Garden Jargon Made Simple

Simple definitions for common gardening terms.

We've assembled this glossary of 37 gardening terms you're likely to encounter at garden centers and in catalogs, and defined them in our usual accurate yet crystal clear, gardener-friendly way. 
Annual: This type of plant has its complete life cycle, beginning from a seed and producing new seed for a succeeding generation, during a single season and then dies at the end of that season. Marigolds and zinnias are annuals many of us have grown. 
Biennial: It takes this type of plant two seasons to go from seed to seed, like hollyhocks and foxglove, develop roots and leaves during their first growing season and then grow flowers and set seed during the second year. Biennial plants die at the end of their second season. 
Bracts: On most of the plants we grow for their appearance (rather than for food or fiber), the blossom—the part of the plant that contains its reproductive organs—is the main attraction. But on certain plants it is the colorful leaves surrounding the flower that attract us. Those leaves are called "bracts." The most familiar example of this is on the poinsettia, notes Gus De Hertogh, Ph.D., professor of horticulture at North Carolina State University. "The little yellow, egg-like things in the center of those colorful leaves are the flowers on the poinsettia," he elaborates. "But those colorful leaves known as bracts are what we grow them for." 
Bulbs: "Any plant with an enlarged underground storage organ can be called a 'flowering bulb,'" says Gus De Hertogh, Ph.D., professor of horticulture at North Carolina State University. But botanists and others who are sticklers for detail do distinguish between bulbs, corms, rhizomes, tubers, tuberous roots and hypocotyls—all of which produce geophytes, or plants with (here we go again) enlarged underground storage organs. What is being stored? "The nutrients the plant needs to grow each year," Dr. De Hertogh answers. "After a flowering bulb finishes blooming for the year, its energy is devoted to storing those nutrients for the next season in the bulb." That's why you must let the leaves stay on tulips, daffodils, lilies and other flowering bulbs after they're done blooming; if you cut off the leaves, the bulbs have no way to collect sunlight and convert it into food for next year's blooms. 
A bulb, strictly speaking, has enlarged scales where most of those nutrients are stored and a small basal plate, which is where the next season's roots and shoots are. A corm is just the opposite: it has small scales and the nutrients are stored in the enlarged basal plate. Rhizomes and tubers are two different types of enlarged stems, which store the nutrients. Tuberous roots are (no surprise) enlarged roots serving as storage organs. A hypocotyl is like an oversized seed, where the nutrients are stored in enlarged cotyledons. 
Cotyledon: Seeds of all sizes contain the nutrients they need to get growing—those nutrients are stored inside the cotyledon (pronounced cot-el-LEE-dun), which are wrapped around the embryo within the seed. "In many plants, the cotyledon opens up to form transitionary leaves—the small, rounded leaves you see when the seed has first sprouted--which then fall off after the plant has developed more permanent leaves," observes Richard Racusen, Ph.D., professor of plant biology at the University of Maryland. "But in all plants that grow from seeds, the cotyledon's critical role is as the structure that stores the nutrients the plant uses to germinate." 
Crown: Simply put, a plant's crown is the spot where its roots and stems meet. If you get a plant, like an astible or a peony, that comes with the recommendation to "bury the crown," be sure to completely cover the roots with soil, but leave some of the stems poking up through the soil, advises Gus De Hertogh, Ph.D., professor of horticulture at North Carolina State University. 
Cultivar: The quick answer to the question "What is a cultivar?" is to say that it's the proper term for what we usually refer to as a "variety." Now, what exactly is a variety? "A plant that has been selected or bred to have a specific trait or traits different from other members of its species and that has been given a unique name," responds Nona Koivula, executive director of All-America Selections, an organization that coordinates annual trials of new cultivars and then awards its AAS designation to the winners of those trials. 
An example might be the best way to make the concept of cultivars clear: 'Elizabeth Taylor' and 'Ingrid Bergman' are names of hybrid tea roses you may see at a nursery or in a catalog. They have similarly shaped canes and flowers, but Elizabeth Taylor's blossoms are deep pink while Ingrid Bergman's are dark red. Both are hybrid tea rose cultivars. Names of cultivars are typically designated with single quotations marks ('Elizabeth Taylor').