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Common Name: Roof Iris

General Information

Iris tectorum is a Evergreen Perennial up to 0.30 metres tall.
It is harvested from the wild for local use as a food.

Known Hazards

Many plants in this genus are thought to be poisonous if ingested, so caution is advised[]. The roots are especially likely to be toxic[].
Plants can cause skin irritations and allergies in some people[].

Botanical References

, ,

Range

E. Asia - China, Japan.

Habitat

Grows wild on shady rocky slopes and in scrub, it is also found planted on thatched roofs in Japan. Forest margins, sunny banks, meadows, damp places, beside water to 3500m[].

Properties

Edibility Rating
Habit	Evergreen Perennial
Height	0.30 m
Pollinators	Insects
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

Prefers a well-drained loam rich in leafmold with plenty of moisture in summer and an open sunny position[, , , ]. Requires a really well-drained soil that is dry rather than damp, and a hot sunny position[]. Prefers a lime-free soil but succeeds in most good soils and in partial shade[]. Succeeds in dry soils and, once established, is drought tolerant[].
Cultivated for its edible root in Japan[]. There are some named varieties, selected for their ornamental value[]. In China the plants are grown on the roofs of houses[].
Plants do not flower so freely in cultivation in Britain. In their native habitat they experience cold dry winters and warm wet summers[]. It is best to lift the plants in October, store them in sand in a cool frost free place over winter and replant in March[].
Members of this genus are rarely if ever troubled by browsing deer or rabbits[].

Edible Uses

Root - an edible starch is said to be extracted from it[, , ]. Some caution is advised since there are reports that the plant might be poisonous. Perhaps the extracted starch is edible.

Medicinal

None known

Other Uses

None known

Propagation

Seed - best sown as soon as it is ripe in a cold frame. Stored seed should be sown as early in the year as possible in a cold frame. Stored seed does not require cold conditions in order to stimulate germination. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse or cold frame for their first year. Plant out into their permanent positions in late spring or early summer.
Division, best done in mid summer after flowering. Very easy, larger clumps can be replanted direct into their permanent positions, though it is best to pot up smaller clumps and grow them on in a cold frame until they are rooting well. Plant them out in the spring.