Blue Palo Verde
Parkinsonia florida
(Cercidium floridum)
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Palo Verde Root Borer
Derobrachus geminatus
Long-jawed Longhorn Beetle
Dendrobias mandibularis
Digger Bee
Centris pallida
Watercolor from specimens found near
Buckeye Hills, Maricopa Co., AZ, 25 Nov. 1991. (a) Palo Verde Root
Borer, (b) Digger Bee, (c) Long-jawed Longhorn Beetle, (d) bean pod with
bruchid beetle exit hole.
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Among the caterpillars found munching the leaves may be Melipotis acontioides. The larvae hide during the day and only emerge at night to feed.
TREE: All but the lower trunk and largest branches are smooth and green,
thus even when leafless the tree can carry on photosynthesis. The trees are
very often 4 to 6 m tall, but specimens taller than 10 m are not uncommon.
FLOWERS: Profuse clusters of bright yellow, five petaled flowers in
March or April depending on elevation and rainfall. If moisture is present a
few flowers open through the summer months as well. The flowers like other
members of the Ceasalpinoidae are slightly irregular, with only a vague
similarity to typical pea flowers.
LEAVES: Two or three pairs of four leaflets form a single, compound
leaf. Drought and frost deciduous.
ARMED: Short, slightly curved spines are arranged regularly along the
twigs.
FRUIT: Seeds are very hard and smooth, slightly flattened with usu. two
seeds per tan pod. The pods (d) remain attached to the tree well into the
winter months.
RANGE: Found throughout the range of the saguaro in Arizona, but more
likely to be encountered along the larger desert washes.
Since Blue Palo Verde typically grows along washes there is likely to be deep sandy soil nearby for the Digger Bee (b). The bees provision long tubular nests in the sand with pollen and nectar gathered from palo verdes. The bees are noticeablly larger than Honey Bees. They are steel gray with large greenish eyes. John Alcock, in Sonoran Desert Summer, explores the fascinating biology of this species.
Flushing its new folliage in late May, the tender shoots of Blue Palo Verde are attractive to adult leaf beetles of the genera Cryptocephalus and Saxinus . These small, colorful beetles feed as adults on Palo Verde, but most likely have alternate host plants for larval development. The adult beetles are found mating on the new palo verde growth. Several kinds of longhorn beetles (a,c) use this tree as larvae.
A small moth develops within the developing green pods causing significant seed loss on some trees. As with injuries to mesquite, the wounds caused by insect feeding ooze sap that attracts tiny wasps, flies, and ants. This minute but vital source of sweetened moisture comes at the end of May, when the desert is usually under an extended dry spell.