By Dr. Leonard Perry, Extension Professor
University of Vermont
Why is it important to learn how garden flowers are grouped or classified?
For one, it will make it easier for you to order plants and flowers. You also will better understand terms you see in books and catalogs. And you'll learn about some of the cultural or growth factors to consider when selecting flowers for your particular garden.
To begin with, flowers and plants can be classified or grouped many different ways, depending on your perspective. Botanists may be most interested in flower structure and plant family relationships. Horticulturists, such as myself, are more interested in the correct names for flowers, their growth cycles, and their cultural requirements.
So let's take plant names first. You probably know that plants have common and scientific names. The latter is based on Latin, and consists of two main parts--the genus first and then the species name. This "binomial" system of nomenclature (plant names), as it is called, was first developed by the Swedish botanist Carl von Linnaeus (1707-1778).
There are many other subdivisions of the species, just as on the other end genera are grouped into families (usually with similar flower characteristics). The main subdivisions gardeners are interested in are the species breakdowns into either varieties or cultivars. The word "cultivar" is confusing to some, but it just refers to a cultivated variety--one arising out of human cultivation. Cultivars usually only differ in one main characteristic, such as growth habit, flower color, height, or similar.
Common names often are easier to understand and pronounce, so most people use them. But when I refer to Spurge, am I talking about Euphorbia or Pachysandra? This potential confusion, even among different common names in different regions and countries, is why scientific names are needed as well.
The second way flowers can be grouped or classified is by growth cycle. In other words, how many years does it take for them to complete one cycle from seed to flower. If the cycle is finished in one year, then they are called "annuals." If completed in two years, often flowering in the second, they're "biennials." And if they just keep coming back and blooming each year (provided they're hardy of course!), they're "perennials."
Then there are the bulbs, corms, and tubers--those perennial flowers (some are hardy, some tender) arising from specialized roots. Of course, the perennials can be divided further into many specific groups, either by growth habit such as the ornamental grasses, or growth environment such as aquatic plants.
The third method of classification, and the one most important for gardeners, is by growth habit and cultural preference. Factors included here, and ones you should consider when both choosing perennials and placing them in your garden, include: