The two words are used in describing the dichogamy of a pecan variety. Pecan trees are generally cross-pollinated in nature because within a pecan variety, the maturation of the staminate (male) and pistillate (female) flowers occur at different times. This condition is known as dichogamy. A protandrous variety such as Desirable has catkins (male flower) which mature first and release their pollen, followed by the nutlet (female flower) becoming receptive to pollen after pollen shed of the Desirable trees is past. A protogynous variety such as Schley or Elliott has female flowers which mature and become receptive before the catkins mature and release their pollen. Some publications list dichogamy by type, with protandrous cultivars referred to as type I and protogynous cultivars referred to as type II. When planning an orchard, both type I and type II varieties need to be included to ensure pollination of all varieties. For example, Elliott pistillate flowers are receptive when Desirable is releasing pollen, followed by Desirable nutlets becoming receptive when Elliott is releasing pollen. A variety which has no overlap in pollen release and nutlet receptivity is said to have “complete dichogamy”.
Question answered by Dr. Charles Graham, Pecan Research-Extension Station horticulturist.