Chocolate Cosmos (Cosmos atrosanguineus)
Description
Chocolate Cosmos are tender perennial tuberous plants (grown as annuals in cooler climates) prized for their dark, chocolate-scented blooms. They bloom mid-summer through fall, attracting pollinators and making a striking addition to any garden. Their unique color contrasts beautifully with bright summer flowers and adds depth to bouquets.
Details:
Plant type: tender perennial (grown as annual in zones 7 and below)
Height: 18–24”
Site: full sun to partial shade
Days to maturity: 90–100 days from tuber planting
Plant spacing: 12–15”
Pinch: optional, to encourage branching
Kids, Pets, and Deer: non-toxic, deer resistant
Indoor & Pots: grows well in containers; bring indoors in cold climates
How to Grow:
From Tubers (recommended): Plant dormant tubers in spring after the last frost. Soak tubers in water for a few hours before planting to encourage sprouting. Plant 2–3” deep in fertile, well-drained soil. Water gently and keep soil consistently moist until growth begins.
Direct seed: Chocolate Cosmos can be grown from seed, though germination is slow and may take several weeks. Sow indoors 8–10 weeks before the last frost, pressing seeds lightly into the soil surface without covering them deeply. Keep soil warm (around 70–75°F) and moist until seedlings emerge.
Succession planting is not necessary; focus on healthy tuber growth and regular deadheading to encourage continuous blooms.
Germination: Seeds: 2–4 weeks at 70–75°F (21–24°C)
Tubers: sprout in 7–14 days after planting in warm soil
Where to Plant: Full sun is best for strong, prolific blooms. Chocolate Cosmos prefer fertile, well-drained soil enriched with compost. In hotter climates, provide afternoon shade to protect foliage and flowers.
Harvesting / Vase Life: Cut flowers when blooms are fully open. Chocolate Cosmos have a moderate vase life of 5–7 days. For best results, cut stems in the morning and place immediately in fresh water. Regular deadheading will encourage additional blooms and prolong flowering.