Perennial Flower

When to Plant Irises

Elegant perennial producing sword-shaped leaves and intricate, ruffled blooms in late spring. Bearded irises are the most popular type.

Sun

Full sun (6+ hours)

Water

Moderate — drought tolerant

Days to Harvest

365

Difficulty

beginner

Spacing

18"

Frost Tolerance

high

The Short Answer

Irises are planted in fall, 8 weeks before your first frost date. They need winter cold to trigger their spring bloom. Enter your zip code on our homepage tool for exact dates.

How to Grow Irises

Bearded irises are planted from rhizomes — thick, fleshy root structures that must be planted with the top exposed to sunlight. Burying the rhizome too deep is the most common cause of iris failure. Plant in mid-to-late summer (July-September) for bloom the following spring. After 3-4 years, clumps become congested and bloom decreases; divide immediately after flowering by breaking rhizomes apart and replanting the fans with the most vigorous roots. Iris borer is the most serious pest — the larvae tunnel into rhizomes causing bacterial soft rot. Remove and destroy infected sections immediately.

Fall Planting

Irises are planted in fall, 8 weeks before your average first frost date. , 18" apart.

Growing Tips

Plant rhizomes in mid-to-late summer with the top of the rhizome exposed to sun — don't bury them. Divide every 3-4 years after blooming. Bearded irises are drought-tolerant once established.

Companion Planting

Good companions:

Daylilies Peonies

Irises Planting Dates by State

Click your state for irises planting dates specific to your location:

Note: Planting dates are based on average frost dates from NOAA Climate Normals (30-year averages). Actual conditions vary year to year. Always check your local forecast before planting frost-sensitive crops.

Last reviewed: March 29, 2026