In yards throughout Phoenix and other areas in the Southwest, the vivid blue winter sky is punctuated by a tree covered with 2-foot long flowering stalks that look like curving yellow candles. This is the winter bloom of cascalote (Caesalpinia cacalaco). Up close, the pyramidal stalk is made up of dozens of half-inch, bright sulphur-yellow flowers with dark, orange spots on the lower petals. The fruit is almost as attractive: reddish 4-inch-long seed pods hang from the branches, looking like strings of red pearls.
Cascalote is native to the deciduous thorn forests and tropical forests of southern Mexico. Mature trees are up to 30 feet tall with a wide, spreading crown. The 4-8-inch compound leaves are made up of dark green, rounded, 1-inch leaflets. When natural conditions are dry, the plant will lose its leaves until rains return, but in gardens, it is evergreen or nearly so.
Young trees have numerous small stems arising from the base. These young stems are laced with flattened, reddish brown thorns. As the plant ages, the thorns widen, become woody, and eventually fall off, revealing a smooth, dark brown bark. Like most trees in this family, young trees are shrubby and often multi-trunked, but are easily trained to a single trunk as they mature. New stems are strongly tinged with red or purple adding extra zing to the tree even when young.
Prune selected stems in the spring to train the tree and resist taking more than a quarter of the plant in one season. Work toward your final objective gradually, taking out a few stems each year. Plants bloom on new wood, so pruning in the late summer or fall severely restricts flowering.
Flowers may be damaged at 30 degrees, but the plant is hardy to 20 degrees with minimal damage. Plants have experienced cold as low as 16 degrees and recovered as multi-branched shrubs.
Cascalote grows best in full sun. Though it tolerates dry, rocky soils, it will grow more quickly in deeper soils. Water by providing deep soaks at long intervals every 3 to 4 weeks in winter, and every 2-3 weeks in summer for established trees. Plant your tree where its exquisite winter bloom can be best enjoyed, at the edge of a garden within site of a pool or patio, to fill a corner spot or to accent a larger bed.
Cascalote is susceptible to psyllids in the late spring. Without treatment, these insects can defoliate the tree. However, cascalote will recover rapidly after such an infestation, even without treatment.
Photos courtesy of the University of Arizona Campus Arboretum