Japanese Iris Planting Guide

Few plants offer the landscaping grace of Japanese irises. Described as "floral butterflies" when in bloom, these perennials also provide strong vertical design elements in the form of straight, upright foliage. If you haven't tried these, consider doing so. Odds are good you'll like them. A lot.

Choosing a Site

Japanese irises grow best in full sun. In the hottest parts of the country, select a site that enjoys some shade in the afternoon. These plants are among the few perennials that will thrive in soil that is not well drained. Feel free to plant them at the edge of a pond or stream.

Soil Prep

Moderately fertile soil to rich humusy soil works well for Japanese irises. If your soil is lean, add some compost, decomposed manure or other enriching amendment prior to planting. Japanese irises also do very well in moist, acidic soils.

When to Plant Japanese Irises

Plant Japanese irises outdoors in spring when frost danger has past and soil has warmed. These perennial plants can manage cold temperatures fine when establish, but during their settling in period they need protection from freezing.

How to Plant

Soaking your iris plants in a bucket of water for a few hours prior to planting helps reduce transplant stress. Do not allow the roots to dry out while transplanting. Plant iris clumps with the junction between the roots and the top positioned 1” below the soil surface. If the clump sits in a slight depression this tends to capture water and keep the soil moist. 

Refill around plant with soil, tap down to eliminate any big air pockets and water well to settle the soil around the roots. Keep soil moist, but not soggy wet, while plants are establishing. Do not cover with mulch.

Plant Japanese irises about 10-12” apart.

During the Season

Japanese irises are heavy feeders and an application of a balanced fertilizer in spring prior to flowering is beneficial. This isn’t necessary the first season, but is a good idea thereafter. You may choose to deadhead (remove spent flowers) to keep the plants looking their best. Feel free to cut flowers to enjoy indoors. While they aren’t long lasting, their textures, colors and patterns are gorgeous.

Insider Tips

  1. If you have a water feature in your landscape, Japanese irises are perfect additions. Plant on the water’s edges, where the flowers can reflect in the water.
  2. Mulching helps to keep the soil around your irises root cool, moist and weed-free. Keep the mulch pulled back 2" from the plant stems.
  3. After blooming, the narrow upright foliage of these irises provides a strong vertical accent in the garden.
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Success Snapshot

Light: Full sun to partial sun

Soil: Average

Depth: Plant 1" below soil level

Water: Plants like moist settings

Uses: Perennial gardens, moist meadows

Tip: Stop to explore the intricate blooms

GUIDE: Japanese Iris Planting Guide

They Start Out Looking Like This: