Japanese Iris

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Japanese Iris

These beautiful irises are not as popular in Australia as they deserve to be, probably because they have very particular cultural requirements. However, if you grow them in an acid soil and give them the right amount of water you’ll be rewarded with spectacular blooms from November through to January. You’ll also find that they are virtually pest and disease free. Japanese iris are useful for slightly damp or boggy spots in the garden, but they are not true water plants and must not become waterlogged in winter.

Plant details

Common name: Japanese iris

Botanic name: Iris ensata (previously known as I.kaempferi)

Description: Japanese iris grow from fibrous rhizomes and form a leafy clump to about 1m (3′) tall. The large, flat flowers are borne on spikes up to 2m (6′) tall, and can reach up to 30cm (12″) in diameter when grown in optimum conditions. Colours are limited to white, shades of pink, shades of blue, violet, purple and beet red, but they are often veined, marbled or speckled with a contrasting color. They also come in various patterns and forms, including single, double and multipetalled.

Best climate: Japanese iris will grow in a wide range of climates from cool to subtropical. In inland areas water must not contain alkaline salts. Bore water is unsuitable.

Likes:

full sun to part shade acid soil (pH 5.5-6.0), rich in organic material ample water in spring and summer

Dislikes:

Although they like plenty of summer moisture, Japanese iris can’t tolerate too much water in winter when they’re dormant. Some gardeners overcome these changing needs by growing the iris in containers and keeping the containers in a shallow pond during the summer. In winter the pots are either taken out of the pond, or the pond is drained. This provides the iris with a dry spell, and prevents the rhizomes from rotting.

Care:

Protect from strong winds, which may damage the tall flower stems. Clumps can be left undisturbed for 2-3 years, then lifted, divided and their soil renewed (if growing in a pot). This should be done in May-August when the plants are dormant. The newly divided rhizomes should be planted about 15-20cm (6-8″) apart, with the crowns at ground level. Japanese iris are heavy feeders. Apply a complete fertilizer when rhizomes start to shoot.

Further information:

We filmed our segment at Rainbow Ridge Nursery, 8 Taylors Road, Dural, NSW, 2158. Phone (02) 9651 2857. They supply Japanese iris by mail order in autumn. Prices range from $8-$20, depending on the cultivar.