Illustration
Photo credits and licenses
Real photographs from naturalists and photographers worldwide, each used under its own license. Credit: Photo by Bartosz Czołczyński / iNaturalist (CC0), Photo by akimuzuk / iNaturalist (CC0), Photo by akimuzuk / iNaturalist (CC0) and Photo by akimuzuk / iNaturalist (CC0). How photos are sourced →
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 1.5 ft wide at maturity, in roughly 1 year (a house reading).
Pets
- Not yet checked for pets.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
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
Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. Each fact above carries its own mark. 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 adult1.5 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 1.5 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, water, bloom months and color and trait tags were checked against 12 published sources on October 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 Gardenheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- NC State ExtensionCentaurea cyanusheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- roundstoneseed.comRoundstone Native Seed, Tall Blue Cornflower (Centaurea cyanus)height, hardiness zones, sun, water, bloom months and color and trait tags
- University of Illinois ExtensionBachelor's Buttonheight, sun, water, bloom months and color and trait tags
- Missouri Botanical GardenCentaurea cyanusheight, spread, hardiness zones, sun and trait tags
- RHSCentaurea cyanusheight, spread, sun and bloom months and color
- Missouri Department of Conservationcornflower, bachelor's buttonheight, bloom months and color and trait tags
- purdue.eduPurdue University Consumer Horticulture, Indiana Yard and Gardenheight, bloom months and color and trait tags
- botanicalinterests.comBotanical Interests, Tall Blend Bachelor's Button Seedsheight, sun and trait tags
- Johnny's Selected SeedsCentaurea Key Growing Informationsun and trait tags
- Chicago Botanic Gardentrait 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 7 varieties across 4 colors
Same genus, similar care - pick the color you are growing.
Across the group, bloom runs from May through July: Amethyst Dream Bachelor Button opens first (May) and Bachelor's Button is the last to finish (July).
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) |
|---|---|---|---|---|---|
| Amethyst Dream Bachelor | Purple | May–Jun | Zones 3–8 | Full sun | 20 in × 24 in |
| Amethyst in Snow | White | May–Jun | Zones 3–8 | Full sun | 16 in × 24 in |
| Bachelor'sthis page | Blue | May–Jul | Zones 2–11 | Full sun | 2.5 ft × 1.5 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.
Texas Mountain Laurel
Shares full sun and low water; blooms in early spring, before this one opens; both are strong pollinator plants, and they feed in different months; 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; 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.
Fountain Grass
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.
Dotted Blazing Star
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.
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.
Ironweed
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.
Yaupon Holly
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; evergreen, so the bed keeps its shape through winter.
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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.