Fabaceae, Pea Family
Tree 15 feet to 20 feet tall, 10 feet to 15 feet wide
Western Sonora and northwestern Sinaloa, Mexico
Rocky bajadas, slopes and arroyos from 0 to 2,000 feet elevation; Sonoran desertscrub and thornscrub
Living Desert Location:
Chase Administration, Foothills of Sonora Garden
One of palo blanco’s many attributes is its light colored, paper-like exfoliating bark.
Palo blanco, which means “white stick” in Spanish, is a small desert tree species named for its whitish colored trunk. Utilized as an accent rather than a shade tree, it provides an attractive, soft, vertical element in a landscape without requiring lots of space. This tree is perfect for courtyards, entryways, pocket beds, and small spaces where in time a larger tree might be a problem.
The foliage consists of twice-compound leaves with two to eight small leaflet pairs well spaced oppositely to alternately along a strap-like central midrib, or petiole, that can be up to 12 inches long. The small pairs of leaflets are shed from the elongated petiole in response to dry conditions, or during the summer months. The flattened petiole then carries on with a large part of the plant’s photosynthesis. This photosynthesizing leaf petiole, or phyllode, is common in some Australian acacias, yet sets Acacia willardiana apart from other New World acacias.
It has a narrow, upright growth form that reaches 15-20 feet tall and 10-15 feet wide in maturity. It prefers warm, sunny locations and well draining soil. Palo blanco makes one-inch to three-inch long, catkin-like pale yellow flower spikes from February to July, which are followed by long, thin, somewhat persistent seed pods.