When you’re beginning gardening, there are so many new terms to learn. One of the most important is the difference between annual and perennial plants.
Put simply, annual or perennial is a classification of how long your plant’s lifecycle is: 1 year for annuals, 3 or more years for perennials. Yet, some plants are grown as perennials in warm areas, and as annuals in cold areas. As with many things in gardening, the answer is, “it depends“.
What are annual plants?
Annuals are plants that grow from seed to flower to seed in one growing season and then die. All of the roots, stems, leaves and flowers die every year.
Yet, the plant may appear again in your flower or vegetable bed the following year, because its seed overwintered in your garden. But not all flower seeds will overwinter in your garden – only those plants adapted to your hardiness zone will produce seeds that survive your winters.
The annual category is divided into 3 types:
- Tender annuals have little to no tolerance for cold weather and thrive in warm temperatures.
- Hardy annuals have some tolerance to frost and cold weather.
- Half-hardy annuals have some tolerance to cold weather, but less so than hardy annuals.
In cold areas, some annuals like begonias must be brought indoors for the winter. If not, the cold temperatures will kill them. Where I live in Pennsylvania, Rosemary dies every winter, but in the southern U.S., will carry on indefinitely as my Sage does.
What are perennial plants?
Perennials are officially defined as plants that live at least 3 years – some have short lifespans and some carry on for decades. People refer to perennials as “plants that come back every year”. All trees, all shrubs, and some flowers are perennials. But generally, the term refers to non-woody plants like flowers (a woody plant is one that develops woody structures above ground like vines, trees, and shrubs.)
In most perennials, the top parts of the plant die back each winter and regrow the following spring from the same root system. If you grow Purple Coneflower in your garden, you’ve seen this (so don’t yank them out in the fall when they appear to be dead – they’re just dormant).
Some perennial flowers do keep their leaves year round. The same is true for perennial shrubs like certain viburnums that never appear to lose their leaves or only lose them for 2-3 months. A single columbine plant may only live for 3 years, but produces seed to produce many new plants. Peonies however, last for many years.
The perennial category is also divided into 3 types:
- Tender perennials grow year round in warm climates but must be overwintered indoors in cold climates. They are also sometimes called temperennials.
- Hardy perennials survive frost and cold weather without problems.
- Half-hardy perennials can tolerate some frost and cold temps, but not a deeply cold winter.
Some plants behave as an annual or perennial based on the local climate. For instance, Black-Eyed Susan and pepper plants are actually perennials and grow for many seasons in warm climates. In areas with cold winters, these plants last only one season unless they are overwintered indoors.
What are biennial plants?
Biennials are plants that take 2 growing seasons to complete their lifecycle. In the first season, only their foliage appears and grows near the ground. In the second spring, the stem elongates, flowers grow, seeds fall, and the plant dies. Canterbury Bells and Foxglove are perfect examples.
Are bulbs annuals or perennials?
Flowers that grow from bulbs are a specialized group of perennials that produce all foliage and blooms in one season and then appear to die, just as annuals do. But the perennial that grows from a bulb is simply winter dormant. The plant stores energy in the bulb to produce flowers and foliage again the following season, if cared for properly.