2017 ASHS Annual Conference

The pink shower tree, also known as the dwarf apple blossom tree, Cassia bakeriana (Craib), in the Fabaceae (subfamily Caesalpinioideae) and native to the forested areas of Thailand and Myanmar, grows to 7 to 10 meters high and wide. It is spectacular when in bloom with showy and mildly fragrant pink-purple flowers on 10- to 25-cm-long drooping racemes with 20 to 40 flowers per raceme in March and into May. However, the liberal production of 40- to 50-cm-long malodorous fruits make the normal diploid form of this species high maintenance and undesirable for areas with foot traffic, and potentially invasive. A sterile form of this prolific seed producing tree would be highly desirable for tropical landscapes. Triploid plants are usually sterile and can usually be produced by crossing tetraploid and diploid plants of the same species. In a first step toward creating triploid C. bakeriana plants, tetraploid and mixoploid individuals were induced from colchicine treatments on recently germinated seedlings. Upon flowering, two 5-year old autotetraploid and three mixoploid C. bakeriana plants were completely sterile, and remained sterile in subsequent years of flowering. It is not uncommon for autotetraploid plants to have reduced fertility, but complete sterility was unexpected, however welcomed. The sterile autotetraploid plants are being vegetatively propagated for introduction to the Hawaii landscape industry.