Cosmos
Cosmos bipinnatus · Asteraceae
The gardener's calendar
Cosmos is in full bloom: enjoy it, watch watering in hot weather and let spent flowers feed pollinators before pruning.
ID card
- Family
- Asteraceae
- Type
- Annual herbaceous plant
- Flowering
- July to October
- Adult size
- 60 to 120 cm in height
- Foliage
- Deciduous, finely cut
- Hardiness
- Annual (frost-tender)
- Growth
- Fast
- Origin
- Mexico and Central America
Care
Bright Light Exposure
Cosmos demands a very sunny location (minimum 6 to 8 hours of direct sun daily) to flower generously. Full sun exposure guarantees abundant blooming and flowers with vibrant colors. In partial shade, the plant will remain greener but produce fewer flowers.
Moderate Watering
Water regularly during the growing and flowering periods, without letting the soil become waterlogged. Once established, cosmos tolerates drought well and needs little water: weekly watering is sufficient under normal conditions. Reduce watering during rainy periods.
Soil and Drainage
Cosmos adapts to most soils, even poor or rocky ones. Good drainage is essential to prevent root rot. Well-aerated, light soil is ideal; improve compacted soil with coarse compost or sand.
Light Fertilization
Cosmos doesn't require much fertilizer. A moderate application of balanced fertilizer once or twice during summer is more than enough. Excess nitrogen promotes foliage at the expense of flowers.
Pinching and Deadheading
Pinch young plants (remove the top 5 to 10 cm) when they reach 15 to 20 cm to encourage dense, compact branching. Throughout summer, remove spent flowers to extend blooming and encourage new flower buds.
Health and Pests
Cosmos is generally robust. In case of excessive moisture, fungi may appear (powdery mildew, rot). Ensure good air circulation and avoid wetting the foliage. Pests are rare; aphids may occasionally colonize young shoots.
Did you know?
Cosmos takes its name from the Greek 'kosmos' meaning 'order' or 'universe', referring to the harmony and regularity of its flowers. Native to Mexico, it became popular in Europe in the 19th century and became a staple of English cottage gardens, where it symbolizes wild and delicate elegance.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
Add this plant to my garden →Plants from the same family
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- Canadian goldenrodSolidago canadensis
- WormwoodArtemisia absinthium
Tips generated and checked by Viridia — adapt them to your local climate.