T. Davis Sydnor
Colorful fruits are important assets for ornamental trees and shrubs. Many ornamental plants decorate gardens and landscapes with red, orange, yellow, blue, purple, gray, black and white fruits. These fruiting ornamentals are also a great attraction to wild birds. Unless the sex characteristics of the plant are known, however, the homeowner may be disappointed because there may be no fruit crop even though bloom occurs.
Many species of plants such as roses and viburnums have perfect flowers. Each individual perfect flower has both stamens and a pistil (both sexes). Sexes are separate in some other plants. When male (staminate) flowers and female (pistillate) flowers are borne on the same individual plant, the plant is called monoecious. Birches and pines are examples. In perfect flowered and monoecious plants, pollen is carried to the stigma of the same flower or of the female flower of the same tree by insects, birds or wind.
In dioecious plants, male flowers appear on one plant and female flowers on another. Many homeowners complain that flowers do not set fruits on some of their trees and shrubs. In many cases, the reason for non-bearing is that those plants are dioecious. To have fruits on dioecious plants, male and female plants must be grown within a reasonable distance of one another. Although both sexes need not necessarily be grown side by side, the closer the male and female plants stand to one another, the better the fruiting that may be expected. Sometimes it is a good idea to graft a male branch to a female plant to ensure pollination.
Identification of sexes in dioecious plants is not difficult. Fruiting plants are female. Fruitless plants are not necessarily male because even mature female plants fail to bear fruits without a supply of the right kind of pollen at the right time. Identification of sexes is easy at blooming time. In certain species, sex identification requires a hand lens. Male flowers lack stigmas or have undeveloped stigmas. On the other hand, female flowers have well developed ovaries and stigmas but not developed stamens. The photos illustrate typical flowers of both sexes of four common woody ornamentals.
Ripe fruits of ginkgo have an objectionable odor, and mulberry fruits litter the ground when they ripen and fall. In such cases, knowledge of plant sex is helpful. It is advisable to plant only male ginkgo and mulberry trees because female trees might bear fruit, their flowers receiving pollen from distant trees.
NOTE: Disclaimer - This publication may contain pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registrations, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author and Ohio State University Extension assume no liability resulting from the use of these recommendations.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-6181