Don’t Winter Sow These 11 Popular Flower Seeds: What to Do Instead
Winter sowing is a useful and easy way to start seeds and gives seedlings a strong start in natural conditions. However, this method is not as great for some species. Garden expert Katherine Rowe explores popular flowers and their seed-starting methods for quick development.

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Winter sowing is a simple and rewarding way to get a jumpstart on spring growing, whether direct sowing (even on snow) or insulating seeds in homemade mini greenhouses. The premise of winter sowing is that seeds hold over the winter until conditions are conducive for their germination. The technique works with nature and seasonality to promote sprouting when temperatures are right.
Winter sowing has big advantages: it gives seedlings a headstart toward flowering and fruiting, provides cold stratification for those that need it, and requires no hardening off for the tender growth to acclimate to outdoor conditions. As early as December or January, you can winter sow many selections, especially those that are hardy or need cold temperatures before germinating.
While you can winter sow just about anything with the insulated container method, it works especially well for native perennials, cold-tolerant herbs and vegetables, and cool-season annuals. With direct sowing in winter, some favorite flowers won’t show high germination rates.
Some are heat-loving and sprout later in the season, don’t require a chill period, or grow quickly sown post-frost. Others have a long germination time, best started indoors for timely warm-season flowering. Here, we’ll explore which flower seeds you should not winter sow.
Zinnia

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botanical name Zinnia elegans |
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sun requirements Full sun |
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height 1-3’ |
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hardiness zones 2-11 |
While you can sow zinnias outdoors in protective containers or start them indoors in winter, they don’t benefit from being planted early. It’s simplest to direct sow them in warming temperatures one to two weeks after the final frost. They grow quickly from seed and flower in the summer heat.
Zinnias bring vibrant double-disc flowers that are beacons for pollinators. Seed them in a mass for a nonstop display; the heat-loving annuals bloom from early summer through frost. The cut-and-come-again bloomers benefit from deadheading or use them in fresh arrangements, and the reward is more flowers.
Zinnias need good air circulation, well-drained soil, and sun to prevent pests and fungal diseases, especially in humid climates. In areas like the South with high heat and humidity, try disease-resistant varieties like the tall ‘Queen’ series and ‘Profusion,’ a dwarf zinnia loaded with successional blooms.
Sunflowers

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botanical name Helianthus annuus |
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sun requirements Full sun |
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height 2-10’ |
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hardiness zones 2-11 |
Like zinnia, sunflowers germinate in warm conditions. Don’t use resources on winter sowing sunflowers, but sow them outside one to two weeks after the last frost. Plant them in groups for impact, and seed two to three successional plantings so that when one group fades, another takes its place. You can have the bright, cheery faces all summer and into autumn, followed by those prolific seedheads – a rich food source for songbirds and small mammals.
Sunflowers germinate quickly. Experiment with soaking seeds to soften the seed coat to hasten the process. Opt for dwarf selections for a faster display. ‘Teddy Bear’ has fuzzy yellow blooms on multi-branched stems. The small variety reaches only two to three feet tall and is excellent in containers and small spaces. The three to five-inch flowers are double and fine-petaled for extra fluff and color.
Sunflowers are sensitive to root disturbance at transplanting (another reason not to winter sow but direct sow post-frost). If you opt to start them indoors, aim for two to four weeks before the final frost. Use biodegradable pots that go right in the ground with the seedling to prevent root disruption.
Celosia

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botanical name Celosia spp. |
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sun requirements Full sun |
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height 6-36” |
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hardiness zones 10-11 |
Celosia stands apart with plumes of brilliant color and texture in fuzzy red, magenta, yellow, and orange. Depending on the group, flowers are plumes, spikes, or ruffly fan shapes. Celosia makes an excellent cut or dried specimen, sometimes fading to vintage tones.
For a soft look, Celosia ‘Flamingo’ brings rosy pink and silvery sheaths. As they age, the light silver becomes more prominent. Sow these indoors six to eight weeks before conditions warm for earlier flowering. It takes two to three weeks for sprouting. Outdoors, they appreciate soils above 60°F (16°C).
Celosia grows readily from seed and reseeds in the landscape. Deadhead spent blooms to prevent unwanted reseeding and pluck any volunteers.
Scarlet Flax

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botanical name Linum grandiflorum ‘Scarlet’ |
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sun requirements Full sun to partial shade |
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height 1-2’ |
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hardiness zones 2-11 |
Scarlet flax is an heirloom annual with a profusion of red flowers that attract pollinators. This ornamental flax is an easy one to sow outside; don’t winter sow flax, but scatter seeds one to two weeks before the final frost.
Direct sow ‘Scarlet’ onto moist soil and tamp gently for contact. The seeds require light exposure to germinate, so there’s no need to cover them with soil. Sow them every two to four weeks from spring through fall for ongoing color. In mild climates, sow them in fall to enjoy as a winter annual.
The easy-care, low-maintenance flowers tolerate variable conditions, including heat, humidity, and cool weather. Without deadheading, they self-seed for recurrent color. For a perennial flax, ‘Blue and Breezy’ produces edible seeds from sky-blue flowers.
Marigolds

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botanical name Tagetes spp. |
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sun requirements Full sun |
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height 6-48” |
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hardiness zones 2-11 |
Marigolds make a bright addition with blooms until frost. From summer to the harvest season, they embellish the annual border and vegetable garden as valuable companions. Their ruffly pompons delight in bright yellow, gold, scarlet, creamy white, and tangerine.
Marigold seeds do best in warm weather, and cool temperatures can delay germination, which is why this flower is best left out of your winter sowing. They are tough, sometimes reseeding in place, and fine to winter sow late in the season, but sowing indoors early fosters faster flowering.
Start them about four to weeks before anticipated transplanting outdoors. They do well in air temperatures above 55°F (13°C) and soil temperatures between 70-80°F (21-27°C). A heat mat indoors benefits germination if temperatures are on the cool side.
Between French, Signet, African, and Mexican species, there’s a marigold for nearly every garden, at least until heavy frost. Signets (Tagetes tenuifolia) are the most petite and tastiest; French, too, make a pretty garnish in salads and on serving platters.
Amaranth

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botanical name Amaranthus spp. |
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sun requirements Full sun |
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height 2-6’ |
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hardiness zones 2-11 |
Amaranth offers unique blooms, either in draping ropes or upright plumes, in burgundy, gold, coral, and magenta. They add spectacular color and texture to fresh and dried florals. Flowers develop into high-protein seeds, and birds forage on those left to dry on the stem.
‘Coral Fountain’ and ‘Emerald Tassels’ feature ropes of trailing blooms. ‘Red Spike’ arches gracefully in deep crimson. I love ‘Hot Biscuits’ for its name, but mainly for its honey plumes as a warm, mellow, neutral.
Amaranth flowers from late summer through frost. The heirloom grain is best direct sown in warm soils between 65-75°F (18-24°C).
Begonia

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botanical name Begonia spp. |
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sun requirements Partial to full shade |
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height 1-1.5’ |
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hardiness zones 10-11 |
Because of their lengthy days to maturity, don’t winter sow begonia seeds but give them a boost with indoor-starting for earlier flowers. They germinate in about 2 weeks and can take around 110 days to mature for blooming, depending on the variety. Get them going inside as soon as possible to move out in warm conditions. For tuberous begonias, this can be 14 to 16 weeks before transplanting. The seeds need warm soils near 75°F (24°C) for the most successful germination rates.
Begonias are durable summer annuals that bloom despite hot, dry, and humid conditions. The old-fashioned workhorses brighten shady beds, hanging baskets, and containers with delicate blooms hanging from arching stems with thick, textural foliage.
Begonias are old-fashioned garden favorites due to their hardy performance in summer conditions and continual blooms from spring until frost. They’ll love spending summer outdoors and overwinter indoors for year-round interest. Their flowers are edible with a hint of citrus flavor.
Cosmos

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botanical name Cosmos bipinnatus |
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sun requirements Full sun |
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height 24-48” |
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hardiness zones 2-11 |
Sun-loving cosmos produce colorful ray flowers throughout the warm season on tall, airy stems. This summer annual is native to the Americas and lends a wildflower look to the display. They grow quickly from seed in optimal conditions. While they germinate well in winter-sown containers, they don’t need cold stratification and grow quickly in the landscape. Scatter them in a mass for an easy, large show of color that draws pollinators. Direct sow one to two weeks post-frost when soils are at least 60°F (16°C).
‘Rubenza’ is a bold Fleuroselect winner in deep, dusky wine and rose. ‘Apricotta’ is another award-winning variety with multiple peachy pink shades. Petals have lavender-pink interiors that fade to dusky apricot and surround bright yellow centers.
Cosmos are easy-care and prefer hot, dry conditions with variable soils. Too much water, fertilizer, and organic richness hinders their vigor. When flowers finish blooming and go to seed, cut stems back to 12 to 18 inches tall for recurrent blooms.
Impatiens

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botanical name Impatiens walleriana |
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sun requirements Partial to full shade |
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height 6-24” |
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hardiness zones 10-11 |
Impatiens are among the most popular bedding annuals, with sweet blooms that cover mounding foliage from spring until frost, flourishing in warm temperatures and shady garden zones. Their single or double blooms in a rainbow of colors pop against their petite dark leaves.
Impatiens need warmth to sprout, develop, and flower. You can start them in winter sown containers with a late-season installment (April or May in cold climates), though flowers won’t appear until later in the season. Don’t winter sow impatiens seeds if you want early flowers. Start them indoors six to eight weeks before the anticipated last frost date for a jump on growth. Keep seed trays warm with temperature in the low 70s (~21°C).
There are two main types of ornamental impatiens: Impatiens walleriana, the classic shade-loving species, and Impatiens hawkeri, New Guinea impatiens. New Guinea impatiens feature larger flowers with elongated leaves, often deeper in color with a metallic sheen. They tolerate some sun better than the tuberous I. walleriana and are more resistant to mildew diseases. For a more sun-tolerant hybrid, look to the Sunpatiens® series.
Pentas

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botanical name Pentas lanceolata |
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sun requirements Full sun to partial shade |
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height 1-2’ |
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hardiness zones 10-11 |
Pentas burst with color and pollinator interest with their clusters of starry flowers in red, pink, lavender, and white. They bloom with the onset of summer temperatures and are showy until frost. The flowers keep hummingbirds busy as they visit each tiny bloom for its nectar – especially red varieties.
The ‘Butterfly’ series is a top performer and also low maintenance. ‘Butterfly’ pentas boast extended blooming and varietal colors, including pure white, lavender, rose, and violet. They’ll bloom nonstop til frost, with up to 20 bloom clusters per plant.
Pentas are tough annuals that withstand hot and humid summers and periods of drought. Start them indoors four to eight weeks before transplanting, and experiment with pre-soaking the seeds overnight. For later flowers, direct sow them after the final frost.
Tithonia

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botanical name Tithonia rotundifolia |
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sun requirements Full sun |
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height 1.5-6’ |
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hardiness zones 2-11 |
Tithonia, or Mexican sunflower, produces deep orange daisy-like flowers on tall stems. The ray petals fan around a bright yellow center and tower in the back of the border. The heat-loving annuals tolerate drought and less-than-ideal soils. They bloom nonstop in summer conditions until heavy frost and are a favorite of pollinators.
‘Torch’ is a tall variety with four- to six-foot-high multi-branching stems. Its fiery orange petals contrast with other late-season blooms, especially purple leaves and flowers. Pair it with ornamental grasses, millet, amaranth, mums, and aster for an autumnal display.
‘Fiesta del Sol’ is a dwarf variety and an All-America Selections award winner. It bears a profusion of blooms and attractive leaves on dense stems that reach only 18 inches tall. The flowers are rich and dark orange with continual reflowering.
Cool weather can delay development and flowering. Skip winter sowing and start these flower seeds indoors six to eight weeks before frost passes for a headstart, especially in cool climates. Mexican sunflowers grow easily from seed, scattered and lightly pressed into the soil for contact while maintaining light exposure. Direct sow after frost in warm soils for blooms in mid-summer that flourish late in the season.