Cold Climate Annuals: Learn About Growing Annuals In Zone 3

Cold Climate Annuals: Learn About Growing Annuals In Zone 3

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By: Mary H. Dyer, Credentialed Garden Writer

Zone 3 annual flowers are single season plants that don’t have to survive the climate’s sub-zero winter temperatures, but cold hardy annuals face a relatively short spring and summer growing season. Keep in mind that most annuals will grow in zone 3, but some are able to establish quicker and produce blooms sooner.

Annual Plants for Zone 3

Luckily for gardeners, even though summers are short, cold climate annuals manage to put on a real show for several weeks. Most cold hardy annuals can tolerate a light frost, but not a hard freeze. Here is a list of beautiful cold climate annuals, along with a few tips for growing annuals in zone 3.

Zone 3 Annual Flowers for Sunlight

  • Petunia
  • African daisy
  • Godetia and Clarkia
  • Snapdragon
  • Bachelor’s button
  • California poppy
  • Forget-me-not
  • Dianthus
  • Phlox
  • Sunflower
  • Flowering stock
  • Sweet alyssum
  • Pansy
  • Nemesia

Annual Plants for Zone 3 Shade

  • Begonia (light to medium shade)
  • Torenia/wishbone flower (light shade)
  • Balsam (light to medium shade)
  • Coleus (light shade)
  • Impatiens (light shade)
  • Browallia (light shade)

Growing Annuals in Zone 3

Many zone 3 gardeners like to take advantage of self-sowing annuals, which drop seeds at the end of the blooming season, and then germinate the following spring. Examples of self-sowing annuals include poppy, calendula and sweet pea.

Some annuals can be grown by planting seeds directly in the garden. Examples include California poppy, Bachelor’s button, black-eyed Susan, sunflower and forget-me-not.

Slow-blooming annuals like zinnias, dianthus and cosmos may not be worth planting by seed in zone 3; however, starting the seeds indoors gives them an earlier start.

Pansies and violas can be planted early in spring, as they tolerate temperatures a few degrees below freezing. They generally continue to bloom until arrival of hard freezes.

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Annual Plants vs. Perennials and How to Use Them

Wi Buy Wirach Thn Phanth / Getty Images

What makes annual plants "annual" and perennial plants "perennial?" Well, the answer lies in their respective life cycles. "Life cycle" means the amount of time it takes a plant to grow from seed and end up, finally, bearing seeds of its own.  

Botanically speaking, annual plants complete their life cycle within one growing season (typically, from spring to fall):

  • You place the seeds from last year's flowers in the ground in spring.
  • New annual plants sprout from the seeds.
  • With proper care, during the summer, these produce flowers.
  • Toward the end of the growing season (late summer or early fall), annual flowers yield seeds, signaling to the plants that their life cycle is complete. Having achieved their reproductive mission, they will die when the first hard frosts of autumn arrive.
  • But in many cases, if you practice deadheading on them during the summer to foster reblooming, you can get a lot of value out of them as fall flowers in the early part of autumn. Deadheading, you might say, tricks a plant into blooming a little longer than its natural life cycle would call for.

Celosia (Celosia)

If you notice a similarity between the flowers of celosia and amaranth, it's because they are both from the same family. The name celosia comes from the Greek word for "burning" because the flower heads of Celosia argentea look like brilliant flames.

Another variety is Celosia cristata, also called crested celosia or cockscomb, which has rippled flower heads that look like a rooster's comb. Furthermore, Celosia spicata has subtle flowers that are likened to wheat spikes. Celosia flowers remain attractive for weeks, and most varieties also make great cut and dried flowers.

  • Color Varieties: Red, pink, purple, orange, yellow, white
  • Sun Exposure: Full sun
  • Soil Needs: Rich, moderate moisture, well-draining

Lisa's 5 Cool Flowers for Getting Started

If people want to try planting hardy annual flowers, what are your sure-fire varieties to start with?

I can suggest 4 that are included in Cool Flowers, plus a new, fifth one.

5 Cool Flowers to Plant in Late Summer/Fall or Very Early Spring

Snapdragons (Antirrhinum majus) should be started indoors and then transplanted. They are so cold-hardy. I have documentation up to Zone 4, so that's most of the country. I grow several varieties of snaps, with the 'Chantilly' and 'Madame Butterfly' Series topping the list.

Rudbeckia 'Indian Summer' (Rudbeckia hirta) should also be started indoors and then transplanted. They don't care how cold, how wet, how icy it is. When we plant 'Indian Summer' in the fall we sometimes have blooms by Mother's Day.

For direct sowing in the garden, I suggest bupleurum (Bupleurum griffithii) and larkspur (Delphinium consolida). And P.S. — I could grow two acres of bupleurum and still not have enough for my florists.

What is your newest addition to suggest?

Stock (Matthiola incana), the seeds of which should be started indoors before transplanting outdoors. I wasn't 100% sure about stock when Cool Flowers was published, but I have learned since that it does survive my Zone 7 garden when planted in the fall. In fact, it tried too hard to bloom at Christmas, so now we only plant in very early spring. We grow a ton of stock and plant it 8 weeks before our last expected spring frost. It's well below freezing at night, cold during the day, and stock performs beautifully.

By the way, it is the strongest germinating plant I have ever grown — super easy to start from seed. I love Johnny's 'Quartet' Series — and we can harvest by Mother's Day with this technique.

Thanks, Lisa! You've certainly given me confidence to try planting "cool flowers" this fall in my Zone 8 cutting garden.

More people should try this. Our grandmothers practiced this — they may not have done a lot of record-keeping, so we don't have precision Zone documentation for every variety, and zones and microclimates vary over the years. But this isn't a new thing. When researching for Cool Flowers I found a book that included planting hardy annuals published in 1951, The Better Homes & Gardens garden book!

When I teach flower farmers this technique, I offer this encouragement: "These plants are not afraid of the cold — so you needn't be, either!"