Forest & Kim Starr

Family

Fabaceae

Botanical Name

CASSIA x nealiae

Plant Common Name

Rainbow-shower-tree

General Description

So floriferous and colorful when in bloom, the rainbow-shower may seem unnatural to the eye. The yellow and pink blossoms look cheerful and festive. This hybrid was created in Hawaii in the mid-20th century, and is the result of crossing golden shower (Cassia fistula) with appleblossom cassia (C. javanica). Its species name honors Hawaiian botanist Marie C. Neal. In 1965, the city of Honolulu designated the rainbow-shower its official tree.

This moderately fast-growing tree is semi-evergreen to deciduous, depending on winter temperatures and drought. It develops a somewhat open, spreading and drooping canopy. The leaves are compound, comprising six to 10 large oval leaflets. During the intense light and warmth from spring to early autumn, branches fill with hundreds of thousands of fragrant blossoms. The flower buds often are blushed rosy cerise. Hints of scarlet aren't uncommon. Open petals are shades of yellow but then become progressively more pink as they age. Rainbow-shower is a sterile tree, so no seed pods form.

For finest canopy growth and most abundant flowering, plant rainbow-shower in full sun and any moderately fertile, well-drained soil. The warmer the summer and drier the winter, the more beautiful the tree will become. Moist soil in summer sustains the leafy growth, but the drier soil in winter helps time flower production to explode in the spring months. Use rainbow-shower as a specimen shade or street tree.

Several cultivars exist of this hybrid. Yellow-orange blossoms occur on 'Lunalillo Yellow, while 'Nii Gold' produces gold buds that open to bright yellow. 'Wilhelmina Tenney' boasts petal exteriors of cerise-pink, with flower interiors of yellow. Pale yellow flowers that fade to near white occur on 'Queen's Hospital White'.