How to grow Cornflower in Australia
Cornflower (Centaurea cyanus), also called bachelor's button, is a hardy annual with ruffled flowers of an intense blue, as well as pink, white and near-black forms. It is easy from seed, thrives in poor soil, makes a long-lasting cut flower, and is a magnet for bees and butterflies. The petals are edible too. Sow in autumn for the earliest, strongest spring display.
📖 Our full guide: How to Grow Cornflower in Australia
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| South East Queensland | March to June | |
| Northern Rivers NSW | March to June | |
| Sydney & Coastal NSW | March to June | |
| Melbourne & Victoria | March to June | |
| Adelaide & SA | March to June | |
| Perth & WA | March to June | |
| Tasmania | March and April, September and October | Sow Sep to Oct or Mar to Apr. Autumn sowings overwinter for early flowers. |
| Canberra & ACT | March and April, September and October | Sow Mar to Apr to overwinter for early flowers, or Sep to Oct. |
| North Queensland | April to June | Sow Apr to Jun for dry season flowers. |
| Darwin & Top End | May and June | Sow May to Jun for dry season flowers. April is still too humid. |
Where to plant
Sow cornflowers in full sun in free-draining soil of modest fertility. They prefer poorer soil; rich soil or fertiliser gives tall, floppy plants with fewer flowers. They are frost hardy and do best in the cool to mild months.
Cornflower has naturalised in parts of Australia, spread as a garden escape and as a contaminant of crop seed. Deadhead plants near bushland and farmland so they do not seed beyond the garden.
- Sydney, Melbourne, Adelaide, Perth, South East Queensland and the Northern Rivers: sow from March to June for flowers in late winter and spring.
- Hobart and Canberra: sow in March and April to overwinter for early flowers, or in September and October for summer flowers.
- North Queensland: sow from April to June for dry-season flowers. Darwin: sow in May and June, as April is still too humid.
Choosing a variety
- Blue Boy is a classic tall blue cornflower, good for picking.
- Black Ball has deep maroon, almost black flowers.
- Dwarf mixes stay compact for pots and borders.
How to plant
- Sow seed directly where it is to flower, about 5 mm deep, and cover lightly.
- Keep the soil just moist; seedlings appear in one to two weeks.
- Thin seedlings to about 15 to 25 cm apart when they have their first true leaves.
- Do not add fertiliser.
Watering and feeding
Water seedlings until they are established; after that cornflowers tolerate dry spells and need watering only in long dry periods. They need no feeding.
Pruning and care through the year
- Deadhead or pick flowers regularly to keep plants blooming for longer.
- Tall varieties may need light support, such as twiggy sticks or a few stakes and string, in windy, open sites.
- Let a few flowers set seed at the end of the season if you want them to self-sow, away from bushland.
Picking flowers
For a vase, cut stems when the flowers are a quarter to half open; they last well in arrangements and also dry well. For eating, pick fully open flowers and pull the petals from the centre.
Growing in pots
Dwarf cornflowers grow well in a pot at least 20 cm wide with ordinary potting mix. Keep the pot in full sun, water when the top of the mix is dry, and do not feed.
Using it
- The petals are edible, with a mild, slightly spicy, clove-like taste. Scatter them over salads, cakes and drinks for colour.
- Use only flowers from plants that have not been sprayed.
Companion planting
Cornflowers were once a common weed of cereal crops, and they still look and grow best in a sunny, meadow-style planting with other annual flowers.
Good companions
- Wildflowers Annual meadow flowers share the same sun, poor soil and sowing time.
- Grains Cornflowers traditionally grew among cereal crops in the same open, lean ground.
Pests and diseases
Cornflowers are easy, with few problems. Aphids in spring and powdery mildew late in the season are the main ones.
Pests to watch for
- Aphids Clusters of small insects on stems and buds in spring.
Diseases to watch for
- Powdery mildew White, powdery patches on leaves late in the season. Pull out tired plants.
Common questions
When should I plant cornflowers?
Autumn is best in most of Australia, from about March to June, for flowers in late winter and spring. In cooler areas such as Hobart and Canberra you can also sow in early spring. Pick your region at the top of the page for the months.
Are cornflowers edible?
Yes, the petals are edible, with a mild, clove-like taste. Use them fresh to colour salads, cakes and drinks, from unsprayed plants.
Do cornflowers come back every year?
They are annuals, but they often self-seed, so new plants may appear next season if you leave a few flowers to set seed.
Why are my cornflowers floppy?
Usually the soil is too rich or the plants were fed. Cornflowers grow sturdier in poorer soil. Tall types may still need light support in windy spots.
When should I pick cornflowers for the vase?
When the flowers are about a quarter to half open. They last well in water and dry well too.
Are cornflowers good for bees?
Yes. Cornflowers are a magnet for bees and butterflies, especially the single blue types.
Sources we checked: RHS: Centaurea cyanus; Johnny's Selected Seeds: Centaurea key growing information; The Seed Collection: Cornflower.