Picking out pretty plants for your fresh garden can be tons of fun, but what do those plant labels mean? The difference between annual, perennial, and biennial plants comes down to how many years they live. Annuals live for one year, biennials live for two years, and perennials live more than two years — from three years to hundreds of years.
While it can be tempting to plant all annuals for an immediate explosion of color or only plant biennials and perennials because they live longer, the secret to long-term garden success is planting all three varieties. They each have their own garden superpowers.
Let’s dive into what defines these three plant types, some common varieties, and how to care for them.
- How to care for annuals, perennials, and biennials
- FAQ about annual, perennial, and biennial plants
- You have so many plant choices
Annuals don’t waste any time when it comes to giving your yard a spectacular flower show. They complete their entire life cycle in one growing season (spring to fall), germinating in the spring, blooming in the summer, and releasing seeds and dying in the fall. Not only are annuals gorgeous in your garden, but they make beautiful cut flower arrangements to display at the kitchen table or bring to your friends.
A common misconception about annuals is that they’re “one and done:” Once you’ve enjoyed one season of them, they’ll never come back. In reality, many annual plants (like poppies, cleome, snapdragons, cosmos, and amaranth) release thousands of seeds before they die. So although your original plant will die, fresh new seedlings will emerge next year.
Types of annuals
Annuals fall into three major categories:
Most annuals can grow across the country, from USDA hardiness zone 2 (far up North) all the way to zone 11 (way down South). The “tender,” “hardy,” and “half-hardy” labels distinguish when plants should be planted, when they will die, and whether they can survive the frost.
Tender annuals, also known as summer annuals, love the heat and die when the first frost arrives. These warm-season, heat-resistant plants thrive in warm soil and air and have a very low tolerance for cooler fall temperatures.
Plant tender annuals in spring, two to three weeks after the final frost date.
Popular tender annuals:
- American marigold
- Annual geranium (Pelargonium spp.)
- Sweet basil
- Garden balsam (Impatiens)
- Mexican sunflower
Hardy annuals, also known as winter annuals, are the most frost-tolerant annuals, giving your lawn a pop of color in late fall and winter when other plants have died. They can withstand cold weather, cold soil, and light frosts without being damaged. The trade-off? They aren’t as heat-tolerant as tender annuals and may wither and die in summer when temperatures get too high.
Plant hardy annuals in fall, six weeks before your area’s first fall frost date, or early spring, four weeks before your area’s final spring frost date.
Popular hardy annuals:
- Annual verbena
- Dusty miller
- Ornamental cabbage
- Pot marigold
- Sweet alyssum
Half-hardy annuals aren’t as cold-resistant as hardy annuals, but they can still tolerate cool soil and air. They’re susceptible to frost damage and won’t last as long into winter as hardy annuals, but they’ll give your yard a few more weeks of fall foliage than tender annuals.
Plant half-hardy annuals two weeks before your area’s final spring frost date.
Popular half-hardy annuals:
- Annual baby’s breath
- Annual cosmos
- Annual dianthus
Perennials grow strong year after year. While annuals die when the frost hits or during the cold winter months, perennials store up their energy and go dormant during the winter, waking up in spring.
For the first two years, perennial plants focus their growth below the soil surface, digging deep into the ground for a dense, established root system that can handle hard, frosty soil. This ensures long-term success, but it also means that most perennials don’t expend their precious energy blooming in the first year. You’ll have to wait until the second or third year for blossoms to appear.
That’s why it’s important to plant annuals alongside perennials in a new garden. You don’t want to wait two years for flowers to bloom!
Types of perennials
Perennials come in all shapes and sizes, from trees and shrubs to flowers, ornamental grass, and ground cover. Horticulturalists classify perennials into two categories:
1. Woody: Trees and shrubs with tough brown stems; plants grow larger each year and do not experience seasonal dieback
2. Herbaceous: Low-growing plants with soft, green stems; the top portion of the plant dies in fall and winter and grows back in spring
For gardening purposes, perennials can be classified like annuals as tender, hardy, or half-hardy, depending on their resistance to the cold.
Tender perennials, also known as summer perennials, grow as evergreens in warm southern climates, but they do not respond well to frost and require special care if grown in cooler northern regions. Typically, these plants thrive year after year in USDA hardiness zones 10 and 11 but die when the cold weather hits in cooler zones above Georgia and northern Texas.
If you live in the upper two-thirds of the country, you can plant these pretty bloomers in containers and bring them indoors before the first frost or you can grow them as annuals.
Because tender perennials behave like annuals in the majority of the country, they are often referred to as annuals.
Plant tender perennials in spring after the threat of frost has passed.
Popular tender perennials:
- Black-eyed Susans
- Calla lily
- Tropical hibiscus
Hardy perennials (aka winter perennials) are tough-as-nails plants that overwinter in snowy, icy, and freezing conditions. In cold climates, they stop growing in the winter and perk up in spring. In warmer climates, they grow as evergreens. Most hardy perennials grow in USDA hardiness zones 3 through 9.
Plant hardy perennials in early fall to give them time to germinate before temperatures drop.
Popular hardy perennials:
- Blanket flower
- Butterfly weed
- Coral bells
- Eastern bluestar
- Ox-eyed daisy
- Shasta daisy
- True geranium (Geranium spp.)
Half-hardy perennials can withstand frost and freezing temperatures, but they are not as cold-tolerant as hardy perennials and may be damaged by extreme cold. These perennials grow well in the middle portion of the U.S., typically from hardiness zone 4 to zone 9 (though it varies by species). They aren’t suited for the far North.
Plant half-hardy perennials in spring after the threat of frost has passed.
Popular half-hardy perennials:
- Carpet sedum
- Creeping phlox
- English lavender
- Purple coneflower
As the name suggests, biennials take two years to complete their life cycle. They spend their first year establishing roots, foliage, and food structures and their second year flowering, producing fruit, and releasing seeds before dying.
Biennials are typically more cold-hardy than annuals. In fact, the winter chill triggers their ability to bloom the next season. Many tasty veggies like kale are biennials, in which case you’ll harvest leaves in the first and second seasons before letting the plant go to seed.
Biennial plants can be tricksters: Some may not survive the first winter, some may bolt (experience their full life cycle in just one growing season), and others may live longer than two years. In general, though, you can expect plants to die in the fall of the second year and new seeds to germinate the following spring.
Plant biennials in early spring to give their roots time to establish before being exposed to the hot summer sun.
- Canterbury bells
- Evening primrose
- Sweet William
- Swiss chard
How to care for annuals, perennials, and biennials
We’ll start with some general guidelines for plant care, and then move into the watering schedule for each plant type.
Plant care tips
- Water deeply to encourage long, strong roots. Shallow waterings encourage roots to stay at the soil surface, which causes plants to dry out and die during drought.
- Use a soaker hose or drip irrigation system, rather than sprinklers, to deliver water directly to the plant roots. This minimizes the potential for water to evaporate before reaching the roots.
- Fertilize annual seedlings to start them off strong. Use a complete nitrogen-phosphorus-potassium (N-P-K) granular fertilizer or soluble fertilizer that is mixed with water.
- Apply organic mulch around plants to protect roots, keep the soil moist, and give plants a nutrient boost. Spread a layer of pine needles, shredded leaves, or compost around your perennials and biennials. Spread a light layer of grass clippings around your annuals.
- Weed by hand once a week or as needed to keep garden beds healthy and prevent weed roots from stealing valuable nutrients from your plants.
- Deadhead spent flowers to encourage new growth, but allow the last flowers of the season to go to seed for fresh seedlings next spring. Cut back your annuals in midsummer to prevent them from getting scraggly.
- Clip the top growth off of perennials and biennials during the growing season to encourage bushy, dense foliage. This process is known as “pinching.”
- Stake tall annuals like cosmos to keep them upright. Stakes should be about 6 inches shorter than the mature plant to not distract from the plant’s natural beauty.
- Prune plants to remove diseased branches and foliage and ensure adequate spacing between plants.
Watering schedules vary depending on how drought-tolerant your plants are, so check your plant’s specific water needs. Here are the general guidelines for watering your annuals, perennials, and biennials.
|— Check soil moisture levels daily and water thoroughly if the soil is dry. Do not wait for annuals to wilt before watering them.
— Most annuals need at least 1 to 1.5 inches of water per week, and more may be needed in hot, dry weather.
|— Water daily for the first two weeks after planting.
— Then, transition to a schedule of two to three times per week for the first year. Wait until the soil dries out before watering to encourage roots to dig deep into the soil.
— In the second year and beyond, water perennials once or twice a week for a total of 1 inch of water.
|— Water biennials daily for the first two weeks after planting. Then, transition to once a week in the cool spring weather and up to three times per week in the summer heat, keeping the soil moist (but not wet, as soggy soil can cause root rot).
— Biennials typically need 1 to 1.5 inches of water per week.
FAQ about annual, perennial, and biennial plants
In general, annuals require the most care of the plants in your garden. Because they’re only here for one season, they don’t expend energy growing deep roots, and they’re often non-native, which means they aren’t adapted to your particular climate and soil type and will require more fertilizer.
Perennials need TLC for the first two years, but once they’re established, they require the least maintenance of the three plant types, especially if they are native to your region. Biennials require less maintenance than annuals but more maintenance than perennials.
It depends on the type of perennial. Some flowers like columbine and blanket flower last only three to four years before they require reseeding, while shrubs like Adam’s needle may last 40 to 50 years and trees like ginkgos may live for hundreds of years. (The oldest ginkgo is over 3,000 years old!).
Fill the majority of your garden with perennials, and plant annuals and biennials as supplemental color. Though perennials take longer to establish, they typically require less water and maintenance than annuals, and they attract more pollinators for an eco-friendly landscape. Plus, having more perennials means fewer trips to the garden store for new plants.
A native species is a plant that’s specifically adapted to your region, so it’s an expert at handling your climate, terrain, and weather. For example, plants native to the Southwest thrive in sandy soil, hot summers, and drought conditions, whereas plants native to the East Coast grow in heavy clay soils, survive the four seasons, and stand up to hurricane winds.
You can find recommended native plants by state using the Lady Bird Johnson Wildflower Center’s search tool. Your local university’s cooperative extension program is also an excellent resource for information on native plants. Many universities and botanical gardens offer guidebooks and lists of native plants for your state or region.
Cut the seed heads off your plant immediately after the flowers bloom. There’s no guarantee that your biennials will grow past the two-year mark, but this nifty trick (known as deadheading) redirects the plant’s energy from seed production to root and foliage growth. That means your plant has more energy to grow for an extra season.
You have so many plant choices
Annuals, perennials, biennials, oh my! Planting a garden can be a fantastic family experience, but maintaining healthy blooms year after year requires consistent care. Even the toughest plants need to be trimmed and pruned, and weeding and fall cleanup are a must.
If you want to put the hedge clippers down and take a breather, call a local lawn care pro to handle all your lawn care needs.
Main Photo Credit: JillWellington | Pixabay