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Iris tectorum Japanese Roof Iris1

Edward F. Gilman and David Marshall 2


Japanese roof iris has wonderfully textured, light-green foliage emerging directly from the ground in dense clumps (Fig. 1). It is closely related to the native crested iris. It grows 12 to 18 inches tall, producing blue flowers in the spring. Flowers are displayed in a showy fashion within the clump of foliage.

Figure 1. Japanese roof iris.
Figure 1.  Japanese roof iris.

General Information

Scientific name: Iris tectorum
Pronunciation: EYE-riss teck-TOR-um
Common name(s): Japanese roof iris
Family: Iridaceae
Plant type: herbaceous; ground cover
USDA hardiness zones: 6 through 10 (Fig. 2)
Planting month for zone 7: year round
Planting month for zone 8: year round
Planting month for zone 9: year round
Planting month for zone 10: year round
Origin: not native to North America
Uses: border; mass planting; ground cover; edging
Availability: somewhat available, may have to go out of the region to find the plant

Figure 2. Shaded area represents potential planting range.
Figure 2.  Shaded area represents potential planting range.


Height: 1 to 1.5 feet
Spread: 2 to 3 feet
Plant habit: upright
Plant density: moderate
Growth rate: moderate
Texture: coarse


Leaf arrangement: most emerge from the soil, usually without a stem
Leaf type: simple
Leaf margin: entire
Leaf shape: linear
Leaf venation: parallel
Leaf type and persistence: semi-evergreen; evergreen
Leaf blade length: 12 to 18 inches
Leaf color: green
Fall color: no fall color change
Fall characteristic: not showy


Flower color: white
Flower characteristic: spring flowering


Fruit shape: unknown
Fruit length: unknown
Fruit cover: unknown
Fruit color: unknown
Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: not applicable
Current year stem/twig color: not applicable
Current year stem/twig thickness: not applicable


Light requirement: plant grows in part shade/part sun
Soil tolerances: acidic; sand; loam; clay
Drought tolerance: high
Soil salt tolerances: unknown
Plant spacing: 24 to 36 inches


Roots: not applicable
Winter interest: no special winter interest
Outstanding plant: plant has outstanding ornamental features and could be planted more
Invasive potential: not known to be invasive
Pest resistance: long-term health usually not affected by pests

Use and Management

The plant is grown and used for its foliage effect as well as the flower display. Many people may not notice the flowers nestled within the foliage clumps, but it is hard to miss the coarse-textured foliage. It is well suited for planting in mass in front of a shrub border, or as a ground cover. On 2-foot centers, a thick ground cover can be formed in about 2 years.

Although full sun is tolerated if soils stay moist, a well-drained, partially shaded location provides the best habitat for Japanese roof iris. Plants can be allowed to dry out in a shaded location with little damage to foliage or flowers. As with other irises, overfertilization will encourage foliage growth at the expense of flowers. A light application once each year should be enough to maintain good growth and a reliable flower display.


1. This document is FPS-287, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date October 1999. Reviewed February 2014. Visit the EDIS website at
2. Edward F. Gilman, professor, Environmental Horticulture Department; and David Marshall, agricultural Extension agent and program leader, UF/IFAS Extension Leon County; UF/IFAS Extension, Gainesville, FL 32611.

Publication #FPS-287

Date: 8/5/2015

      Organism ID


      • Gail Hansen de Chapman