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Publication #FPS-287

Iris tectorum Japanese Roof Iris1

Edward F. Gilman, David Marshall2

Introduction

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.

General Information

Scientific name: Iris tectorum
Pronunciation: EYE-riss teck-TOR-um
Common name(s): Japanese roof iris
Figure 1. 

Japanese roof iris
Family: Iridaceae
Plant type: herbaceous; ground cover
USDA hardiness zones: 6 through 10 (Fig. 2)
Figure 2. 

Shaded area represents potential planting range.
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

Description

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

Foliage

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

Flower color: white
Flower characteristic: spring flowering

Fruit

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

Culture

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

Other

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.

Footnotes

1.

This document is Fact Sheet FPS-287, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: October, 1999; reviewed June, 2007. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

2.

Edward F. Gilman, professor, Environmental Horticulture Department, David Marshall, agricultural extension agent and program leader, Leon County Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.