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Key Features
Attracts PollinatorsAttracts ButterfliesFragrant (moderate)Container Friendly
Native to North America
Maintenancemoderate
Overview
A tender tuberous perennial reaching 18–24 inches (45–60 cm) tall and 12–18 inches (30–45 cm) wide, grown as an annual in most of North America. Stems slender, branched, green to reddish, arising from fleshy tuberous roots. Leaves pinnately divided, 3–5 inches (7.5–13 cm) long, with narrow lance-shaped segments, medium green. Flower heads solitary on long stalks, 1–1.5 inches (2.5–4 cm) across, with 8 velvety dark maroon-red to near-black ray florets surrounding a small dark maroon disc; individual florets are silky-textured. A distinctive warm chocolate scent, most pronounced during warm afternoons, arises from the flowers. Does not set viable seed in most garden conditions; propagated by division of tubers or cuttings. In zones 9–11, persists year-round as a tuberous perennial.
Native Range
Cosmos atrosanguineus is native to Mexico, where it is considered extinct or nearly so in the wild. The species survives primarily through cultivation, having been maintained in gardens since its introduction to European horticulture in the late 19th century. Wild populations are documented from oak and pine-oak woodland margins in central and western Mexico.Suggested Uses
Planted in mixed borders and cutting gardens at 12–15 inch (30–38 cm) spacing where the chocolate-scented flowers can be appreciated at close range. Used in containers of 3–5 gallons (11–19 L); the dark flower color provides strong contrast against lighter companions. Cut flower stems last 5–7 days in water; cut when 1–2 florets on a stem are open.How to Identify
Appearance
Size & Dimensions
Height1'6" - 2'
Width/Spread1' - 1'6"
Reaches mature size in approximately 1 years
Bloom Information
Blooms from June through first frost in annual culture, typically July through October in zones 5–8. Peak bloom July through September. In zones 9–11, may bloom nearly year-round with reduced output December through February. Individual flower heads last 5–7 days; plants produce new buds continuously at branch tips. Chocolate scent strongest on warm afternoons above 70°F (21°C).Detailed Descriptions
Flower Description
Very dark maroon-red to near-black; velvety texturedFoliage Description
Medium green, pinnately divided with narrow lance-shaped segmentsGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
In zones 7 and colder, start tubers indoors 4–6 weeks before last frost or purchase transplants; plant outdoors after last frost when soil has warmed to at least 60°F (16°C). In zones 8–9, tubers may overwinter in the ground with a protective mulch layer of 3–4 inches (7.5–10 cm). Space plants 12–15 inches (30–38 cm) apart in full sun. Water when the top 2 inches (5 cm) of soil are dry; overwatering causes tuberous root rot — well-drained soil is essential. Apply balanced fertilizer (10-10-10) monthly during the growing season. Lift tubers after the first frost in zones 7 and colder; store in barely damp peat or vermiculite at 40–50°F (4–10°C) over winter. No serious pest or disease problems; aphids occasionally cluster on growing tips.Pruning
Deadhead spent flower heads by cutting back to the next lateral bud to keep the plant producing new buds and extend the bloom season by 2–3 weeks. Cut back by one-third in midsummer if plants become leggy. After the first frost in zones 7 and colder, cut stems back to 2–3 inches (5–7.5 cm) above the tuber before lifting and storing for winter.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summerfall
Maintenance Level
moderateContainer Growing
✓ Suitable for container growing
Minimum container size: 3 gallons