Definition - What does Incomplete Flower mean?
A flower lacking one or more of the normal flower parts (the male (stamen), female (pistil), petals, and sepals) is called an incomplete flower.
Incomplete flowers lack in at least one of the four floral parts. A flower with only a calyx, corolla, and androecium is an incomplete male flower, whereas, a flower having gynoecium instead of androecium, along with a calyx and a corolla, is an incomplete female flower.
There are many examples of incomplete flowers, including squash plants, gourds, sweet corn, American holly, and most types of grasses.
Incomplete flowers should not be confused with imperfect flowers.
MaximumYield explains Incomplete Flower
While an imperfect flower consists of only the male or female part (stamen or pistil) and may or may not contain sepals or petals, an incomplete flower is missing one or more of the four main flower parts, which are the male (stamen), female (pistil), petals, or sepals.
Incomplete flowers are without one or more of the normal parts, as carpels, sepals, petals, pistils, or stamens. The 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's developing.
The flowers’ petals are the leaf-like, usually colorful structures arranged in a circle around the top of the flower stem. The primary function of the petals is to attract pollinators (bees and other insects) for the purpose of reproduction. The stamens are the male reproductive structures of flowers, and the pistils are the female reproductive structures. Any flower missing one or more of those four crucial parts is considered to be incomplete.
Some incomplete flowers possess both sets of sexual organs, and are considered 'perfect'. Thus, these incomplete flowers have a simple perianth consisting of only a calyx (but no corolla), or the perianth is lacking entirely.
Some examples of ‘perfect’ (hermaphroditic), but incomplete, flowers are below and rue-anemone. This is a spring wildflower that is easily confused with Isopyrum biternatum (false rue-anemone).