Black Magic Cosmos is a remarkable resurrection of a nearly extinct Mexican heirloom that releases an intoxicating chocolate scent from deep burgundy-black flowers. This cultivar of Cosmos atrosanguineus was developed by renowned New Zealand flower breeder Dr. Keith Hammett, who transformed wild, scraggly plants into reliable garden performers that can be grown from seed rather than cuttings alone. Hardy in zones 9-11, these flowers bloom within 90-110 days and thrive in full sun with moderate water, reaching maturity at just 10 inches spacing. The chocolate aroma alone makes them unforgettable, but the dark, nearly black petals add drama and sophistication to any garden or bouquet.
Full Sun
Moderate
9-11
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Moderate
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The chocolate scent rising from these nearly black petals is genuinely intoxicating, a fragrance that seems more at home in a perfumery than a garden. Native to the pine and oak forests of Mexico's Trans Mexican Volcanic Belt, this species was once feared lost entirely, making every plant you grow a small act of botanical rescue. Dr. Keith Hammett's breeding work solved a century-old problem: gardeners had always loved chocolate cosmos but could only propagate them through cuttings, making them rare and fussy. Now you can grow them reliably from seed, filling your garden with flowers that smell like cocoa and look like deep burgundy velvet.
Black Magic Cosmos is grown primarily as an ornamental flower for gardens and cut arrangements. The deeply colored petals and chocolate fragrance make these flowers particularly valued for fresh bouquets, where the scent becomes even more apparent in enclosed spaces. Gardeners also grow them to attract pollinators and add sensory richness to borders and containers, leveraging both their visual drama and their distinctive aroma.
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Sow Black Magic Cosmos seeds indoors 6-8 weeks before your last frost date in trays or seed-starting mix. Keep the soil consistently moist but not waterlogged and maintain a germination temperature of 65-75°F. Seedlings should emerge within 7-14 days and can be potted up once they develop their first true leaves. Harden off seedlings gradually over a week before transplanting, exposing them to increasing amounts of outdoor light and air movement.
Transplant seedlings outdoors after the last frost date, when nighttime temperatures consistently reach 60°F or higher. Space plants 10 inches apart in full sun. Water gently at transplanting and keep soil moderately moist for the first few weeks as plants establish. These half-hardy plants will not tolerate frost, so wait until frost danger has completely passed before moving them into the garden.
Deadhead spent flowers regularly to encourage continuous blooming and prevent the plant from exhausting itself on seed production. Pinching back young plants when they reach 6 inches tall can promote bushier, more compact growth, particularly useful if you find your plants becoming leggy.
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“Chocolate cosmos originated in the pine and oak woodlands of Mexico's Trans Mexican Volcanic Belt, where it captivated gardeners for generations with its intoxicating chocolate aroma. By the early 21st century, the species was believed to be nearly extinct in much of its native range, with wild plants becoming increasingly difficult to source. For centuries, gardeners could only propagate these treasured flowers through cuttings, keeping them rare and primarily available through specialized nurseries. Dr. Keith Hammett, a renowned flower breeder from New Zealand, dedicated his work to transforming wild chocolate cosmos into a reliable garden plant that could be grown from seed. The result, Black Magic Cosmos, preserves the original's irresistible fragrance while producing plants that are more compact, uniform, and accessible to home gardeners everywhere, effectively rescuing this nearly extinct Mexican native from obscurity.”