Quercus wislizeni aka Sierra Live Oak

Quercus wislizeni is an evergreen oak in the beech family, Fagaceae. Its common names include interior live oak and chaparral oak. Its native range runs from California into northern Baja California, Mexico. In California, it reaches north to Siskiyou County. It grows in canyons, on slopes, and across valleys. Its habitats also include chaparral and pine and oak woods. Oregon State does not list it as native to Oregon.

This tree grows 30–75 feet (9–23 metres) tall. It stands upright and usually has one main stem. The trunk is short, with branches that rise or spread. These branches form a broad, rounded crown. In some trees, the leaves reach down to the ground. Young bark is smooth and gray to greenish brown. Older bark turns very dark and develops uneven furrows. Scaly ridges break up the surface of older stems. Young twigs have fine hairs and a greenish brown hue. Their orange-brown buds cluster together and have broad, pointed shapes.

The leaves grow in an alternate pattern along the twigs. Each leaf is simple, leathery, and retained year-round. Sources give leaf lengths of about 1–2 inches. Their shapes range from oblong to oval or lance-shaped. Most leaves lie flat and end in a sharp tip. Their edges may be smooth or bear sharp, spine-like teeth. The upper face shines dark green. The lower face is lighter green or yellow-green and also shines.

Male and female flowers grow on the same tree. Both appear in early spring as new leaves emerge. The male flowers hang in slender, yellow-green catkins. Sources give catkin lengths of roughly 0.8–3 inches. Tiny female flowers form groups of two to four. They sit where upper leaves join the stem. The acorns take two growing seasons to mature. Each nut is narrow and tapers toward its pointed end. A scaly cup holds about one-third to one-half of it. Some nuts show lengthwise stripes on their surface.

Oregon State lists sun as the growing exposure. It also gives USDA Zone 7 as the hardiness threshold. The evergreen leaves and broad crown define its landscape form. Its foliage can extend from the crown nearly to ground level.