Dichogamy in Acer saccharum

A study of dichogamy in Acer saccharum Marsh. (sugar maple) has shown that both protandry and protogyny occur in this species. The two conditions were represented equally in the population investigated. Synchronization of blooming periods of flowers of opposite sexes resulted in reciprocal pollination between trees with different dichogamous conditions. On protogynous trees a slight overlap in blooming occurred between male and female flowers when air temperatures were near average. The period of overlap became longer when temperatures dropped below average. Conversely, higher than normal temperatures resulted in an increased tendency toward complete dichogamy, primarily because of early desiccation of the stigmas. Abnormally high or low temperatures seemed to exert little effect on the duration of the blooming periods of flowers of either sex on protandrous trees.