Autotetraploid Induced Sterility in the Pink and White Shower Tree

The copious production of messy and sometimes hazardous fruits and seeds make the normal diploid forms of many tropical landscape species high maintenance and potentially invasive. A sterile form of the prolific seed producing pink and white shower tree, Cassia javanica (L.), would be highly desirable for tropical landscapes. Triploid plants are usually sterile, and can be produced by crossing tetraploid and diploid plants of the same species. In a first step toward creating triploid C. javanica plants, several tetraploid and mixoploid individuals resulted from colchicine treatments on seedlings. Upon flowering, all four 5-year-old autotetraploid C. javanica plants were completely sterile, and remained sterile in their second year of flowering.  Among 11 mixoploid plants that flowered, 10 were as prolific seed producers as the diploid control plants, and one individual was completely sterile both years of flowering. It is not uncommon for autotetraploid plants to have reduced fertility, but complete sterility, although welcomed, was unexpected. The sterile autotetraploid plants will be airlayered for introduction to the Hawaii landscape industry.