One of the great delights of walking randomly in the Arnold Arboretum is the unanticipated discovery of a plant heretofore unnoticed. This week, Grewia biloba, a shrub I had never seen in flower, presented itself in full (but subtle) glory.
The small white flowers with bright yellow eyes of stamens (pollen-producing structures) are stunning. What appear to be showy white petals are actually sepals that are green on the underside. In the upper left image, you can see the green lower surface on the partially reflexed sepal of a just-opened flower. The white petals are so small that they are mostly hidden by the yellow stamens, but if you examine a flower closely, you will find them. Lower left, pollinator services being rendered. Lower right, the magnificent splotch of a stigma, fully extended beyond the stamens, coated with yellow pollen.
Although there are nearly 300 species of Grewia worldwide, the genus is almost exclusively tropical and subtropical, so not something you run across in Boston often. However, G. biloba harkens from the warm temperate regions of China, Taiwan, and Korea, and seems happy enough here. It belongs to the same family as linden trees and you can find our few specimens properly situated at the periphery of our linden collection. They are definitely worth seeking out this week.
Nomenclatural trivia: Grewia was named by Carl Linnaeus in honor of Nehemiah Grew (1641-1712). Grew was one of the great early microscopists and plant anatomists. To see a digitized copy of his seminal work, The Anatomy of Plants, head here. The images at the back of the volume are magnificent.