Common Name(s): Palo Joso, Palo Hooso, Sinaloan Silk Tree, Sinaloan Albizia

Synonym(s):

Family: Fabaceae

Native To: Sonora and Sinaloa, Mexico

Native Habitat: Tropical deciduous forest and arroyos toward the coasts

Growth Habit: Large tree, growing up to about 65 feet tall

Flowering: May

Distinguishing Characteristics: Leaves are bi-pinnate, growing to roughly 10 inches in length, each are divided into 4-8 pairs of pinnae, and each of these divided again into 10-21 pairs of leaflets. Flowers are cream colored puffballs. Pods can be as long as 16 cm (6 inches) and persist through winter. Bark is smooth and pale yellow.

Natural History and Cultivation Notes: The Albizia sinaloensis on campus was collected in southern Sonora by Warren Jones in the mid 1970s. Seeds were germinated at the Campus Ag Center on Campbell Avenue in Tucson. Seed germination requires scarification and soaking in a damp towel overnight. Chuck Raetzman’s landscape crew helped to install the tree at its present site.

As far as hardiness, there are two bits of evidence. The Desert Legume Program (DELEP) in Tucson reports that the smaller test trees planted at the very chilly Campus Ag Center die back to the ground when winter temperatures drop to the low 20s F. However, Tucson’s record cold temperatures (official 19 F) of late 2003 created minimal damage to the Albizia sinaloensis on campus. Presumably the tree is large enough and the campus retains more heat than the open DELEP fields.

At more than 60 ft tall, this individual is undoubtedly the biggest of its species in Tucson, and may be the largest in Arizona. Its umbrella-shaped crown towers over a three story historical building. Because of its stature and rarity, this tree was awarded the status of “Great Tree of Arizona” by the Arizona Community Tree Council in 2004.

Ethnobotany: The bark has been used as a source of tanning leather.

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