Anyone who has ever stopped to smell the flowers has likely noted some of the differences among them such as color, shape or fragrance. Of course every type of flowering plant produces a flower type inherent to its family, genus, or species and different plants flower at different times of the year.
Did you know, however, that botanists, researchers, and other horticultural professionals further distinguish flowers in myriad different ways than the average “flower sniffer” has probably never considered?
All flowers, regardless of their species fall into some combination of the following categories:
Complete Flower - Complete flowers are those that possess all of the following plant parts: petals, pistil, sepals and stamen. Sepals are the base of the blossom and are often, but not always green. Petals surround the reproductive portions of the flower. Stamen are the male components and the pistil is the female element of the flower.
Incomplete Flower - An incomplete flower is one that lacks one or more of the components that comprise a complete flower.
Perfect Flower - A perfect flower contains both male (stamen) and female (pistil) components. Perfect flowers are also known as bisexual flowers, hermaphroditic or androgynous flowers.
Imperfect Flower - An imperfect flower is one that lacks either male or female components.
Pistillate Flower - A pistillate flower is one that possesses only female (pistil) components. These include ovaries and stigma where pollen is collected or captured.
Staminate Flower - A staminate flower is one that possess only male (stamen) components. These include the filament and the anther where pollen is produced.
Unisexual Flower - Unisexual flowers are those that are either male or female and can either exist on the same plant or on male or female plants of the species. A unisexual flower is a type of an imperfect flower.
Composite Flower - Composite flowers are those that are comprised of two separate types of flowers on the same blossom; the disk flower and the ray flower. They are sometimes referred to instead as “compound” flowers.
Disk Flower - A disk (sometimes “disc”) flower is the inner blossom of a composite flower. Think of the “black eye” in black-eyed Susan or coneflowers.
Ray Flower - Ray flowers surround disk flowers on composite blossoms. Think of the petals that surround the “black eye” in black-eyed Susans.
Umble Flower - Umble flowers are multiple flowers that emanate from a single point to form a single blossom, so named as they are like the “ribs” of an umbrella, which come down from a fixed, center point. Umble flowers can be either simple or compound.
Double Flower - A double flower is any blossom that has more than one layer of petals, resulting in a fuller appearance. Double flowers are usually sterile, as the reproductive elements are not easily accessible to insects or pollinators in double flowers. Most cultivated rose species are double-flowered. Semi-double flowered plants also exist.
Actinomorphic Flower - Also known as “regular”, “radial” or a “polysymmetric” flower, actinomorphic flowers can be bisected at any point and have two identical halves. Most flowers are actinomorphic.
Zygomorphic Flower - Also known as an “irregular”, “bilateral”, or “monosymmetric” flower, zygomorphic flowers are those that are symmetrical on only one axis.
Most five-petaled flowers fall into this category; they can be halved on one plane and have two equal parts, but not on a plane perpendicular to the bisected halves. Orchid flowers are a good example of this type of flower:
Raceme Flowers - Raceme flowers grow without a center “branch” in a spike-like shape and bloom from the bottom to the top. Panicles are racemes that do emanate from a center branch.
Catkin Flowers - Best epitomized by the pussy willow, a catkin is a flower spike without petals comprised of numerous unisexual flowers. Though not true for all species, catkins are often male flowers.
This is not an exhaustive list, but represents some of the more common distinctions among flower types.
Many of these types can be further subdivided based upon other characteristics and variations of the sepals, petals, stamen, pistil, or other factors relating to how they develop from a plant’s stem, or other variables both seen and unseen.