Annuals vs. Perennials: How to Choose the Right Flowers

Annuals vs. Perennials: The Core Difference

An annual lives for one growing season and a perennial lives for three or more years. University of Vermont Extension describes the annual life cycle in full: a seed is sown, germinates, grows, flowers, fruits, goes to seed and dies during one growing season. A perennial, in Purdue University’s definition, is a plant that grows for three or more years. Annuals such as petunias and zinnias bloom from spring until autumn frost, while most perennials bloom for a shorter period, often 2 to 8 weeks.

That trade explains almost every buying decision. Annuals give the longest show and have to be replaced every year. Perennials come back by themselves and spend most of the season as foliage. University of Maryland Extension notes that most perennials die to the ground with cold weather and come back again from their roots.

Common annuals named by Purdue and Maryland include petunias, marigolds, zinnias, impatiens, begonias, pansies and snapdragons. Common perennials include daylilies, hostas, peonies, purple coneflower, black-eyed Susan, coreopsis, bee balm, phlox and asters.

Two In-Between Groups: Biennials and Tender Perennials

Plant tags carry two more labels that confuse the simple split.

A biennial takes two years. Vermont’s description is that the seed germinates and grows foliage during the first year, and in the second year the plant flowers, produces seeds and dies. Hollyhock, foxglove and Sweet William are the examples Maryland gives. A biennial bought in leaf in spring may not flower until the following year.

A tender perennial is a true perennial that cannot survive your winter. Vermont explains that these plants thrive outdoors only in warmer climates and are often sold and treated as annuals in colder ones, with fuchsia as the example. Hardiness zones settle the question. A higher zone number means a warmer climate, so in Vermont’s words a plant suitable for zones 9 to 11 will not survive the winter in zone 4. Check the zone range on the tag against your own before paying a perennial price.

Among true annuals, the Royal Horticultural Society separates hardy annuals, which will germinate outdoors, from half-hardy and tender ones, which need extra warmth to germinate and are sown indoors in heat in early spring.

How Long Each Type Blooms

Bloom length is the biggest practical difference. Purdue states that annual flowers bloom from spring until autumn frost. Washington State University Extension adds a condition: annuals provide longer periods of color than most herbaceous perennials if the fading flowers are picked off so that the plant does not set seed. Our guide to deadheading flowers covers the technique.

Perennials vary widely. Washington State puts the range from short, less than one week for some peonies, to long, six weeks or more for yarrow. Alabama Cooperative Extension gives a general bloom time of 2 to 8 weeks for herbaceous perennials in that state, with a few standouts: Lenten rose at 8 to 10 weeks and Russian sage at 2 to 3 months. Maryland summarizes it as about a month for most perennials, and notes that some bloom 2 or 3 times a season if deadheaded. Washington State lists campanulas, coreopsis, daylilies, lupine, lavender and some sages among the perennials that send up new side shoots and more bloom after the first spent flowers are removed.

The answer to short bloom is to combine species. Purdue points out that planting several perennials with different bloom seasons can yield season-long color from a bed where no single plant flowers for long.

Side-by-Side Comparison

Factor	Annuals	Perennials
Lifespan	One growing season	Three or more years
Bloom period	Spring until autumn frost, with deadheading	Often 2 to 8 weeks; about a month for most
Winter	Die at the end of the growing season	Most die to the ground and regrow from roots
Purchase price	Tend to cost less per plant	Tend to cost more per plant
Repeat cost	Bought or sown again every year	Bought once
First-year look	Flower in their first season	Often small until the third year
Upkeep	Replant yearly, deadhead	Deadhead, divide every 3 to 5 years
Climate limit	Grown for one season in any zone	Must be hardy in your zone
Examples	Petunia, marigold, zinnia, impatiens	Daylily, hosta, peony, coneflower

Cost and Effort Over Several Years

On price, University of Vermont Extension puts it plainly: perennials tend to be more expensive than annuals, but they are an investment for the long term. An annual bed is a bill that repeats every spring. A perennial bed costs more in year one and little after that, provided the plants are hardy where you live.

The perennial pays back slowly. Washington State quotes the old gardener’s saying that the first year they sleep, the next year they creep, and the third year they leap. A bed planted entirely with young perennials can look sparse for two summers.

Perennials are not free of work either. Alabama Extension notes that most perennials need dividing every 3 to 5 years to maintain healthy growth and flowering. Division also produces new plants at no cost, and the steps are in our guide to dividing perennials.

How to Choose for Your Bed

Three questions decide it. How long will you keep this bed? Do you need color this summer or structure for years? And is the plant hardy in your zone?

Choose annuals for pots, hanging baskets, a rental, or any spot where you want color from spring to frost this year and may change the scheme next year. Choose perennials for a bed you expect to keep, and pick several with different bloom times so the 2 to 8 week windows follow one another. The low-maintenance perennials guide lists reliable candidates.

For anything tagged with a zone range warmer than yours, such as zones 9 to 11 in a zone 4 garden, budget for it as an annual.

Building a Bed That Uses Both

Most flower beds work best with both types. Use perennials as the permanent framework and set annuals in the gaps and along the front edge. While the perennials are still in their sleep and creep years, the annuals hide the bare soil for the first two summers. Once the perennials leap in year three, the gaps shrink and so does the yearly annual order.

The mix also covers the bloom gaps. A peony that flowers for less than a week and a yarrow that runs six weeks or more still leave months of the season open, and a few zinnias or marigolds between them carry color through to autumn frost.