[4] The Mexican blue oak is a small evergreen tree growing 5–8 metres (16–27 feet) tall with a rounded crown.

The leaves are small, alternate and oblong, with entire margins, leathery, bluish-green above and mid green below.

The light brown acorns are ovoid or oblong, about 2 cm (3⁄4 in) long and lodged in scaly, bowl-shaped cups about one third the length of the nut.

[8] where it grows in association with species of pine and juniper, Arizona rosewood (Vauquelinia californica), shrubby buckwheat (Eriogonum wrightii), catclaw mimosa (Mimosa aculeaticarpa), bullgrass (Muhlenbergia emersleyi), plains lovegrass (Eragrostis intermedia), fendlerbush (Fendlera rupicola) and wolftail (Lycurus phleoides).

The fast growth and beautiful blue foliage makes selections from trees in Arizona the best for cultivation.