Cosmos atrosanguineus (Chocolate Cosmos)

Velvety petals in the deepest wine — with a hint of chocolate in the air.

Cosmos atrosanguineus, known as Chocolate Cosmos, produces rich burgundy to near-black blooms with a soft, matte finish. In warm sunlight, the petals glow deep crimson, almost black at dusk — creating a moody, romantic presence in the garden.

True to its name, the flowers carry a subtle cocoa scent on warm days, making them as intriguing as they are beautiful.

Elegant and slightly mysterious, they pair beautifully with blush, cream, dusty rose, and silvery foliage.

Height: 18–24 inches
Bloom time: Mid-summer to early fall
Best for: Borders, containers, cut flowers
Fragrance: Light chocolate scent

A plant that feels almost gothic — refined, rare, unforgettable.

How to Grow Cosmos atrosanguineus

Warm soil and good drainage are key.

🌱 When to Plant

Plant tubers after all danger of frost has passed and soil has warmed (at least 10–12°C / 50–55°F).
In Alberta, this is typically late May.

You may start indoors 4–6 weeks earlier for earlier blooms.

🌿 Planting

• Plant 2–3 inches deep
• Space 12–18 inches apart
• Ensure the crown sits just below soil level

☀️ Light

• Full sun to light shade
• Best flowering occurs in full sun

🌱 Soil

• Well-draining soil is essential
• Avoid heavy, waterlogged areas
• Amend with compost if needed

Chocolate Cosmos dislikes wet feet.

💧 Watering

• Keep evenly moist during establishment
• Once established, moderately drought tolerant
• Avoid overwatering

✂️ Maintenance

• Deadhead regularly to encourage continued blooming
• Pinch early growth lightly to encourage branching

🍂 Overwintering (Cold Climates)

Cosmos atrosanguineus is not fully hardy in colder regions.
In Alberta:
• Lift tubers after first light frost
• Allow to dry
• Store in a cool (5–10°C), dry location over winter
• Replant in spring

Alternatively, grow as a seasonal annual.

Why Grow Chocolate Cosmos?

• Unique near-black blooms
• Subtle chocolate fragrance
• Compact and elegant growth habit
• Perfect for moody, romantic plant palettes

It’s a plant that feels like twilight in bloom — dramatic yet refined.