About
Iris tectorum, the Japanese roof iris, is an upright rhizomatous perennial to around 40 cm with fans of sword-shaped, ribbed, mid-green leaves. In late spring and early summer, pale violet-blue flowers with strongly ruffled edges to the falls and standards are produced � their common name comes from their traditional planting on thatched rooftops in Japan. An outstanding, easy and ornamental iris for a sunny, well-drained border.
About the genus
Iris are rhizomatous or bulbous perennials with narrow, often sword-shaped leaves and erect stems bearing flowers with three large, spreading or pendent fall petals alternating with three erect, often smaller, standard petals in late winter, spring or early summer. One of the most varied and spectacular of all plant genera, encompassing everything from tiny bulbous species to tall bearded border irises.
Growing conditions
SunlightFull sun, Partial shade
Soil typeLoam, Sand
Soil pHNeutral, Acid
Soil moistureWell-drained
AspectSouth-facing, East-facing, West-facing
ExposureSheltered
UK hardinessH6
Plant details
Plant typeHerbaceous Perennial
HabitClump forming
FoliageDeciduous
Height0.5-1 metres
Spread0.1-0.5 metres
Time to full height2-5 years
Suggested usesCity and courtyard gardens, Cottage and informal garden
Native toChina
ToxicityHarmful if eaten. Wear gloves and other protective equipment when handling. Pets: Harmful if eaten. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Care notes
CultivationGrow in well-drained, fertile, neutral to slightly acid soil in full sun
PruningRemove spent flower stems in summer, and any dying foliage in autumn
PropagationPropagate by division, see dividing iris for more detailed advice
Pest resistanceMay be susceptible to slugs, snails and thrips
Disease resistanceMay be susceptible to aphid-borne viruses, bacterial soft rot and grey moulds; see Iris diseases