9 Flowers to Grow in a Cold Frame in February
A protective cold frame lets us start flowers early for a head start on growth. Many gardeners can grow cold-hardy blooms in late winter. Garden expert Katherine Rowe looks at flowers to grow in a cold frame this month to usher in a blooming spring.
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Cold frames are simple structures that lengthen the growing season by letting us grow flowers and vegetables in cool conditions, even in late winter. They give a headstart on cool-season crops while harnessing the sun’s warmth for insulation. The basic structures range from an unheated greenhouse to a sunken wooden box or covering atop a raised bed.
When it comes to flowers to grow in a cold frame in February, start with those that thrive in the cool season. These include cold-hardy annuals and perennials that enjoy cool temperatures to germinate. With protection from the frame, they develop for transplanting as we move from late winter to early spring.
Hardy annuals are frost-tolerant and make the transition from cold frame to garden location in spring’s fluctuating conditions. They lengthen the bloom display for weeks with an early start before warm season flowers emerge later in the season. Pollinators appreciate the early nectar and pollen sources. Save any tender, heat-loving blooms for growing in the cold frame in the spring.
The Cold Frame Advantage
Cold frames use passive energy from the sun to warm ambient air in the enclosure. As sunlight passes through the glass, plastic, or fabric covering, it’s trapped in the frame to warm the surroundings.
Similar to a greenhouse, a cold frame extends the growing season by giving a headstart on growth. They let us start cool season annuals earlier in the season, even in winter, and warm season selections in the spring. We can also use them to overwinter frost-sensitive specimens and harden off seedlings as they move from indoors to out.
Situate the cold frame where it can harness the sun’s rays—a south-facing situation allows the most sun and heat. For added insulation, dig the frame into the ground to benefit from the protective soil mass or nestle it next to a wall. Surround it with straw bales for easy insulation. If your frame allows it, heat mats and other heaters add warmth for germination.
Temperature and Timing
Growing flowers in a cold frame depends on your climate and frost date. A cold frame captures heat during the day for warmth. At night, this cools to only a 5-10° difference between outdoor and in-frame temperatures. Depending on the climate, this makes for chilly nights.
Most cool-season flowers are ready to plant four to six weeks before the final frost date in the spring. Cold frames give us a couple of weeks’ head start—grow flowers in a cold frame as early as six to eight weeks before transplanting into beds or containers. Your climate, temperature, and variety impact development and transplant timing.
Starflower
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botanical name Scabiosa stellata |
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sun requirements Full sun to partial shade |
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height 18-24” |
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hardiness zones 3-9 |
Starflowers are pretty in bloom and beguiling in seed. Wiry stems hold light periwinkle blue flowers that open to translucent, papery, cupped seedheads with dark, starry, five-pointed centers. The creamy cups form small spheres one and a half inches across.
Starflower brings delicate interest and detail to fresh and dried florals. The annuals flower prolifically from mid-summer through frost for enjoying at both bloom and seed stages. Long, thin stems are multi-branched with silvery green foliage.
The blooms attract pollinators, and the plants are deer-resistant. For another pincushion flower to grow in a cold frame, look to Sixalix atropurpurea ‘Black Knight.’ This scabiosa has dramatic scarlet-black blooms with a sweet scent and durable nature, and it is drought-tolerant once established.
Calendula ‘Zeolights’
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botanical name Calendula officinalis ‘Zeolights’ |
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sun requirements Full sun |
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height 12-24” |
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hardiness zones 9-11 |
Calendula is a long-blooming, frost-tolerant annual that brightens both the ornamental and edible arrangements with edible leaves and flowers. It produces ray flowers in rich yellow, orange, pink, ivory, and bicolor varieties. In cool climates, the flowers emerge from spring to frost. In hotter growing zones, it grows best in the cool temperatures of fall and spring and even over the winter for seasonal color.
‘Zeolights’ boasts color-shifting petals that begin bronze-orange and transition to soft pink as they age. With fully petaled, double blooms, this calendula shines. Drought-tolerant and pollinator-attracting, ‘Zeolights’ is a showy and reliable cool-season performer.
Calendula is easy to grow and develops quickly from seed, blooming in as little as 30 days after germination. After growing the flowers in a cold frame in February, transplant seedlings as soon as the soil is workable. Provide mulch for the fast-growing seedlings as protective insulation. Calendula may self-sow for another round of future blooms.
Snapdragon ‘Potomac Appleblossom’
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botanical name Antirrhinum majus ‘Potomac Appleblossom’ |
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sun requirements Full sun |
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height 30-36” |
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hardiness zones 7-10 |
Snapdragons are classic, hardy annuals with bloom spikes in tones from pastel to bold that complement any display. In mild winter climates, they bloom all winter long. In colder climates, snaps flower in spring, summer, and fall.
Depending on the variety, snapdragons take 60 to 80 days or longer to mature from seed. For the best germination and earliest flowering, start them eight to ten weeks before the first frost date. February is ideal for many of us to sow seeds indoors or with a protected cold frame situation. Snapdragons are hardy to 25°F (-4°C) and perhaps lower with mulch and protection. Remove spent blooms to keep them from going to seed to promote continued blooming.
‘Potomac Appleblossom’ blooms are fresh and springy in rose and white. Petals are white with a pink blush, and flower centers are golden yellow surrounded by deep rose. ‘Potomac’ has extended blooming and tolerates longer daylight periods and warmer temperatures. They’re a favorite among growers for long-lasting flowers (deadhead after the first flush for more blooms).
Viola ‘King Henry’
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botanical name Viola cornuta ‘King Henry’ |
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sun requirements Full sun to partial shade |
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height 4-8” |
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hardiness zones 6-9 |
Violas survive winter in mild climates and withstand seasonal transitions in colder climates. Like snapdragons, they flower reliability in chilly weather and tolerate frost.
‘King Henry’ showcases velvety purple blooms that sparkle in the early spring display. Flowers have bright violet wings against a throat of dark purple, white, and yellow with deep whiskers. Each little detailed violet resembles a miniature orchid. Tuck them liberally into the front of the border or in containers.
Delicate in appearance, the durable annuals tolerate temperatures in the 20s°F (-7°C) and sometimes lower. Leaves may turn gray during cold snaps but recover as temperatures warm.
Sweet Pea ‘High Scent’
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botanical name Lathyrus odoratus ‘High Scent’ |
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sun requirements Full sun to partial shade |
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height 6-8’ vines |
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hardiness zones 7-10 |
Ornamental sweet peas charm with fragrant, colorful flowers on twining vines. A pollinator-attractor and ornamental bloom, they also make a lovely cut flower added to bouquets.
‘High Scent’ has long stems of billowy, creamy white blooms with ruffled lavender edges. One of the most fragrant varieties, a single stem fills the room with sweetness.
Sweet peas are frost-tolerant and grow quickly from seed, with ideal growing temperatures between 55 and 65°F (13-18°C). Their vines cling and climb and do best with a support structure like a tripod or trellis. Use them as a container focal point for vertical interest.
Stock ‘Apricot’
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botanical name Matthiola incana ‘Apricot’ |
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sun requirements Full sun to partial shade |
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height 18-30” |
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hardiness zones 7-10 |
Stock is an old-fashioned annual or tender perennial with aromatic flowers on stiff stems. With single or double white, pink, red, purple, and copper flowers, it makes a lovely cut flower with a sweet, spicy perfume.
‘Apricot’ is even sweeter with soft tones of peach, pink, and cream on tall, full stems. The pretty neutral complements deep blues and purples. Some from seed will be double-flowered and some single, so sow plenty for a usable mix.
Stock is hardy to about 25°F (-4°C) and prefers cool, moderate conditions. It doesn’t survive hot summers or frigid winters. It grows easily from seed, usually germinating in seven to ten days. Grow them in a cold frame before transplanting while the weather is still cool. In warm climates, treat them as early spring or fall annuals, with sowing earlier in the winter.
Bachelor Button ‘Polka Dot Mix’
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botanical name Centaurea cyanus ‘Polka Dot Mix’ |
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sun requirements Full sun to partial shade |
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height 16-24” |
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hardiness zones 2-11 |
Annual cornflower has rich blue flowers that flush in late spring and early summer with a light repeat bloom in fall. The ruffly petals on upright stems attract butterflies, followed by birds who enjoy the seeds.
‘Polka Dot Mix’ is a blend of the best in blue, violet, pink, red, and white blooms on compact stems. The complementary shades bring a wave of color to the border or container arrangement and are edible as a pretty garnish. They tolerate light frost, bloom prolifically, and are drought-tolerant once established.
In their prime growing conditions, especially in northern climates, cornflower reseeds and can become invasive. Deadhead blooms to prevent reseeding. Asters, fleabane, and penstemon offer native alternatives to the carefree cornflower.
Flax ‘Blue and Breezy’
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botanical name Linum grandiflorum |
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sun requirements Full sun to partial shade |
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height 1-3’ |
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hardiness zones 5-8 |
Flax is valuable for its seeds, oils, fibers, and flowers. Carefree and low-maintenance, they tolerate hot and cool weather and make good transitional-season growers.
Blue flax (L. lewesii) is a Western native perennial named for explorer Meriwether Lewis who collected plants on his westward journey. They thrive in dry, disturbed sites and work well on slopes and as erosion control. Blue flowers open in the morning and close or drop in the bright afternoon sun. Native bees and honeybees pollinate each five-petaled blossom. L. grandiflorum ‘Blue and Breezy’ is an easy seeder with showy sky-blue flowers followed by edible seeds.
Flax has roots sensitive to transplant disturbance. Transplant them as soon as the soil is workable (and before they develop extensive roots). Direct sowing works well. Sow by scattering seeds on moist soil and gently tamping for contact. The seeds need good light exposure to germinate.
Rocky Mountain Blue Penstemon
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botanical name Penstemon strictus |
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sun requirements Full sun to partial shade |
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height 2-3’ |
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hardiness zones 4-9 |
Penstemon boasts tall spikes loaded with bell flowers. Many species of beardtongue are native to the U.S. and are widely cultivated because of their brilliant blooms, dark green foliage, and pollinator benefits.
Rocky Mountain blue is a long-lived, reliable heirloom perennial with striking violet-blue bloom spikes in early summer. The adaptable grower tolerates varying soil conditions.
Penstemon prefers dry, light, well-drained soils. Seeds benefit from cold stratification, and direct sowing or cold frame conditions allow exposure to weeks of cold temperatures and moisture.
