Incomplete Flowers: Examples & Structure

Instructor: Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

Many people assume that all flowers have the same parts. In this lesson we will investigate incomplete flowers. We will see what makes a flower incomplete and look at common examples of them.

Structure of Incomplete Flowers

Structurally, flowers consist of four main parts: sepals, petals, stamens, and pistils. Any flower that does not have one or more of these parts is considered to be an incomplete flower.

Sepals are leaf-like, usually green, and form a circle around the flower stem beneath the petal. They function to enclose and protect the flower while it is developing. Petals are the leaf-like, usually colorful structures arranged in a circle around the top of the flower stem. Their primary function is to attract pollinators for the purpose of reproduction. Stamens are the male reproductive structures of flowers and pistils are the female structures.

This image allows us to visualize the sepals, petals, stamen, and pistil of a flower.
Image of a flower

Examples of Incomplete Flowers

Any flower missing one or more of those four crucial parts is considered to be incomplete. There are many examples of incomplete flowers, including squash plants, sweet corn, American holly, and most grasses.

You may have grown traditional squash in your summer garden. As the plant grows and prepares to make its fruit it must undergo fertilization. For fertilization to take place, the squash plant must produce a flower. If you closely examine the bright yellow flowers of squash plants, you will notice that some of the flowers have stamens but no pistils and others have pistils but no stamens. This means that some of the flowers on the squash plant are male and some are female. This also makes them classic examples of incomplete flowers because each flower is lacking either the male or female structure.

This female squash flower is considered incomplete because it does not have stamens.
Picture of a squash flower.

Sweet corn is another common plant in most gardens. These tall plants that tower over most others in the garden are adapted for wind pollination. This means they do not really have a need for brightly colored flowers to attract pollinators. As a result, the flowers of corn plants do not have petals. This lack of petals means that corn is considered an incomplete flower.

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