Parkinsonia florida (Benth. ex Gray) S. Wats.

by Kirsten Larsen, Native Plants of Arizona 2004
Common names: Blue paloverde (9), blue palo verde (1,3).
Family: Fabaceae (1)
Synonymy: Cercidium floridum Benth. ex Gray (9,6), Cercidium torreyanum (S. Wats.) Sarg. (2,5), Parkinsonia torreyanum S. Wats., Cercidium torreyanum Sarg. Gard. & For. (6)
Etymology: Parkinsonia honors the English botanist John Parkinson. The former genus name Cercidium used in many of the published references below signifies the resemblance of the legume to a Greek weaver’s comb, a kerkidion. The species name florida (or former floridum) refers to the profuse flowering habit (8).

Identification
Growth form: Tree up to 10 m. tall, generally <8 m. tall (7), trunk up to 0.5 m. in diameter, widely spreading open crown spreading up to 15.2 sq. m. (2,4).
Roots: Do not have mycorrhizal nodules (2)
Stem: Multiple stems, thin bark, glaucous, blue-green becoming brown and scaly on large older trunks (4), photosynthetic, straight nodal spine 6.4 mm. long (2,3,4), branches +/- zig-zagged (7).
Leaves: Drought-deciduous, dull bluish green, sparse, alternate, bipinnately (even-2-pinnate) compound, 2.5 cm. long (2), 1 pair of pinnae, each with 1-3 pairs of oblong leaflets, leaflets 4-8 mm. long (3,4), petioled (7).
Inflorescence/flowers: Inflor. a raceme, axillary, <7 flowers (7), commonly 4-5 flowers in a cluster (4). Flowers bright yellow, slightly bilateral, on slender pedicels 12-17 mm. long, upper petal (banner) with a few red-orange spots or not (6,7). Calyx 6-7 mm. long, sepals +/- free and all alike. Petals 5 (4), 8-10 mm. long (3), banner circular, 6-8 mm. in diameter, the claw 3-4 mm. long, the rest of the petals ovate attenuate (6). Stamens 10, exerted, free (7).
Fruit: Flat smooth yellowish brown legumes 4-12 cm. long, slightly narrowed between seeds or not (7), short pointed at end (4), tip beak like (7), with 1-8 (usually 2-3) oblong-ovoid seeds (2,3). Seeds 8-10 mm. long, 6-7 mm. wide, smooth, olive to brown (3), tardily dehiscent, the 2 valves papery, commonly maturing in July (8).
Similar species: Parkinsonia microphylla has smaller leaves, one whitish petal, yellowish bark, spine tipped branchlets, and flowers later (4,6). In Trans-Pecos Texas there seems to be an overlap between Parkinsonia texana making it difficult to distinguish the two (8).

Ecology
Life history: Small tree or subtree (2), perennial (9).
Native/introduced: Native to the Southwestern United States (9).
Photosynthetic pathway:
Phenology: Flowers March to May (3), occasionally August to October (5).
Distribution: Throughout the Sonoran Desert in desert scrub and desert grasslands; from central and southwestern Arizona into southeastern California and southward through western Sonora, Mexico (2) and Trans-Pecos Texas (8). Disjunct populations are located in northern Sinaloa and Baja California Sur. It has been classified as a facultative desert riparian species that may be limited to washes and arroyos and can be a dominant species in parts of its range (2,4,6). Elevation 500-4,000 ft. (4).

Uses
The Cahuilla Indians dried the fruits (beans) to grind into flour for mush or cakes and used the trees for shelter. The Yuma Indians roasted and ground the seeds for mush, or parched the seeds till almost burnt as a famine food. The Pima Indians ate the green pods raw and used large branches or trunks to make ladles and cooking tools (10,2). Ungulates can browse the twigs and leaves and small mammals consume the seeds. Also used by breeding birds. A nurse plant for saguaro (2). Ornamental species (7). Arizona state tree (4).

References

1. Retrieved [November, 12, 2004], from the Integrated Taxonomic Information System on-line database, http://www.itis.usda.gov.

2. Pavek, Diane S. 1994. Cercidium floridum. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [ 2004, November 11].

3. McDougal, W.B. 1973. Seed Plants of Northern Arizona. The Museum of Northern Arizona. Flagstaff, Arizona.

4. Epple, A. O. 1995. A Field Guide to the Plants of Arizona. Falcon Publishing. Helena, Montana.

5. Kearney, T. H., R. H. Peebles, and collaborators. 1960. Arizona Flora 2nd Edition. University of California Press, Berkeley and Los Angeles, California.

6. Benson, L. and R. A. Darrow. 1981. Trees and Shrubs of the Southwestern Deserts (3rd ed). University of Arizona Press, Tucson.

7. Hickman, J. C. (ed).1993. The Jepson Manual; Higher Plants of California. University of California Press, Berkley and Los Angeles, California.

8. Vines, R. A. 1960. Trees, Shrubs, and Woody Vines of the Southwest. University of Texas Press, Austin, Texas.

9. USDA, NRCS. 2004. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

10. Moerman, D. 2003. Native American Ethnobotany Database (http://herb.umd.umich.edu/). University of Michigan, Dearborn, MI 48198 USA.