GardenAnnual Flower · 16 varieties
Cornflower
Centaurea cyanus
Asteraceae — the same plant family as head lettuce, leaf lettuce, common sunflower, purple coneflower and 12 more here. Relatives share pests and diseases, which is why rotation plans group by family.
Cornflower (Centaurea cyanus) is an annual flower. It wants full sun and pH 6–7.5 soil, with about 0.5–1 in of water weekly. It matures in about 65–90 days from sowing, or 50–70 days from setting out a transplant. Watch for aphids and wilt. Below: its full sourced profile from 5 extension sources, plus a planting calendar timed to your frost dates.
Typical dates for zone 6b — set your zone or ZIP for yours. This calendar assumes the crop is started indoors. Timing is a guide from the crop's sourced growth stages; confirm with your local frost dates and extension before you sow.
What we will not put a number on
We do not give a feeding rate for this crop, and that is deliberate rather than a gap. The figures published by extension services are pounds of nitrogen per acre for a production field — they do not convert safely to a raised bed or a pot without knowing your soil test and your fertilizer's analysis, and guessing errs toward burning roots. It is also why every chart you find online disagrees with the next one.
We give watering as a depth per week rather than gallons per plant, because that is how it is actually measured and how the published figures are written. A gallons-per-plant number depends on your spacing, your soil and whether the plant is in a pot — so it would look more precise than it is.
Site & soil
- Sun
- Full sun
- Soil pH
- 6–7.5est
- Soil texture
- Clay, Loam, Well drained
- Frost tolerance
- Hardy
No published figure for the temperature frost starts to hurt it and the temperature that would kill it. We looked — where a number is missing here it is missing from the research, not skipped. The crop’s frost and heat tolerance above still applies.
The plant
- Mature height
- 1–3 ft
- Mature spread
- 1–2 ft
- Growth rate
- Moderateest
- Spacing in row
- 6–12 in
- Between rows
- 12–18 inest
- Planting depth
- 0.25 in
- Container size
- 1–2 gal — low end is the minimum, high end is betterest
- Support
- Needs staking or a trellis
- Grown from
- Direct sow, Transplant
Water & feeding
- Water needs
- Moderate
- Water per week
- 0.5–1 in/wkest
- Critical water
- Establishmentest
- Feeding
- Low
Timing & fruiting
- Days to maturity
- 65–90 days from seed · 50–70 days from transplantest
- Harvest cues
- First flowers
Planted again for autumn
- Set plants out by
- early Sep typical · zone 6b
50 days to maturity from setting a plant out — that is what our sources measure for this crop, so this is a date for planting out and not a sowing date, counted back from the first frost above. Not published for anywhere in particular: it is your own frost date and this crop's own figure, which is why it works wherever you are. A days-to-maturity figure is a catalog number for a good season rather than a promise, and a cold month moves it.
Edible parts per source: flower.
Compiled from the extensions cited below. Which ones actually show up depends on your region — your extension's local list is the last word.
Different parts differ — the edible part is the flower; the notes below flag other parts or preparations.
PetsNon toxic to cats, Non toxic to dogs, Non toxic to horses
Recorded exactly as the source states it — not medical or veterinary advice. If a person or animal may have eaten a toxic part, call Poison Control (1-800-222-1222) or your vet / the ASPCA line (888-426-4435).
| Variety | Type | Days | Color | What it is known for |
|---|---|---|---|---|
| Black Ball | Tall | 50–70 | Purple | Outsidepride describes this asgets by on less water |
| Blue Boy Heirloom | Tall | 65–75 | Blue | NC State Extension records this asdeer usually leave it alone · gets by on less water · the flowers are edible · draws bees and butterflies · drops seed and comes back on its own |
| Blue Diadem | Tall | 70 | Blue | Select Seeds describes this asgood for cutting and putting in a vase · draws bees and butterflies · drops seed and comes back on its own |
| Classic Fantastic | Tall | 60 | Blue | Harris Seeds describes this asgood for cutting and putting in a vase |
| Classic Magic | Tall | 70 | Bicolor | Select Seeds describes this asdrops seed and comes back on its own |
| Classic Romantic | Tall | 70 | Bicolor | Select Seeds describes this asgood for cutting and putting in a vase |
| Dwarf Blue Midget | Dwarf | 50–70 | Blue | NC State Extension records this asdeer usually leave it alone · gets by on less water · the flowers are edible · draws bees and butterflies · drops seed and comes back on its own |
| Emperor William | Tall | 70 | Blue | Select Seeds describes this asgood for cutting and putting in a vase · drops seed and comes back on its own |
| Florence Mix | Dwarf | 50–70 | Bicolor | NC State Extension records this asdeer usually leave it alone · gets by on less water · the flowers are edible · draws bees and butterflies · drops seed and comes back on its own |
| Frosty Mix | Tall | 50–70 | Bicolor | Premier Seeds Direct describes this asdraws bees and butterflies · good for cutting and putting in a vase |
| Jubilee Gem | Dwarf | 70 | Blue | Select Seeds describes this asan All-America Selections winner · drops seed and comes back on its own · good for cutting and putting in a vase |
| Pinkie | Tall | 70 | Pink | NC State Extension records this asdeer usually leave it alone · gets by on less water · the flowers are edible · draws bees and butterflies · drops seed and comes back on its own |
| Polka Dot Mix | Dwarf | 50–70 | Bicolor | Thresh Seed Co. describes this asdrops seed and comes back on its own |
| Red Boy | Tall | 70 | Pink | Select Seeds describes this asgood for cutting and putting in a vase · draws bees and butterflies · drops seed and comes back on its own |
| Snowman | Tall | 70 | White | Select Seeds describes this asgood for cutting and putting in a vase · drops seed and comes back on its own |
| Tall Blend Mix | Tall | 50–70 | Bicolor | Botanical Interests describes this asgets by on less water · draws bees and butterflies · drops seed and comes back on its own |
- Johnny's Selected Seeds
- Missouri Botanical Garden
- NC State Extension
- University of Florida IFAS Extension
- University of Illinois Extension
We compile bare facts from these university-extension and horticultural sources, never copied prose. 12 of the 19 values on this page carry a citation. The rest are marked est; hover one and it says why — either nobody publishes a figure we could point at, or a person set it and attached no source. Figures vary with climate and seed source; confirm with your local extension before you buy.
Growing more than cornflower? Browse all crops, or grab the spacing calculator and frost date lookup. The GardenTrack app (now in beta) remembers what you planted and where, then tells you what to do and when. Join the beta →