We often get asked to clarify the difference between annual, perennial, and biennial as people pick out their plants. Here is an explanation of those terms for gardeners here on the Seacoast in gardening zone 5-6. When looking at the entire life cycle of a plant, from seed germination to demise, plants are often in one of three categories:
Annuals
An annual is a plant that’s entire lifecycle happens during one year, also called a growing season. Some plants are used as annuals in New England, but would thrive as perennials in warmer climates, so you may see Northern garden centers labeling plants according to our zone. Gardeners value annuals for their prolific flowers or other showy attributes, in order to pump up drama in their landscape. It’s also fun to choose different annuals every year, and play with different colors and styles. They are also excellent choices for containers and window boxes. Annuals in our Seacoast zone include Pansies, Marigolds, Snapdragons, Petunia, Geranium, Zinnia, Begonia, Calibrachoa, Coleus, and many Tropicals.
Perennials
A perennial is a plant that will live for more than two years. Some perennials live for decades, and may even outlive you (some Peonies can live more than 100 years, for example). Others, known as short-lived perennials, only live for 3-5 growing seasons but lose strength and expire after a few years (some Delphineums fall into this category). Herbaceous perennials die back to the ground every year, and sprout up with fresh new growth the following year. Woody perennials do not die back to the ground entirely, and grow from established stems the next year. A tender perennial is one that straddles the line in its ability to survive in a particular gardening zone. Some gardeners have microclimates in which the plant is able to survive year after year, while another gardener finds that the plants dies every single year. Gardeners love perennials for their longevity, and for creating a reliable, long-term framework of colors and textures throughout their landscapes, and to backdrop showy annuals. And a major benefit of growing perennials is that you do not need to buy new ones every year.
Popular perennials include Rose, Peony, Lavender, Daisy, Coneflower, Aster, Russian Sage, and Day Lily.
Note: Here’s an additional curve ball! Some plants, like Salvias, Geraniums, Mums, Rudbeckias, and Hibiscus, can be found in annual or perennial form. These plants have been cultivated to serve various purposes for gardeners, and can be found in many forms.
Biennials
Biennial means the plant’s entire lifecycle occurs within two years. The first year is about establishing its root system and systemic strength, often only appearing as a small rosette of foliage on the soil’s surface. The second year of growth is when a stem, flower, and seed are produced. Many biennials will drop seed that produce “babies,” and so you can enjoy a patch of self-sown plants every year, all produced from the original parent plant. This can make some plants appear to be perennial, but they are in fact the descendants of the parent plant. Popular biennials include Hollyhock, Foxglove, Verbascum, and Poppy.
Which Plants Should I Get?
Most gardeners buy a combination of annuals, long- and short-lived perennials, and biennials. This allows you to create a long-term landscape, but still have some flexibility to change it up as the years progress, and try new plants out as you go along. Ultimately, know your budget, and know how you want the garden to serve you. Do you want to plant only perennials in the front of the house and then not plant anything more for another decade? Or do you enjoy the process of tending to a variety of plants and trying new plants out every few years? Pick the plants that will suit your budget and needs, and enjoy the wide variety of options available to you.