The rainbow shower tree is a cross between Cassia fistula and Cassia javacana. Territorial forester David Hughes made the hybrid by hand-pollinating the two species in 1918. It quickly became a botanical sensation and was extensively shared. Unfortunately, the progeny varied widely as they were not true to seed, which is a frustrating problem due to the rare occurrence of seed production.
In 1960 The Surveyor General of Territory of Hawaiʻi, Walter Wall, perfected the grafting method for the rainbow shower tree. He distributed many trees to beautify our public spaces. As a result, Honolulu adopted the pink and yellow hybrid as its official city and county tree.
Today, many cultivars exist with various colors and fragrances. Grafting is the superior propagation method. Air layered trees have shallow root systems that easily blow over in the wind. A clean tree, it doesn’t litter the ground with sticky seed pods that stain or leaf debris, although some leaf and flower litter should be expected.
Energy is spent efficiently by allocating resources on flower and leaf production rather than on the abundant seedpods as other Cassias have. That means exceedingly showy flowers that bloom much longer than other ornamental Cassias.
- Nitrogen fixer
- No dangers