How to grow Bearded Iris

Iris germanica · German Iris

A hardy perennial grown from thick rhizomes, with sword-shaped leaves and large, often fragrant flowers on stalks up to about 1 m in May and June. All parts are toxic to cats, dogs and horses, the rhizomes most of all.

Quick facts

Type	Flower
Family	Iridaceae
Light	Full sun
Soil pH	6–7.5
Frost	tolerates light frost
Germination	180 days
Where it grows	Open ground

When to plant

Plant in autumn, about a month before your first autumn frost, so the roots grow before winter; it flowers or crops the next season.

Dates for your city are on the frost dates page.

Frost dates · When to plant

Care

Open ground

Stage	Watering	Temperature	Feeding
Growth	every 10 days	—	phosphorus and potassium, at the start of the stage
Flowering	every 10 days	—	—

Growing notes

Light

Needs full sun, at least six hours a day; in too much shade it makes leaves but few flowers.

Soil

Well-drained, fertile soil, pH 6.0–7.5. Wet, poorly drained ground causes bacterial soft rot; improve heavy clay with organic matter or plant in a raised bed. Do not mulch over the rhizomes.

Care

Plant rhizomes from July to early September, 30–60 cm apart, with the top of the rhizome at or just below the soil surface. Water well after planting; once established, water only when the top 7–8 cm of soil is dry and avoid wetting the leaves. Feed lightly with a low-nitrogen fertiliser in early spring and a month after flowering; too much fertiliser means fewer flowers. Cut flower stalks to the ground after blooming, clear old leaves in autumn against iris borer, and divide crowded clumps every three to five years in July or August.

Pests and diseases of Bearded Iris

Sources

Figures checked against these sources.