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Bachelor's Button
Centaurea cyanus
Bachelor's Button blooms from May through July.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Bachelor's Button
Plant it in full sun. It prefers low water. It is hardy in USDA zones 2–11. Expect it to reach about 2.5 ft tall and 1 ft wide at maturity, in roughly 1 year (not yet checked).
No toxicity note is on file for Bachelor's Button. That is not a clearance: check its safety for people and pets before planting.
What was checked
Mature height and spread, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not, and each fact above says which. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Bachelor's Button
Wait until all danger of frost has passed, then plant out Bachelor's Button into warm soil; in most zones that means late spring. Planted then, it flowers from May to July.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in April. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Bachelor's Button get?
2.5 fttall5 ft 7 inan adult1 ftwideSee Bachelor's Button in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Bachelor's Button
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Bachelor's Button about 1 ft apart, center to center, so each plant has room to reach its full width.
Add Bachelor's Button to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Bachelor's Button's height, spread, hardiness zones, sun and trait tags were checked against 10 published sources on July 29, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical GardenCentaurea cyanusheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionCentaurea cyanusheight, spread, hardiness zones, sun and trait tags
- botanicalinterests.comBotanical Interests, Tall Blend Bachelor's Button Seedsheight, sun and trait tags
- RHSCentaurea cyanusheight, spread and sun
- roundstoneseed.comRoundstone Native Seed, Tall Blue Cornflower (Centaurea cyanus)height, sun and trait tags
- University of Illinois ExtensionBachelor's Buttonheight, sun and trait tags
- Johnny's Selected SeedsCentaurea Key Growing Informationsun and trait tags
- Missouri Department of Conservationcornflower, bachelor's buttonheight and trait tags
- purdue.eduPurdue University Consumer Horticulture, Indiana Yard and Gardenheight and trait tags
- westcoastseeds.comWest Coast Seeds, How to Grow Centaurea Cornflowerssun
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 5 varieties across 4 colors
Same plant, same care - pick the color you are growing.
Compare every variety in the Bachelor's Button group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Bachelor'sthis page | Blue | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1 ft |
| Black Ball | Red | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1 ft |
| Pink | Pink | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1 ft |
| Purple | Purple | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1 ft |
| Red Boy | Red | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1 ft |
| White | White | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1 ft |
Good to know about Bachelor's Button
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Worth knowing
A peer-reviewed meadow study ranked it the top annual for nectar sugar, about 896 micrograms per floral unit per day, supplying about 33 percent of nectar in annual plantings. per PLOS ONE
Garden favorite or invasive weed
It reseeds freely, a welcome self-sower in a managed bed but listed as invasive in Georgia, West Virginia, and Tennessee. Deadhead before seed drop and check your local list. per Invasive Plant Atlas and Tennessee Invasive
Edible petals
The petals are edible, a common garnish scattered fresh or dried over salads, desserts, and drinks, and used in herbal tea blends. per NC State and Longwood
Sow in cool weather
It is a cool-season annual that fades as summer heat arrives. Sow in cool soil, early spring or autumn in mild climates, for the best, longest bloom. per NC State
Lean soil, drought tolerant
Thrives in lean, even poor, dry ground, so do not enrich the soil. Rich soil or shade just makes stems leggy and floppy. It is genuinely drought tolerant. per NC State
Seed heads feed birds
Deadheading prolongs bloom and curbs self-seeding, but the seed heads feed goldfinches. Where it is not invasive, leave a few heads to support songbirds. per NC State and Longwood
What pairs well with Bachelor's Button
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Goldenrod
Shares full sun and low water; blooms in late summer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.
Autumn Joy Sedum
Shares full sun and low water; blooms in late summer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.
Perennial Sunflower
Shares full sun and low to moderate water; blooms in late summer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.
Switchgrass
Shares full sun and low water; blooms in late summer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.
Rosemary
Shares full sun and low water; opens in early spring and overlaps into this one's season; both are strong pollinator plants; evergreen, so the bed keeps its shape through winter.
Little Bluestem
Shares full sun and low water; blooms in late summer as this one finishes; its seed heads stand through winter, for structure and the birds; taller at 3.5 ft, for the layer behind it.
Fountain Grass
Shares full sun and low water; blooms in late summer as this one finishes; its seed heads stand through winter, for structure and the birds; taller at 3.5 ft, for the layer behind it.
Grape Hyacinth
Shares full sun and low water; blooms in early spring, before this one opens; both offer pollinator forage, in different months; lower at 8 in, for the front of the border.
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.