Sexes in Ornamental Plants
Many ornamental plants are chosen for use because of their colorful
fruits. Red holly berries, orange pyracantha berries, and white snowberries
are just of few examples of the color that ornamental fruits bring to the
garden. These plants are also attractive to 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 plants have perfect flowers. Roses and viburnums are examples
of perfect flowered plants. This means that each individual flower has
both male and female parts; stamens, which produce pollen, and a pistil,
which contains the ovary(ies) which will produce the seed and hence the
fruit. This makes self-fertilization possible.
Monoecious plants are also capable of self-fertilization. Unlike
perfect flowered plants, monoecious plants have two types of flowers --
male (staminate) and female (pistillate). Both flower types occur on the
same plant. Birches and pines are examples of monoecious plants. In either
perfect flowered plants or monoecious plants, pollen is easily carried
to the stigma of the same flower or of the female flower of the same plant
by insects, birds, or wind.
In dioecious plants, pollination is not so easy. Each plant has only
male or only female flowers, so if a particular plant is the only one of
its species in an area, pollination is impossible and no fruit will result.
Hollies and yews are examples of dioecious plants. In order to ensure a
good fruit set on these plants, male and female trees must be grown within
a reasonable distance of each other. Although they need not be grown side
by side, the closer the male and female plants stand, the better the fruiting
which may be expected. One male plant can serve as a pollinator for several
female plants. It is also possible in some cases to graft a male branch
onto a female plant to enable pollination to occur.
Identification of sexes in dioecious plants is not difficult, though
sometimes it may require more than the naked eye to see the tiny flower
parts involved. Male flowers lack stigmas or have undeveloped stigmas,
and will have stamens. Female flowers have stigmas but not developed stamens.
Obviously, a plant with fruit will be a female, but a fruitless plant is
not necessarily a male. The plant may be fruitless due to lack of pollen
or because environmental conditions were not suitable for pollination.
Check the flower structure to be sure of the sex.
Occasionally the sex of dioecious plants is important because a lack
of fruit is desired. Fleshy fruit-like ginkgo seeds have an objectionable odor and
mulberry fruits can litter the ground. In such cases it may be very useful
to plant only male trees, as a female tree could receive pollen from neighboring
sources resulting in the undesirable fruit.