant. The male flowers form hanging, yellow-green catkins about one inch long. Tiny female flower spikes sit where leaves meet the stems. The flowers emerge with the leaves. Slender acorns range from cylindrical to egg-shaped or narrowly oblong. They measure about half an inch to one inch long. A shallow, warty cup covers one-quarter to one-third of each nut. The acorns mature within one growing season. They ripen in late summer or early fall.

Oregon State lists sun as the growing exposure. The species tolerates many kinds of soil. Sandy loam through clay loam gives the best growth.