Parkinsonia florida

Parkinsonia florida
Tree in flower
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Fabales
Family:	Fabaceae
Subfamily:	Caesalpinioideae
Tribe:	Caesalpinieae
Genus:	Parkinsonia
Species:	P. florida
Binomial name
Parkinsonia florida (Benth. ex A.Gray) S.Wats.

Parkinsonia florida (Blue Palo Verde; syn. Cercidium floridum) is a species of palo verde native to the southwestern United States (southeastern California, southern Arizona) and northwestern Mexico (Sinaloa, Sonora, Baja California). Its name means "green stick" in Spanish, referring to the green trunk in which the tree does photosynthesis.

It appears somewhat more drooping than the related Parkinsonia microphylla (Foothill Palo Verde). It is found primarily in desert washes as opposed to the foothills, a result of its greater need for water, although a few can be found in the hills. It is a quick growing tree, maturing much faster than Foothill Palo Verde and it rarely reaches ages of 100 years. It is also much taller, growing to heights of 10–12 m. Its leaves are a bluish green (hence its common name) and it also has the ability to shed them in periods of low rainfall.

The flowers of Blue Palo Verde are bright yellow, pea like blossoms which cover the tree in late spring. They are accompanied by seed pods which are slightly larger and flatter and have harder shells than Foothill Palo Verde.

The Irish botanist Thomas Coulter was the first to categorize the plant. He obtained specimens near Hermosillo, Sonora, Mexico, in 1830.

The Blue Palo Verde is the state tree of Arizona.

References

• Germplasm Resources Information Network: Parkinsonia florida
• Arizona State Tree (pdf file)