The December 10, 2005 Botany Photo of the Day entry shows a bleached fruit of the rare Rehderodendron macrocarpum. The same tree is pictured in today’s entry, this time as it’s beginning to open its flowers.
Eric’s photograph was taken just after a rain shower, which explains the iridescent quality of the blooms. When fully open, the petals splay out to expose prominent anthers (these can be seen poking out of the rounded, barely open buds–more photos). The individual flowers are a huskier version of those of Styrax japonicus (Japanese snowbell), and like the snowbell, borne in ample clusters all along the undersides of the spreading branches. A tree in full flower is a wonderful sight and not soon forgotten. The Garden now has at least one other species in the collection, tentatively identified as Rehderodendron indochinense H. L. Li, and both species fill the air with their rich, lemony aroma when flowering.
Other than the lack of available seed, there seems little reason for the virtual exclusion of Rehderodendron from commercial horticulture. Unfortunately we have only the one tree of this species, and without cross pollination (i.e., a source of different pollen), viable seed is seldom produced. Like other plants in Styracaceae, siting in humus-rich, well-drained soil is essential for good growth and longevity. We know this species to be hardy to Zone 8.