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Types of flowers
If a flower has a stamen, pistil, petals, and sepals, it is called a complete flower (Figure 19). Roses are an example. If one of these parts is missing, the flower is called incomplete.
The stamen and pistil are the essential parts of a flower and are involved in seed production. If a flower contains both functional stamens and pistils, it is called a perfect flower, even if it does not contain petals and sepals. If either stamens or pistils are lacking, the flower is called imperfect. Pistillate (female) flowers possess a functional pistil or pistils, but lack stamens. (Figure 20) Staminate (male) flowers contain stamens, but no pistils.
Plants with imperfect flowers are further classified as monoecious or dioecious.
Monoecious plants have separate male and female flowers on the same plant (e.g., corn and pecan). Some monoecious plants bear only male flowers at the beginning of the growing season, but later develop both sexes (e.g., cucumbers and squash).
Dioecious species have separate male and female plants. Examples include holly, ginkgo, and pistachio. In order to set fruit, male and female plants must be planted close enough together for pollination to occur. In some instances (e.g., holly), the fruit is desirable. In the case of ginkgo, however, the fruit generally is not desirable due to its putrid smell when ripe. Kiwis are complicated because they may have one plant with bisexual flowers and another plant with only male flowers. The plant world doesn't always have absolutes!
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