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Cool Flowers (Plant These 10 Hardy Annuals Now for Beautiful Spring Blooms)
March is just around the corner, and spring planting is surely on your mind (when is it not?)
You might be planning your summer garden already and organizing your seeds, so they’re ready to plant. But what if you didn’t have to wait until summer to enjoy beautiful, fragrant flowers?
As much as we love zinnias and sunflowers, those aren’t your only option for your flower garden. There are some seeds that—if you plant them right now—will give you blooms by Mother’s day!
Alyssum, bachelor’s buttons, calendula, cleome, delphinium, foxgloves, larkspur, lisianthus, pansies, and rudbeckia—these gorgeous flowers are all easy-to-grow, hardy annuals that thrive in the colder temperatures in spring and fall.
Keep reading to learn more about hardy annuals and why we’re obsessed with these cool flowers, as well as when to plant them for the earliest spring blooms.
All about hardy annuals
What are hardy annuals?
Annuals have a one-year life cycle—they sprout, grow to maturity, flower, and set seeds all within a year. Cold-sensitive plants are called tender annuals. They thrive in warmer temperatures and won’t do well if planted before the soil warms. On the other hand, hardy annuals are plants made to withstand cold temperatures, even overwintering in all but the most extreme winter climates.
Hardy annuals don’t just tolerate colder temperatures—the plants actually require it. The seeds of many hardy annuals must go through stratification or a period of cold temperature that mimics a natural winter for the seeds to germinate.
Many of our favorite cottage garden flowers are hardy annuals, like foxgloves and larkspur. These cool-season flowering annuals will typically bloom early and die back by summer, although some species will bloom a second time when cooler temperatures return in fall.
Are hardy annuals difficult to grow from seed?
Some hardy annuals have a reputation for being challenging to grow from seed, but there’s no need to be intimidated by hardy annuals! The most significant inconvenience of starting hardy annual seeds is the timing—which could be spring or fall, depending on where you live.
When should hardy annuals be planted?
Unlike heat-loving annuals, hardy annuals can be planted in spring or fall. There are advantages to both planting windows; which window you choose will depend on your hardiness zone and how ready you are to sow seeds.
Fall planting
According to flower farmer and author Lisa Mason Ziegler, the key to successfully growing hardy annuals is to sow hardy annual seeds in the fall. If you wait until spring to plant hardy annuals, it's already too late—the plants won’t have much time to bloom before their growing season is over. In her book Cool Flowers, Ziegler writes:
Flowers planted during cool weather will become well-established and grow a strong root system long before they are expected to begin performing. These healthy plants will stand on a sturdy foundation that will carry them through spring and into summer, taking on heat, disease, pests, and drought with little problem (xii, xiv).
In mild climates, hardy annuals do best when they are planted in the fall to allow the plants enough time for vegetative growth before the temperatures warm, and the plants are triggered to flower—fall planting results in bigger blooms and a longer bloom window.
According to Ziegler, the ideal time for fall planting is 6–8 weeks before your first frost date (29). This means that seeds started indoors must be sown 6–8 weeks before the fall planting date, or in midsummer.
Spring planting
Gardeners in cold climates will want to wait to sow hardy annuals until very early spring, and starting seeds indoors in late winter allows these growers to make up for the lost time in fall.
For spring planting, the timeline is nearly identical to fall planting: direct sow in the garden 6–8 weeks before the last fall frost date or start seeds indoors 6–8 weeks before the spring-planting date (Ziegler, 32, 33).
How to plant hardy annuals
Some hardy annuals prefer to be direct seeded outdoors, and others prefer to be started indoors.
Direct sow
To direct sow hardy annuals, first, prepare the garden beds for planting. Add any soil amendments if needed, and work a good bit of compost into the soil. Make a small furrow in the ground and sprinkle seeds in a line. You can use a seeder if you have one available. Once the row is seeded, gently rake a light layer of soil over the seeds and water the row.
For extra protection from the elements (and to help with germination), you can cover the garden bed with a polyester fabric like Reemay, a natural mulch such as straw, or even a plastic caterpillar tunnel.
Start indoors
To sow hardy annual seeds indoors, sow the seeds as usual. Cool-season flowers are some of the smallest seeds, so consider using some seed-sowing hacks outlined in this article. Winter rains usually keep outdoor-sown seedlings moist enough, but you’ll want to check indoor starts often to ensure the seedlings aren’t drying out or getting too hot in a greenhouse.
Hardening off
Even though hardy annuals are made for cold weather, you’ll still need to harden off indoor-grown seedlings before they can be planted outside. Start by putting the trays outside for a couple of hours each day, and increase the seedlings’ time outside until they spend the night unprotected.
Protecting hardy annuals from extreme cold
If you see a deep freeze in the forecast, you can take a few measures to protect your plants. First, water the plants thoroughly the evening before an anticipated freeze—the water will keep the plants from freezing.
You can also cover your plants with a bedsheet or a piece of Reemay. Line the bed with stakes or metal hoops to hold the fabric just above the plants without touching them—this insulating layer adds about 5 degrees of warmth.
Cool-season flowering annuals are tough. These plants are built to tolerate fluctuating and freezing temperatures—they don’t need to be babied.
If you’ve researched your hardiness zone and followed the recommended planting dates on the seed packets, nature will do the rest. With the proper care (and with a bit of intervention if the weather unexpectedly turns severe), your plants will be more than fine.
Why grow hardy annuals?
Because they bloom earlier than other annuals, hardy annuals help provide continuous color in a mixed garden. Fall-planted hardy annuals bloom in early spring, and even spring-planted hardy annuals begin blooming in the first part of summer. These early-blooming beauties draw pollinators to the garden before other plants have had time to mature, so your garden will be buzzing with activity long before your neighbors’.
10 hardy annuals that can take the cold
Our favorite cool-season flowers are tough enough to overwinter and beautiful enough to be in a bridal bouquet. These hardy annuals feature every color of the rainbow. They are widely adaptable to various climates, so you can enjoy these incredible flowers in your cutting garden or landscape wherever you are.
1. Alyssum
Sweet alyssum is aptly named for its sweet and soft fragrance, but you might be surprised to know that alyssum is actually a member of the mustard family. The edible stems and blooms have a slightly peppery flavor, but we prefer to grow alyssum as a groundcover for its compact, spreading growth habit. For a hardy annual, alyssum is pretty drought tolerant and heat resistant, and if pruned regularly, sweet alyssum will boast fragrant blooms from summer until fall.
One of the easiest cut flowers to grow, bachelor’s buttons are a favorite among pollinators and gardeners alike. The fluffy white, pink, and blue blooms are delightful in bouquets or the garden. Also called cornflower, bachelor’s buttons are hardier than they appear at first glance and readily self-seed themselves—so you’re sure to have volunteer plants whether you plan on it or not.
3. Calendula
Also called pot marigold—though there is no relation to true marigolds—calendula is a mainstay in the cutting garden. Calendula is an edible plant in the daisy family with medicinal properties to boot, so it’s a worthwhile addition to the garden. Calendula is a fast grower and striking bloomer—some varieties flower in as little as two months from planting.
4. Cleome
Although not the most common tenant in the average cutting garden, Cleome is an easy-to-grow and dazzling hardy annual. Also called spider flower, cleome is characterized by clusters of cream, rose, and lavender blooms with distinct thread-like stamens on each flower. Mature cleome plants reach between three and four feet tall, adding vertical interest to the landscape. Though not overly fragrant, cleome blooms are very popular with hummingbirds and butterflies.
5. Delphinium
The dainty, cool-colored spires could easily be mistaken for larkspur, but delphiniums are a different species. Technically short-lived perennials, many gardeners in colder regions grow delphiniums as hardy annuals. Growers in particularly warm climates will also have better success fall-sowing delphiniums and enjoying them in the spring, as the cool-season plants don’t thrive through hot, dry summers.
6. Foxglove
Foxgloves are among the most treasured blooms of all, and for good reason. The bell-shaped blooms feature gorgeous pastel hues and have a whimsical appearance, like something out of a fairytale. Technically a biennial, foxgloves are designed for fall planting and will bloom the following spring.
7. Larkspur
With its feathery foliage and jewel-toned blooms, larkspur is one of the more elegant early bloomers. Despite its regal persona, larkspur is easy to grow from seed—the deer-resistant, low-maintenance hardy annual frequently reseeds itself. Larkspur typically grows between three and four feet tall, making it an excellent choice for borders and ending walls and fences. Cut larkspur blooms when one-third of the florets have opened.
8. Lisianthus
Technically a tender perennial, lisianthus is commonly grown as a hardy annual. The North American native wildflower thrives in prairies and grasslands and is known for being difficult to grow from seed. But with the proper care, lisianthus will flourish—even through the summer heat—providing long-lasting, rose-like blooms from late spring through frost.
9. Pansy
Pansies are underrated as cut flowers but are renowned as a colorful groundcover. Although deer are known to browse pansies, a simple deer repellent or strategic planting can help prevent excessive damage to your garden. Pansies come in several delightful colors and patterns, and their adorable faces are edible—so try a few in your spring garden salad or a refreshing lemonade!
10. Rudbeckia
Some Black-Eyed Susan varieties are perennial, and some are annual, but either way, you can sow rudbeckia seeds in the fall. These hardy plants are known for their yellow daisy-shaped blooms and black centers, although many variations boast ruby or cream-colored blooms and even green “eyes.” Birds and beneficial insects love black-eyed susans, and cut flower farmers appreciate the productive blooms for bouquets.
Conclusion
Cool-season flowers are an underrated choice for gardeners looking for a low-maintenance addition to their garden or landscape. Fall-planting hardy annuals will result in early spring blooms lasting until midsummer and often beyond. With some preparation and care, you’ll be rewarded with beautiful blooms long before anything else begins flowering.
Hardy annuals are not that difficult to grow, so why not try them this season? You’ll be so proud when your tiny flower seeds grow into the most gorgeous spring garden.