Cosmos: An Easy Annual for an Airy Flower Bed

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Cosmos is one of the easiest garden flowers: sow the seed in May and from midsummer to the frosts you will enjoy a cloud of light daisies above feathery foliage. It grows in almost any soil, draws butterflies and self-seeds. Here are the varieties, how to sow and a few secrets for plenty of flowers rather than just foliage.

Types and varieties

• Garden cosmos (Cosmos bipinnatus) — the main species, 60–150 cm: the 'Sensation' series (pink, white, crimson), double 'Double Click', cup-shaped 'Cupcakes', tubular-petalled 'Seashells' and dwarf 'Sonata'.
• Sulphur cosmos (C. sulphureus) — yellow, orange and red, heat-tolerant.
• Chocolate cosmos (C. atrosanguineus) — maroon flowers that smell of chocolate; lift the tuberous roots for winter like dahlias.

When and how to sow

• Outdoors: in May after the frosts, 2–3 seeds per station, 1 cm deep, 30–40 cm apart.
• Seedlings: in April for earlier flowers; they germinate in about a week.
• Autumn sowing: sow in November and cosmos comes up in spring.

Care: less is more

• Sun: at least 6 hours a day.
• Soil and feeding: cosmos flowers best on poor soil; fertiliser and compost give lush foliage and late flowers.
• Pinching: pinch out the tips of young plants at 30 cm for a bushier plant.
• Deadheading: extends flowering; leave a few heads to set seed.
• Support: tall varieties need staking in windy spots.

Cosmos in bouquets

Cosmos is a favourite for garden-style bouquets — light, airy and softly coloured. Cut early in the morning as the flowers begin to open; they last 5–7 days and buds keep opening. It pairs with cornflowers, tanacetum and grasses. More ideas in annuals for flower beds and wild flowers; the full A–Z is in types of flowers. Cosmos is considered safe for people and pets.

View full-size photoCosmos of various types and colors in a garden bed.

FAQ

Why is my cosmos growing but not flowering?

Usually too much fertiliser or very rich soil, or too much shade.

When should I sow cosmos outdoors?

In May after the frosts, or in November for spring germination.

Does cosmos self-seed?

Yes — leave a few spent flowers and new plants will appear next year.

Author: Maria Svitlovir

Graduated from Taras Shevchenko National University of Kyiv, Institute of Biology and Medicine (2001). BSc in Biology, MSc in Horticulture. Writes about plants, works at a garden centre selecting and repotting plants, and contributes to plant reference guides.

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