Cornflower

Cornflower

Centaurea cyanus

Sow outdoors 4 weeks before your last spring frost. Space plants 6 in (15 cm) apart.

Photo: Ruth Hartnup from Vancouver, Canada, CC BY 2.0 · source

When to plant

Timed from your frost dates, so it holds wherever you garden. Give yours and every step below becomes a date.

See the dates for your garden

Enter your average last spring frost and first fall frost. Every timing on this site turns into a calendar date. Not sure of yours? Your local extension service or a search for “last frost date” and your town will tell you; the app finds them from your location.

Last spring frost
First fall frost

Saved in this browser only. Nothing is sent anywhere.

Optimal Spring Direct Sow

From seedRecommended
  1. Sow outdoors4 weeks before your last spring frost
  2. First harvestabout 75 days after sowing

Optimal Fall Sow (Blooms Next Spring)

From seed
  1. Sow outdoorsaround your first fall frost
  2. First harvestabout 75 days after next spring's last frost

Optimal Indoor Start

From seed
  1. Start indoors6 weeks before your last spring frost
  2. Begin hardening off3 weeks before your last spring frost
  3. Plant out2 weeks before your last spring frost
  4. First harvestabout 70 days after sowing

Growing cornflower

Spacing in the row
6 in (15 cm)
Between rows
12 in (30 cm)
Planting depth
1/4 inch
Sun
Full Sun
Soil
Well-drained, average fertility, pH balanced
Germination
7-14 days at 60-70°F
Harvest season
Summer, Fall
Mature height
18-36 inches
Life cycle
Annual

Direct sow seeds shallowly; prefers cool soil for germination. Can be sown in spring or fall.

Watering. Keep consistently moist until established, then water moderately. Tolerant of dry conditions once mature.

Neighbours

The companion chart →

Grows well beside

Feeding

Seedlings
Not typically fed; relies on existing soil nutrients.
Growing
Optional light balanced granular fertilizer (e.g., 5-10-5) if soil is poor; apply once established.
Flowering and fruiting
Optional bloom-boosting liquid fertilizer (e.g., 2-10-10) every 4-6 weeks during peak bloom for continuous flowering.
How often
Rarely: a lean-soil flower; at most a light feed every 4 weeks.
Note
Generally a low-feeding plant; avoid excessive nitrogen which promotes foliage over flowers.

Your cornflower, planned to the day.

Canopy turns these timings into dates from your own frost data, places every plant at its spacing on your garden map, and tracks it all the way to harvest.

Add cornflower to your planting calendar →

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