Mariosousa willardiana

Accession Count: 26
Common Name: Palo Blanco, Willard acacia
    • Select which
      accessions to find:

























Family Name: Fabaceae
Botanical Name: Mariosousa willardiana
Synonyms:
Botanical Synonyms: Acacia willardiana
Family Synonyms: Leguminosae
Sub Species:
Variety:
Forma:
Cultivar:
Characteristics: M. willardiana is a slender tree reaching anywhere from ten to twenty feet tall. It has thornless branches, and a distinctive silver-white bark that is smooth, papery and exfoliates from the trunk. The evergreen tree has a weeping canopy consisting of flattened petioles, and four inch long, medium green leaflets. Throughout the spring, the palo blanco can be seen displaying white, cylindrical flowers (5).
Compound: Mar wil
Geographic Origin: Sonora, Mexico
Ecozone Origin: Nearctic
Biome Origin:
Natural History: The Willard acacia is native to the Sonoran Desert, specifically regions of Sonora, Mexico and northern areas of Sinaloa, Mexico to the south. M. willardiana is found in areas with rocky hill slopes and hill crests (2).
Cultivation Notes: Just like many other plants native to warm, dry regions, M. willardiana grows best in full sun and requires water twice a month, but is able to survive a month without it. It is not the most cold tolerant of trees, only able to withstand temperatures as low as 28oF. In fact, palo blanco's are best grown in frost-free areas and recommended that they are planted against a wall for warmth (5). 
Ethnobotany: The common name ‘palo blanco’ translates directly into English as ‘White Stick,’ a reference to M. willardiana’s white, papery bark. Palo blanco wood  was often used by the Seri Indians of northern Mexico for building material because of this plant’s characteristically straight and minimally branched trunk (4). 
M. willardiana is great for transition and mini-oasis landscapes. The tree's thornless, weeping canopy makes for light shade that is great for succulents and patios. Willard's acacia is often used for patios by itself, and in groups when creating a grove effect (5). 

Height: 16 - 20 feet
Width: 11 - 15 feet
Growth Rate: Fast Growing
Grow Season: Fall
Flower Season: Spring
Color: White
Function: Shade
Spread: Non-spreading
Allergen: Non-allergenic
Invasive: Benign
Toxicity: Benign
Hardy: Semi-hardy
Water Use: Low water Use

Citations:
1. Acacia willardia in: University of Arizona Cooperative Extension
4. Phillips, S.J. and Comus, P.W. (2000). A Natural History of the Sonoran Desert. Tucson: Arizona-Sonora Desert Museum Press. Print.
5. Walters, James E, and Balbir Backhaus. Shade and Color with Water-Conserving Plants. Timber Press, 1992.
Alert

Mariosousa willardiana