One of the first things you learn as a new gardener is the difference between annuals and perennials in cold climate gardens—and what to expect from them. In most instances, annual plants last just one growing season while perennials will survive for years to come.
Once you know your plant hardiness zone, you can check the zone listed on plant tags to see if the plant will be tender or hardy in your area.
Understanding Annuals Versus Perennials
For those of us with cold climate gardens in the United States and Canada, plant nurseries often divide the shopping sections into annuals and perennials.
This basic way to group plants is very helpful for the gardener, basically telling us whether we can expect the plant live for just one season or more.
There are exceptions (described below). Here is a general overview:
Plant Life Cycles
- Annuals complete their life cycle in one growing season. The term is used both for plants that only have a one-year life cycle and for plants that could live more years in warmer places, but not where you live—which usually means they are not frost-tolerant.
- Perennials have a multi-year life cycle and, if suited to our hardiness zone, will go dormant in the winter and resume growth in spring—year after year.
- Biennials take two years to complete their life cycle (from germination to seed production). Grown as vegetable crops, we treat them as annuals and harvest them in the first year. Grown for flowers or seed production, we leave them for the winter and a second year of growth.
Once you know the basic distinctions, it’s good to double-check the plant tag or seed packet for specific details or do a little extra research.
For example, some plants sold as annuals are actually long-living and can be kept beyond our growing season with a little extra care while others are short-lived.
Plus, the same species, like lavender, can have annual and perennial varieties. It’s easy to buy the wrong type if you’re not checking the plant tag carefully.
- What Are Annuals?
- What Are Biennials?
- What Are Perennials?
- Differences Between Annuals & Perennials
- Same Species—Different Life Cycles
What Are Annuals?
Annual plants, also called “annuals,” complete their life cycle (from germination to seed production) within one growing season and then die.
An annual plant may be tender or hardy (somewhat or entirely), and short or long-living (weeks, months, or years). Also, some plants sold as annuals are actually tender perennials.
There are exceptions to these annual sub-categories so be sure to check your seed packet or plant tag for recommended growing conditions.
Annual Flowers & Foliage Plants
For those of us in cold climates, ornamental, flowering annuals are so popular because they provide an abundance of vibrant, showy flowers with continuous blooms from spring to fall.
These are plants often sold in ready-to-display hanging baskets, decorative pots, and multi-pack trays for transplanting as bedding plants. They are the thrillers, fillers, and spillers—all sorts of flowers, along with decorative foliage plants, and vines—providing instant and reliable beauty throughout the growing season.
Most of these annuals are non-native species that originate in warmer or tropical climates. There are hardy and native annuals as well—but the tender, non-hardy ones are the most popular.
Based on the abundance at plant nurseries, it’s a safe bet these plants are the bulk of seasonal revenue.
Many of our vegetable plants are annuals or we grow them as annuals.
In cold climates, slower-growing fruiting vegetables like squashes usually need a head start with indoor seed sowing (before last frost in spring) so, when transplanted outdoors, they are far enough along to be able to produce fruit before fall.
Tender annuals cannot tolerate frost. This group includes most of the annual, ornamental flowers sold at plant nurseries and grocery stores.
Hardy annuals like pansies and chrysanthemums (“mums”) are popular in spring and fall because they can tolerate light frost.
Other flowers like calendula or snapdragon may be labelled as “hardy annuals” or “cool flowers” because they prefer cooler temperatures but do not tolerate frosts. Hopefully the plant tag information makes the distinction.
This group tolerates some frost but not as much as hardy annuals.
Long-Living Annuals & Tender Perennials
Some annuals are long-living and could survive beyond the summer if they were not sensitive to cooler temperatures. You may also see them called tender perennials.
- Tomatoes are a good example. As fall draws near, I take cuttings from my outdoor tomato plants and grow them indoors where they eventually flower and fruit. It’s much slower and less prolific than outdoor growing, but it works. I’ve got a few that have been back and forth between indoor and outdoor growing for years.
We treat begonias and pelargoniums (commonly called “geraniums”) as annuals but both can last for years if protected from winter freezes by “overwintering” them. This shows four ways to overwinter geraniums.
- Pelargonium (“geranium”), not to be confused with perennial, hardy geraniums
What Are Biennials?
Biennial plants or “biennials” are flowering plants that take two years to complete their life cycle from germination to seed production.
Generally, vegetative growth (roots, stems, leaves) takes place in a biennial plant’s first year and flowering occurs in the second year.
In between, vernalization—a cold treatment naturally provided by winter conditions—is required to ready the plant for flowering and seed production.
Due to the two-year cycle, we leave ornamental, flowering biennials in place in the garden (without cutting them back) to provide vernalization and allow self production and self-seeding in the second year.
- Black-eyed Susan (Rudbeckia hirta)
- Foxglove (Digitalis)
- Great or common mullein
- Sweet William (Dianthus barbatus)
If growing for food, we treat biennial vegetables as annuals and harvest them in the first year.
If growing for seeds, you skip harvest and allow the plant to carry on to year two for flowering and seed production.
- Cabbage (some, not all)
- Onions including leeks (some, not all)
What Are Perennials?
A perennial is a plant with a multi-year lifecycle. In a cold climate, perennials go dormant in the winter and resume growth in spring when light and warmth returns.
While, technically, trees are perennials and plants like roses are “woody” perennials, when people talk about perennials they’re usually referring to herbaceous (non-woody) plants.
Herbaceous perennials are plants that “die back” in fall but do not die. Above ground the current year’s stems and leaves die off, becoming dry and brittle, turning various shades of brown or tan, but below the surface, within the soil, the roots remain alive and well.
While that dry, old growth can be removed in autumn, it is so ecologically important to animals (insects, birds, mammals, and more) for food and habitat that it’s best left in place until new growth is well underway the following spring or summer.
Depending on the species and growing conditions, a perennial may live for several years or longer. There are also many ways to propagate perennials for more plants.
- Anise hyssop
- Bee balm (Monarda)
- Blazing star
- Blue lobelia
- Blue wild indigo
- Blue stem goldenrod
- Bottle gentian
- Foam flower
- Joe pye
- Rose mallow
- Smooth oxeye
Differences Between Annuals and Perennials
Flowering annuals tend to have showier, more vibrant blooms (a common trait in warmer and tropical climates) that last an entire growing season—but that’s it. That same plant won’t regrow next year.
Flowering perennials are often subtler in color and form and bloom for shorter periods—sometimes just days or weeks. While less showy, the do return to bloom again year after year.
In the short-term, annuals tend to be lower in price than perennials, presumably because they are faster-growing (use fewer greenhouse resources), sell more by volume, and can be heavily discounted by retailers as time runs out.
Perennials tend to be pricier upfront but, with their multi-year lifespan and ability to spread, are more economical overall. And less waste scores more environmental points.
This shares garden mistakes that waste money including using up the budget on the allure of annuals when perennials will do so much more in the long run.
Seed Sowing & Saving
You can grow both annuals and perennials from seed. While either type of seed can be started indoors, annuals often need this head start to flower or fruit in the available timeframe.
Biennials like foxgloves or hollyhocks can be cost-effective (and gorgeous), providing blooms for many years, if allowed to self-seed in favorable growing conditions.
Some flowering annuals with shorter lifespans will go into seed production within the confines of our growing season. Others will be cut off by fall frosts.
Herbaceous perennials, particularly those native to or well-adapted to our climate, will set seed before winter if the flowers are not removed.
Native Versus Non-Native
In general, most plants sold as “annuals’ in local plant nurseries are non-native species.
Perennials can be non-native or native or some derivative (nativars, hybrids, and so on).
Same Species—Different Life Cycles
You cannot tell if a plant is annual or perennial by species alone.
Lavender is a good example of this—and gardeners get fooled by it over and over again.
We see “lavender” on the tag and, knowing there are perennial lavenders, assume they’ll come back each year—but some do not.
- Lavandula augustifolia, also called English lavender, can survive as a perennial in hardiness zones 5 to 9.
- Lavandula stoechas, also called Spanish, French, or Italian lavender, depending on the marketing location, is not cold tolerant and is sold as an annual.
There is a complete guide to identifying and choosing lavender here.
Did your houseplants spend the summer outside? See How To Bring Plants Indoors For The Winter for tips on preparing your tender plants for life in your home.
Find Your Frost Dates & Hardiness Zone
- Plant Hardiness Zones | United States | Canada
These are listed on seed packets and plant tags to guide your choices.
- Average Frost Dates | Use this calculator at Almanac.com. Enter your city and state or province to find your first and last frost dates and number of frost-free days.
- Tips: Understanding Frosts & Freezing For Gardeners
Mail Order Seeds
- SeedsNow | Botanical Interests United States
- West Coast Seeds Canada
Propagation How-to Books
These are books I like for plant propagation tips and tutorials:
- AHS Plant Propagation | American Horticultural Associate
- Grow Your Own Garden | Carol Klein
- Plant Propagator’s Bible | Miranda Smith
Seed Starting for Beginners
Sow Inside Grow Outside
by Melissa J. Will
NEW EDITION | Everything you need to get started with indoor seed starting for indoor and outdoor plants. Grow what you want—any time of year!
About This Ebook | Visit Ebook Shop
This ebook is a digital file (PDF format) you save to your device. It is not a physical product.
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