Growing Agrostemma (Corn Cockle): A Complete Profile

By Growing Home Greens Team · August 10, 2026

Agrostemma, better known as corn cockle, has a history as an unwanted weed in European grain fields before it found a second life as a deliberately grown cut flower. Its delicate, magenta-pink blooms on tall, wiry stems have the airy, cottage-garden look that’s hard to get from a sturdier, more structured flower.

Sowing it for cool weather

Direct-seeding is the recommended method, sown 1/8 inch deep as soon as the soil is workable, or start indoors 4 to 5 weeks before your last frost. Germination takes 7 to 14 days at 60-70°F. Thin plants to 6 to 9 inches apart once the first true leaves appear; mature plants reach 24 to 36 inches tall.

Agrostemma performs best in cool conditions, blooming in July and August from an early spring sowing. For continuous bloom rather than one early flush, sow a new round every 2 to 3 weeks through midsummer.

Harvest early in the spray

Cut for a vase when just 1 to 2 flowers in a spray have opened; the rest continue opening after cutting, which extends the useful bloom window well past the initial harvest.

Agrostemma has no recorded companions or antagonists in our data. See the full companion guide for agrostemma for how it’s tracked. At 2 plants per square foot, it works well in a dedicated cutting row in the Garden Designer, timed for the cool part of the season.

Source: Agrostemma (Corn-Cockle): Key Growing Information, Johnny’s Selected Seeds.

Companion planting guide for Agrostemma (Corn Cockle) · Find your planting dates

Typically viable in USDA zones 2-11. Not sure your zone? Look it up by ZIP code.

Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Agrostemma (Corn Cockle) tolerates either.

See exact start-indoors, direct-sow, and harvest dates for your zone →

How many Agrostemma (Corn Cockle) plants fit per square foot?

Spacing: 2 per square foot (square-foot-gardening spacing). Mature height: 2-3 ft.

Varieties worth considering

Straight-species agrostemma (Agrostemma githago): Johnny's Selected Seeds sells this species in a couple of named color strains (the classic magenta-pink and a paler 'Ocean Pearl' white); the growing requirements are consistent across them, so the species itself covers what matters for care. (source)
'Purple Queen' agrostemma (best for: classic magenta cut flower): Johnny's Selected Seeds describes this as an elegant cut flower for early-season production, the classic deep-magenta corn cockle color. (source)
'Blossom Pearl' agrostemma (best for: blush pink color): Johnny's Selected Seeds lists this as producing blush pink blooms on long graceful stems, a softer color option than the standard magenta or white forms. (source)

Cited from the source shown next to each variety. We haven't grown these ourselves yet, so treat this as a research-backed starting point, not a personal endorsement.

Where to buy agrostemma seeds

As an Amazon Associate we earn from qualifying purchases. Some links on this page also go to other retailers we may earn a commission from as an affiliate, at no extra cost to you. We only recommend products with a genuine consensus of positive, independent reviews. See the sources cited on each item.

See it growing

Search YouTube for "growing agrostemma (corn cockle)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)

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Growing Agrostemma (Corn Cockle): A cottage-garden annual with delicate, magenta-pink blooms on wiry stems, an old European grain-field weed now grown deliberately as a cut flower.

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