Culture
Winter hardy to USDA Zone 9b where it is grown in average, medium moisture well drained soils in full sun. Established trees have some drought tolerance. Site in locations protected from drying winds. Intolerant of hard frost.
'Wilhelmna Teeney' is a sterile hybrid that should be propagated by grafting or air layering.
Noteworthy Characteristics
Cassia × nealiae, commonly called rainbow shower tree, is a hybrid cross between C. fistula (golden shower tree) and C. javanica (pink-and-white shower tree). It typically grows to 30-50' tall. It is noted for producing a show-stopping bloom of lightly-scented, 5-petaled flowers in 8-12" pendant racemes from April to September, with the biggest concentrations of bloom occurring in July-August. Flower colors include various shades of white, yellow, pink, orange and red, with a flower typically containing two or more combinations of these colors. Each even-pinnate compound leaf (to 12-16" long) has 5-12 pairs of elliptic leaflets (each leaflet to 4" long). Some leaf drop usually occurs in March/April as a prelude to flowering, with leaves returning as flowering begins. This tree is often considered to be semi-deciduous or semi-evergreen because of the brief loss of leaves prior to flowering. Rainbow shower tree was first observed in Hawaii as a natural hybrid. Upon discovery of this hybrid, forester David Haughs (1861-1932) began purposefully pollinating the flowers of C. javanica with pollen from C. fistula to create additional plants. Distribution of the hybrids to the public began in 1918, subsequently resulting in extensive planting of the trees throughout Hawaii. Today, rainbow shower tree is one of the most common street trees now growing along major roads in Honolulu. The common name of rainbow shower tree refers to the shower of rainbow-colored spent flower petals that, at times, rains downward to carpet the ground. Advantages of this hybrid over the individual parents include (1) it is sterile, which results in better and more abundant flowering than either parent (2) it has a fuller canopy of foliage over the winter months, (3) it blooms for a longer period of time, and (4) it produces few if any seed pods which create clean-up issues when they ripen and fall.
Genus name comes from the Greek name for a genus of leguminous plants which provide the senna leaves and pods important in pharmacy.
'Wihelmina Tenney' is a yellow and pink flowered form that was first discovered growing in Hawaii around 1920. An offspring of the original plant was donated in the late 1940s to the Foster Botanical Garden by Wilhelmina Teeney for whom the cultivar is now named. In 1965, 'Wihelmina Tenney' was designated by the City Council of Honolulu as the official tree of Honolulu.
Problems
No serious insect or disease problems. Plants have some tolerance for brief light frost with temperatures to 25°F. Mildew and leaf spot may appear. Sterile hybrid that is usually propagated by grafting or air layering.
Uses
Ornamental landscape tree. Shade tree.