Imperfect flowers are flowers that only have one set of reproductive organs, so they are considered to be either male or female. Flowering plants can fall into two categories of imperfect flowers: monoecious or dioecious. The first occurs when a plant has some flowers that contain only the pistil, or female reproductive part of the flower, while other flowers on the same plant only contain stamens, the male reproductive part of the flower; self-fertilization is possible with monoecious plants, and pollination can also occur by other sources such as the wind or insects. Dioecious plants, on the other hand, are made up of flowers that are either male or female; as a result, male and female versions of the plant must exist near each other in order for pollination to happen at the hand of outside sources.
Categories of Reproduction
All flowers fall into one of three categories of reproduction: perfect, imperfect, or incomplete. Perfect flowers, such as roses, are flowers that contain both a pistil and stamens, and therefore are both male and female. Imperfect flowers are either male or female, and a plant can contain male or female flowers, or both. The incomplete flower can be either perfect or imperfect, but is missing one of the four major parts of a flower: the pistil, stamens, petals, or sepals. If a flower is unable to reproduce on its own, pollination can occur to allow for fertilization and reproduction to take place.
Pollination
The process by which plants reproduce is known as pollination; during this process, pollen containing sperm from the male flower is transferred to the female flower, which typically results in new life. While perfect flowers can reproduce entirely within one bloom, imperfect flowers need two separate flowers, a male and a female, in order to pollinate and create seeds. When both organs are not present on flowers of the same plant, a plant of the opposite sex must live nearby for pollination to happen. Pollen can be transferred by animals, insects, weather, or humans, but an imperfect flower will usually need some sort of outside facilitation in order to reproduce.
Monoecious and Dioecious
Imperfect flowers grow on one of two types of plants, monoecious or dioecious. Monoecious plants have both male and female flowers, while dioecious plants are either male or female. As opposed to the moneocious plant, which contains both sexes in close enough proximity to self-fertilize, the dioecious version requires that a plant of the opposite sex reside close enough for pollination to take place. In this instance, there typically needs to be intervention by outside sources, such as insects, in order to pollinate the female flowers. Some horticulturists consider imperfect flowers to be more difficult to cultivate, due to the inability of the dioecious plant to self-fertilize. Common examples of an imperfect flower that is monoecious are corn, birch trees, and walnut trees, while common dioecious plants include holly, willow trees, and poplar trees.