Sea Shells Cosmos is an heirloom annual that transforms garden beds into coastal dreamscapes without requiring a trip to the shore. Unlike typical cosmos with flat petals, this variety sports intricate tubular and cone-shaped ray flowers that resemble delicate seashells, held aloft on tall 3 to 4 foot plants in shades of deep rose, shell pink, and snowy white. It reaches maturity in approximately 100 days (though some sources report 60 to 90 days), produces abundant three-inch blooms all summer until frost, and thrives in hardiness zones 2 through 11. Like most cosmos, it tolerates poor, dry soils and heat with ease, making it equally at home in cottage gardens or cutting gardens.
Full Sun
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2-11
48in H x 24in W
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Low
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The petals of Sea Shells Cosmos are coiled and tubular rather than the flat ray petals you'd expect, creating a sculptural, almost otherworldly form that catches light differently throughout the day. Each bloom resembles a tiny colorful shell held on a swaying stem, and when you plant a mass of them together, they create a reef-like effect of purples, pinks, and whites that sways in summer breezes. Butterflies and beneficial insects gravitate toward these flowers, making them as functional in a pollinator garden as they are beautiful as cut flowers or focal points in borders and wildflower beds.
Sea Shells Cosmos shine as cut flowers, their tall stems and unusual petal structure making them striking in vases and arrangements. They're excellent for cottage gardens, wildflower beds, and pollinator plantings where their abundance of blooms and ability to attract butterflies create both visual and ecological value. Mass plantings are particularly stunning, and because the plants sway gently in the breeze, they create movement and rhythm in the garden.
No timeline data available yet for this variety.
Start seeds indoors 4 to 6 weeks before your last spring frost. Sow seeds at 65 to 80 degrees Fahrenheit and keep soil consistently moist until germination. Transplant seedlings into individual pots when they develop true leaves.
Harden off seedlings gradually over 7 to 10 days before moving them outdoors after your last frost date. Transplant into garden beds or containers, spacing plants 12 inches apart. Ensure soil temperature has warmed to at least 70 to 75 degrees Fahrenheit for best establishment.
Direct sow seeds into garden beds after your last frost date when soil has warmed. Scatter seeds on soil surface and press gently to ensure contact; they need light to germinate. Keep soil consistently moist until seedlings establish, then thin to 12-inch spacing.
Cut flowers in early morning when stems are fully hydrated for longest vase life. Harvest when blooms have fully opened and petals have unfurled to their characteristic tubular shape. Cut stems at an angle just above a leaf node to encourage branching and additional flowers.
Sea Shells Cosmos responds well to deadheading, which encourages continuous flowering throughout the season. Pinching back young plants when they reach 6 to 8 inches tall promotes bushier growth and more blooms, though this delays flowering by a week or two.
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