Heirloom

Black Button

Centaurea cyanus

Photo: Kersti · Wikimedia Commons · (CC BY-SA 4.0)

Harvest

65-75d

Days to harvest

📅

Sun

Full sun to partial shade

☀️

Zones

2–11

USDA hardiness

🗺️

Height

1-3 feet

📏

Planting Timeline

Zone:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Start Indoors

Transplant

Direct Sow

Start Indoors

Transplant

Direct Sow

Showing dates for Black Button in USDA Zone 7

All Zone 7 flower →

Zone Map

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Black Button · Zones 2–11

What grows well in Zone 7? →

Growing Details

Difficulty

Easy

Spacing12-18 inches

SoilWell-drained soil, tolerates poor to average conditions

WaterModerate, drought tolerant once established

SeasonWarm season annual

FlavorBland, mildly floral taste with subtle sweet notes.

ColorDeep blue-black

Size1-1 1/2"

Zone-by-Zone Planting Calendar

Zone	Indoor Start	Transplant	Direct Sow	Harvest
Zone 3	April – May	June – July	June – August	—
Zone 4	March – April	June – June	June – July	—
Zone 5	March – April	May – June	May – July	—
Zone 6	March – April	May – June	May – July	—
Zone 7	February – March	April – May	April – June	—
Zone 8	February – March	April – May	April – June	—
Zone 9	January – February	March – April	March – May	—
Zone 10	January – January	February – March	February – April	—
Zone 1	May – June	July – August	July – September	—
Zone 2	April – May	June – July	June – August	—
Zone 11	January – January	January – February	January – March	—
Zone 12	January – January	January – February	January – March	—
Zone 13	January – January	January – February	January – March	—

Succession Planting

Direct sow every 2–3 weeks from April through early June in zone 7, stopping once daytime highs are regularly hitting 80°F — cornflowers bolt and go patchy in sustained heat. For a longer window, start your first round indoors in late February and transplant out in April, then follow with direct-sown rounds behind it. You'll get a solid 6–8 weeks of cut flowers before the heat shuts things down.

For a fall flush, direct sow again in late August once temperatures start backing off. Germination is reliable at soil temps between 60–65°F, so don't rush the fall sowing — seed sitting in warm soil tends to stall.

Complete Growing Guide

Upright plants produce abundant double and semidouble 1-1 1/2" blooms. Prefers cool temperatures. Also known as cornflower, garden cornflower, and bachelor's buttons. Edible Flowers: The petals are used to decorate desserts. Centaurea is also a popular choice for brightening up salad mix. Flavor is bland and mildly floral. According to Johnny's Selected Seeds, Black Button is 65 - 75 days to maturity, annual, open pollinated. Notable features: Use for Cut Flowers and Bouquets, Edible Flowers, Attracts Beneficial Insects.

Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: Clay, High Organic Matter, Loam (Silt). Soil pH: Acid (<6.0), Alkaline (>8.0), Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 1 ft. 0 in. - 3 ft. 0 in.. Spread: 1 ft. 0 in. - 2 ft. 0 in.. Spacing: Less than 12 inches. Growth rate: Medium. Maintenance: High. Propagation: Seed.

Harvesting

Black Button reaches harvest at 65 - 75 days from sowing per Johnny's Selected Seeds. Expect 1-1 1/2" at peak. As an annual, harvest continues until frost ends the season.

Finely hairy, straw-colored at maturity with a tuft of short, stiff, light brown bristles at the tip.

Color: Cream/Tan. Type: Achene. Length: < 1 inch. Width: < 1 inch.

Harvest time: Fall

Edibility: Edible

Storage & Preservation

Fresh Black Button cornflowers should be stored upright in a vase with water at room temperature (65-70°F) away from direct sunlight, where they'll last 7-10 days. For longer storage, keep stems in cool water in the refrigerator (35-40°F) with 60-70% humidity for up to 2 weeks. For preservation: (1) Air-dry bundles hanging upside-down in a cool, dark, well-ventilated space for 2-3 weeks to use in dried arrangements; (2) Press petals between paper for 1-2 weeks to preserve for culinary decoration and herbal use; (3) Freeze petals in ice cube trays with water for decorative and culinary applications lasting several months.

History & Origin

Black Button is open-pollinated, meaning seed saved from healthy plants will produce true-to-type offspring. Listed in the Johnny's Selected Seeds catalog.

Origin: Western Asia, Europe

Advantages

+Produces abundant double blooms on upright, compact plants
+Ready to harvest in just 65-75 days from planting
+Edible petals add visual appeal to desserts and salads
+Thrives in cool temperatures, ideal for spring and fall
+Easy to grow with minimal gardening experience required

Considerations

-Black petals may lack visual impact compared to bright colors
-Bland flavor profile limits culinary appeal in dishes
-Prefers cooler climates, struggles in hot summer regions

Companion Plants

Marigolds and nasturtiums pull the most weight here. French marigold types like 'Petite Gold' push out aphids and whiteflies through root secretions, and since Black Button cornflowers are strong hoverfly and lacewing attractors, the two plants reinforce each other's pest suppression without much effort on your part. Nasturtiums work as a trap crop — aphids will pile onto them before touching your cornflowers, which buys you time to deal with the problem before it spreads. Sweet alyssum and catmint round out the bed by drawing in parasitic wasps that patrol everything within a few feet.

Black walnut is the one plant to keep off the same property entirely if you can. Walnut roots release juglone — a compound that moves through soil and stunts or kills a wide range of plants — and cornflowers are sensitive enough that proximity alone can cause unexplained wilting and dieback. Sunflowers are less dramatic but still a bad match: their canopy height (some varieties hit 6–8 feet) shades out cornflowers that need 4–6 hours of direct sun to bloom well, and their roots compete aggressively for the same shallow moisture zone.

Plant Together

Marigolds

Repel aphids, whiteflies, and nematodes while attracting beneficial insects

Nasturtiums

Act as trap crops for aphids and cucumber beetles, protecting nearby plants

Sweet Alyssum

Attracts beneficial insects like lacewings and hover flies for pest control

Lavender

Repels moths, fleas, and mosquitoes with its strong fragrance

Cosmos

Attracts pollinators and beneficial predatory insects while providing visual contrast

Catmint

Deters ants, aphids, and rodents while attracting beneficial pollinators

Zinnia

Attracts butterflies and beneficial insects while complementing growth habits

Parsley

Attracts beneficial insects and provides ground cover without competing for resources

Keep Apart

Black Walnut

Produces juglone toxin that inhibits growth and can kill sensitive flowering plants

Eucalyptus

Releases allelopathic compounds that suppress growth of nearby plants

Sunflowers

Compete aggressively for nutrients and water, may stunt growth of smaller flowers

Pests & Disease Resistance

Common Pests

Spotted cucumber beetle, flea beetle, spider mites

Diseases

Powdery mildew, rust, leaf spot

Troubleshooting Black Button

What you'll see, why it happens, and what to do about it.

White powdery coating spreading across leaves and stems, usually showing up after a stretch of warm days and cool nights

Likely Causes

Powdery mildew (Erysiphe cichoracearum) — a fungal infection that thrives in humid air with poor circulation
Crowded planting at less than 12 inches apart, trapping moisture between plants

What to Do

1.Cut out and trash the worst-affected stems — don't compost them
2.Spray remaining foliage with a diluted baking soda solution (1 tablespoon per gallon of water) every 7 days
3.Next season, stick to 12–18 inch spacing and avoid overhead watering

Small ragged holes chewed in young leaves and petals, especially on seedlings under 4 inches tall

Likely Causes

Flea beetles (Phyllotreta spp.) — tiny, fast-jumping beetles that riddle foliage with shot-hole damage
Spotted cucumber beetle (Diabrotica undecimpunctata) feeding on open flowers

What to Do

1.Cover seedlings with row cover until plants hit 6 inches — flea beetles do the most damage early
2.Direct sow into the garden rather than transplanting when possible; established plants handle flea beetle pressure far better than tender transplants

Frequently Asked Questions

How long do Black Button cornflowers last after cutting?▼

Fresh Black Button cornflowers typically last 7-10 days in a vase with water at room temperature. To extend their vase life to 2 weeks, refrigerate them at 35-40°F between uses. Change the water every 2-3 days and re-cut stems at an angle to improve water absorption and longevity.

Is Black Button cornflower good for beginners?▼

Yes, Black Button cornflower is excellent for beginners. It's classified as an easy-to-grow heirloom variety that requires minimal maintenance. The plants are upright, produce abundant blooms, and are forgiving of various conditions as long as they receive 4-6+ hours of sunlight daily. Perfect for new gardeners.

Can you grow Black Button cornflowers in containers?▼

Yes, Black Button cornflowers grow well in containers. Use well-draining potting soil in a pot at least 8-10 inches deep. Place containers in full sun to partial shade and water regularly. Container growing allows you to position plants closer together than ground spacing for a fuller, more abundant display of blooms.

What does Black Button cornflower taste like?▼

Black Button cornflower petals have a bland, mildly floral taste with subtle sweet notes. The flavor is quite delicate and not overpowering, making them ideal for garnishing desserts and salads without dominating the dish. The petals are edible and food-safe when grown without pesticides.

When should I plant Black Button cornflowers?▼

Direct sow Black Button cornflower seeds after the last frost date in your region, pressing them lightly into the soil. They germinate in 7-10 days and reach harvest size in 65-75 days. For earlier blooms, start seeds indoors 6-8 weeks before the last spring frost and transplant seedlings after frost danger passes.

Are Black Button cornflowers the same as bachelor's buttons?▼

Yes, Black Button is a variety of cornflower (Centaurea cyanus), also commonly called bachelor's buttons, garden cornflower, or simply cornflower. These names are used interchangeably. The 'Black Button' variety is prized for its double and semidouble deep-colored 1-1.5 inch blooms produced abundantly on upright plants.