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Japanese Iris — a Popular Perennial for Boggy Sites

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I. ensata Robert E. Lyons ©

I. ensata
Robert E. Lyons ©

A popular perennial for wet and boggy sites is the Japanese iris, Iris ensata. This beauty with spectacular flowers and sword-shaped foliage provides the exclamation point in late spring and early summer gardens. Iris ensata, formerly known as I. kaempferi, blooms later than the bearded iris hybrids, with huge 8- to 10-inch-wide flat blossoms, often mottled or delicately patterned in shades of white, violet, blue or purple. The flowers are exquisite but fragile and easily damaged by hot sun, dry wind or heavy rains. Japanese irises are excellent for the damp banks of a pond or stream or in rain gardens. They also grow in a rich, moist, fertile bed that has been generously amended with organic matter, particularly when acidic in nature. Combined with masses of Japanese primroses, they make any garden site quite lovely.

Hundreds of cultivars are available in many color combinations. Most have very small standards (the small projecting petal-like structure near the flower’s center) and wide, flat falls (the three very colorful droopy structures); some are double with a soft mass of petals. I. laevigata, a close cousin, also has spectacular large flowers in shades of white or purple. It needs constant moisture around the roots and does best in shallow water.

I. ensata Robert E. Lyons ©

I. ensata
Robert E. Lyons ©

Plant Japanese irises in early fall, setting the rhizomes about 2 inches deep and 12 to 18 inches apart. Divide every 3 to 4 years, if desired, but it is not necessary to the overall good health of the plant. Remove faded flowers if desired.

Another desirable feature of Japanese irises is their relative resistance to the iris borer, a damaging pest that can lead to soft, dead rhizomes in bearded iris,Iris x germanica. They do not grow as fast as related species that are popular in home gardens, and they may respond adversely to minor changes in their surrounding growing conditions, like reduced sun, drier soils and loss of acidity.

Japanese irises are not found extensively throughout the JC Raulston Arboretum (JCRA) but they contribute to the overall palette of all Iris species that can be enjoyed through the year at the JCRA.

Willie Earl Wilson