The Difference Between Perennial and Annual Plants

Whether you have a garden or you're interested in starting one, you're likely familiar with the terms annual and perennial. Both are used to describe the growing cycle of plants, but knowing the difference between annuals and perennials (and their lesser-known counterpart, biennials) will help you understand which is better suited to your gardening style and help you plan your yard's layout from season to season. It will also dictate the type of care your plants need at key points during the growing season.

Perennial Definition

Perennials are the gift that keeps on giving. "A perennial is a plant that lives more than two years and regrows each spring," says Jeff Lorenz, the founder of Refugia. While the blooms and leaves of perennials die back during winter, new growth arises the following spring with minimal work on your part. "When sited correctly, perennials can be divided and moved around the garden to create a lush and immersive landscape that will return year after year," says Lorenz.

Perennials are typically planted during fall or early spring. Common perennials include hellebores, peonies, forsythia, daylilies, poppies, black-eyed Susans, chrysanthemums, and hydrangeas.

Benefits of Perennials

The biggest allure of perennials is that you only have to buy them once, while annuals are purchased every year. "Perennials native to your location have the added benefit of providing specialized ecological functions, including being host plants for various types of insects," says Lorenz. Additionally, perennial seed heads left around through winter provide forage for wildlife and allow plants to self seed throughout the garden.

Although perennials flower for a shorter period of time than annuals, this gives you the opportunity to combine a more diverse mix of plants for extended and varying bloom times. "They are also deeply rooted and are wonderfully efficient at managing stormwater in a way that most annuals do not," says Lorenz.

Annual Definition

Annuals complete their life cycle in a single growing season and don't return again. "They are a great way to add color as well as texture to your garden in a near instant, as they tend to grow quickly," says Kieran Avis, horticulturist at Longwood Gardens. There are a few types of annuals you'll likely come across at your local plant nursery.

Cool-Season Annuals

As the name implies, cool-season annuals thrive in cooler temperatures and can be used to add interest to your garden during spring or fall. "Poppies, nigella, sweet peas, violas, and snapdragons are all great examples of cool-season annuals that will make your spring garden shine," says Avis. "With a little planning, an added benefit is that cool-season annuals will often complement your spring bulb display."

Warm-Season Annuals

Warm-season annuals, also referred to as tender annuals, enjoy the heat of summer. "Annual sunflowers, gomphrena, salvias, celosia, and zinnias are all great additions to make your summer garden standout," says Avis. Many tender annuals are native to the tropics, which is why they tend to thrive in warmer climates.

Self-Sowing Annuals

Self-sowing annuals regrow the following year from seeds, instead of from their roots like a perennial would. "Plants will drop seeds in your garden once they are planted and those seeds will germinate on their own the following year," says Avis. "Verbena bonariensis and some nicotiana are good examples of this."

Benefits of Annuals

Often showier and more colorful than perennials, annuals are a great way to add interest to your garden. "Annuals are also extremely versatile and can be used in containers, mixed borders, cutting gardens, or even hanging baskets," says Avis.

Biennial Definition

In addition to perennials and annuals, you should also consider biennials—though you'll have to wait a bit to enjoy them. "Biennials are plants that take two growing seasons to flower," says Avis. "They will send out herbaceous growth the first year followed by herbaceous growth and flowers the second year." After their second year of life, they die—putting them right in the middle of annuals and perennials. However, like some annuals, certain biennial varieties drop seeds, perpetuating their life cycle in your garden.

Common biennial plants include forget-me-nots, foxglove, and sweet William; several vegetables, including kale, Brussels sprouts, and cauliflower, are also biennial.

Benefits of Biennials

While you may feel impatient waiting for them to bloom, biennials offer the perfect mix of benefits. They regrow like perennials and are typically showy like annuals. "Biennials are another good tool to increase the beauty in your garden," says Avis. "It is important to supplement plantings yearly to ensure you have flowers every year, since biennials flower in their second season of growth."