Corncockle (Agrostemma githago) - How to Grow & Care Guide

Plant Snapshot

Common Name: Corncockle
Latin Name: Agrostemma githago
Hardiness Zones: Grown as an annual across many climates; survives winters as seed rather than as a hardy perennial. In colder zones it will not overwinter as a plant but will reseed. In warm climates it may self seed and persist.
Typical Height: 24–36 in (60–90 cm)
Typical Spread: 6–12 in (15–30 cm)
Bloom Period: Summer, typically June–August in temperate Northern Hemisphere
Soil Preferences: Lean to average, well drained soils. Tolerates poor and dry soils. Waterlogged or heavy clay soils are problematic and can reduce vigor and flowering.
Light Preferences: Full sun for best flowering. Tolerates light afternoon shade but will produce fewer blooms in deep shade.
Toxicity: All parts considered toxic if ingested, especially seeds. May cause gastrointestinal distress and more serious poisoning in larger ingestions. Handle seeds and plant material with care and keep away from children and livestock.
Propagation: Direct sow outdoors in autumn or spring. Starts can be sown indoors for earlier bloom. Readily self seeds and may persist from volunteers.

Key Facts

An annual wildflower historically associated with cereal grain fields
Produces cup shaped pink to magenta flowers held above the foliage
Typically grows upright and produces a single main stem with opposite leaves
Self seeds readily and can naturalize in suitable sites
Seeds and other plant parts are considered toxic if ingested
Prefers well drained soil and performs best in full sun
Often used in cottage gardens and wildflower mixes

Corncockle (Agrostemma githago) is an annual wildflower with cup shaped pink to magenta flowers held above a single upright stem. It brightens cottage borders and wildflower mixes but self seeds readily and its seeds are poisonous if eaten.

Identification

Upright annual forming a single main stem with opposite leaves. Mature plants typically reach about 242 in (6090 cm) in a season and spread roughly 62 in (150 cm) per plant. Flowers are cup shaped and pink to magenta and appear in summer.

Where to grow and common uses

Grows best in full sun on well drained soil and tolerates lean or dry soils that limit more demanding ornamentals. Use in cottage garden beds, mixed annual borders and wildflower meadows where volunteers are acceptable. It will produce fewer blooms in deep shade.

Planting and timing

Direct sow outdoors in autumn or spring. Seeds can be started indoors to get an earlier bloom but transplant carefully to avoid root disturbance. Space plants about 62 in (150 cm) apart to match their natural spread. Local sowing dates shift with climate so match timing to your last frost and local conditions.

Soil and watering

Prefer well drained, average to poor soils and avoid waterlogged heavy clay which reduces vigor and flowering. Once established plants tolerate dry conditions better than constantly wet sites. Good drainage encourages stronger stems and more blooms.

After flowering and controlling spread

Plants set seed readily and will naturalize where allowed to drop seed. Remove or cut off seed pods before they ripen to limit volunteers. To tidy beds cut stems to the ground after flowering. Leave some seed heads if you want plants to return the following year.

Safety and toxicity

All parts are considered toxic, especially the seeds. Keep plant material and seeds away from children and livestock and consult a poison control center or veterinary toxicology source for specific advice on suspected ingestion.

Frequently asked questions

How fast does Corncockle grow?: From seed it grows through the season to roughly 246 in (6090 cm) tall; actual speed depends on sowing date, light and soil fertility.
When does Corncockle bloom?: Flowers appear in summer, typically June through August in temperate northern hemisphere climates. Exact timing varies with sowing date and local climate.
Will Corncockle come back next year?: Plants are grown as annuals and survive winters as seed rather than as hardy perennials. It will return only where seed germinates the following season.
Are Corncockle seeds poisonous?: Yes. Seeds and other plant parts are considered toxic if ingested. Seek professional guidance for suspected poisoning.
How do I stop Corncockle from spreading?: Prevent reseeding by deadheading or removing seed pods before they ripen and by pulling volunteer seedlings in spring.