By Dr. Leonard Perry, Extension Professor
University of Vermont
You've probably seen terms in books, magazines, and catalogs, such as "corm," "corolla," or "panicle." Do you know what these mean? If not, then you don't have a total understanding of the plant you're reading about or are thinking about buying. You may end up with a surprise--a plant you don't really like or one that you don't know how to care for properly.
Roots are probably the least known parts of flowers, mainly because they're out of sight, so out of mind. But they can be the most crucial to the success of flowers. Most flowers have fibrous roots--a network of many fine roots. Those adapted for poor soils and dry habitats have taproots--long and deep roots that are designed to go deep in search of water and nutrients. Those with taproots like baby's breath may be hard to transplant and divide.
Then there are the specialized roots such as bulbs, corms, and tubers. These are special overwintering structures that store plant nutrients. They may be tender and sensitive to severe cold. Bulbs like daffodils are actually short underground stems surrounded by the fleshy scales that store food.
Corms are swollen underground stems, broader than they are high. Two examples are crocus and gladiolus, the latter needing to be dug up and brought in for winter in the colder regions like Vermont. Tubers, like dahlias, are thickened underground stems. This particular plant also needs to be dug up for the winter. Rhizomes are creeping underground stems, partially or totally underground. A good example is the bearded iris.
And then there are shoots. For most garden plants, shoots grow from the tips. Prune them, and they branch or send up new shoots. Grasses, however, grow from the base. Prune them, and they keep growing, just as your hair does.
Flowers are the most complex. The key flower parts are the petals, which together form the "corolla." These often have other structures on the outside, like petals but less showy, called "bracts." Together they are called the "calyx." "Stamens" are the male parts producing the pollen. The "pistil" is the female part producing the seeds.
If all these parts are in each flower, they're said to be "complete." If they have the male and female parts in the same flower, they're said to be "perfect." But sometimes flowers only have one sex--they're either male or female, unisexual, or "imperfect."
If these unisexual flowers are on the same plant, the plant is "monoecious," meaning one house. If they are on different plants--one plant is male, the other female--they are "dioecious." This is important to know, especially if you are looking for cross-pollination and fruit for an interesting landscape effect or for eating!
Flowers are either single (like most roses), or grouped together into "inflorescences" as with most garden flowers. The terms for these inflorescences--loosely referred to as "the flowers" by most gardeners--are what you usually see in descriptions. Some of the more common include "spike," indicating individual flowers attached directly to a stalk, and "raceme," flowers on short stems attached to the main stalk. If the raceme is branched, it's called a "panicle." If the panicle is flat-topped, it's a "corymb."
"Umbels" refer to species with individual flowers, usually very tiny, on short stalks arising from a single point. Some good examples are Queen Anne's Lace and other members of the carrot family. If the stalks are almost non-existent, the flower is a "head" as with Scabiosa.
Many of our garden flowers are in the aster family, characterized by "composite" flowers--those with two actual flower types. The outer are the showier "ray" flowers. The inner head or button is called a "disc" flower.
The next time you see a garden mum, aster, or sunflower, think of each of those "flowers" as really being hundreds of smaller flowers, each capable of being pollinated and forming a seed. That's what makes plants so amazing!