How to grow cosmos in a raised bed

Cosmos are the easiest, most generous cottage flower — airy, daisy-like blooms on tall stems that flower for months and buzz with bees and hoverflies. Sow once and enjoy them all summer.

Quick facts

• Position: full sun
• Spacing: 30–40 cm apart
• Tub depth: our 23 cm+ depth
• Time to harvest: 10–12 weeks to flower

When should I plant cosmos?

Cosmos are frost-tender — sow directly from spring through summer. They often self-seed for the following year. Our free garden calendar shows the right months for your postcode.

• Subtropical (Brisbane & SEQ): August to January
• Temperate (Sydney, Melbourne, Adelaide, Perth): September to December
• Cool & mountain (Tasmania, Canberra, highlands): October to December
• Tropical (Cairns, Darwin): April to August
• Arid inland: March and August to November

How do I grow cosmos in a raised bed?

Sow seed straight into the mix in full sun — poor soil actually gives more flowers and fewer leaves. Deadhead or pick regularly and they'll bloom until the frosts.

How do I use it?

Cosmos are grown for cutting and for the pollinators rather than the plate — they're a superb, long-flowering nectar source that fills a garden with beneficial insects.

What pests attack cosmos?

Keep an eye out for aphids, though flowers are seldom much bothered. See our safe pest guide.

What are the common problems with cosmos?

The main one to watch is powdery mildew, usually in damp, crowded conditions. Good airflow prevents most.

Where should I plant it?

Dot them through and around the veggie beds to bring in bees and hoverflies; brilliant as cut flowers. See our companion planting guide.

More growing guides: calendula, cornflowers and sunflowers.

Plan your patch: our free garden calendar shows what to plant now where you live. Ready to grow? Browse our raised garden beds or build your own with the garden bed builder.

Image: Dominic Nelson, CC BY-SA 4.0, via Wikimedia Commons.