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Plant Profile: Japanese Roof Iris (Iris tectorum)

Japenese Roof Iris

Japenese Roof Iris

As a plant collector rather than a garden designer I adore plants that are a bit out of the ordinary and if they come with a good history or story, so much the better. Japanese Roof Iris is one of those plants; it is very delicate and pretty but has an interesting past so it is no wonder that I love it. To make it even more desirable in my garden, it comes with lots of relatives so I can add another species to my collection of the genus Iris.

Iris tectorum is quite distinct from its more familiar relatives, Bearded Iris or Siberian Iris; it has no beard, is crested, and has wide, open flowers due to the fact that the standards lie almost level with the falls. A native of China, it has been grown in Japan for 150 years where its rhizomes were ground and used to paint the faces of Geisha girls white. In China it grew in the ground but when it was taken to Japan it had to be grown on the thatched roofs of houses because the emperor had proclaimed that only rice and vegetables could be grown in the ground due the scarcity of land. (You have to admit, that is a pretty interesting history for a plant).

Type: Herbaceous, evergreen, perennial.

Bloom: Lavender or white flat blooms (6”) in late April or early May.

Size: Flowers on ’20 scapes above 18” foliage.

Light: Full sun preferred but some shade tolerated (unlike many other iris)

Soil: Rich, moist, well drained and slightly acid.

Fertilizer: One to two tablespoons complete fertilizer (10-10-10) before blooming.

Hardiness: Zones 4-10.

Care: Spring fertilization and heavy mulch in spring and fall.

Pests and Diseases: Protect against slugs.

Propagation: Division of rhizomes immediately after flowering.

Companion plants: Plant in drifts at the front of the border or in rock gardens with similar plants; in a shady area combines well with Foam Flower (Tiarella), Fringed Bleeding Heart, and Brunnera.

Comments: This species is a welcome addition to a shade garden.

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