Japanese irises possess a bold beauty unmatched by any other herbaceous perennial, yet for years they have been overlooked by many gardeners.
This neglect is caused by confusion about the names of varieties and misconceptions about the cultural requirements of the species.
Developing And Perfecting Irises
For more than 150 years, Japanese gardeners have been developing and perfecting irises, but no accurate records were kept.
When these irises were imported in 1869, they brought a chaotic nomenclature intensified by Japanese spellings and translations.
Gardeners were confronted with names like “Band of Clouds” for Kimono-is, “Early Summer Rainfall” for Samidare, “Cherry Blossoms in every Direction” for Yama-za-kura, and “Love of Husband” for Sofu-no-hoi. It was poetic but difficult to remember and cumbersome to print in catalogs.
There was confusion with scientific names. For example, the Japanese iris is now commonly accepted as Iris kaempferi, but it has also been called I. laevigata and I. laevigata var. kaempferi.
Botanically, kaempferi is differentiated from laevigata by a distinct midrib in the leaf.
Japanese Irises Differ From Beardless Sorts
The Japanese irises differ from other beardless sorts in that they require more water and acid soil. Herein lies the second confusion that has plagued them.
In Japan, they are grown in rice fields or other depressed locations, which are flooded before and during the blooming season, and it has been assumed they won’t grow successfully unless periodically flooded. This is not so.
Japanese irises can be easily grown in a perennial American border, provided they are given rich loam soil and sufficient water during their growing season.
Enriching Soil
Since the iris plants are ravenous feeders, enrich the soil at planting time with peat moss, leaf mold, or compost, using two to three shovels per plant.
Cow manure (an acceptable pulverized commercial brand) should also be added to the soil.
A pH of 5-7 is needed. If necessary, aluminum sulfate may be added to achieve this. An annual application of a complete commercial fertilizer recommended for azaleas and hollies will also benefit growing fine irises.
Best Time For Planting or Dividing
The best time for planting or dividing irises is late August or early September. Division should be made in clumps of three fans to produce blooms the following year.
The fibrous roots should be trimmed to 6″ and spread out. Plant the corms in a sunny location 2″ below the soil surface; the white or stained base of the plant will indicate the proper depth.
Because Japanese irises grow vigorously, allow 24″ between the plants. Then, saturate the soil thoroughly and keep the newly set plants well-watered for the next month.
Hardy In Temperate Climates
Japanese irises are hardy in temperate climates, but a winter mulch of oak leaves is beneficial in parts of the country where freezing and thawing are severe.
In spring, the plants should be well watered and fed with liquid manure when coming into bloom.
During the latter part of summer, they can withstand fairly dry conditions. As a result, they are seldom troubled by any pests.
Varieties In Two Classes
Varieties generally fall into two classes—doubles and singles.
The singles are more graceful, with three short, upright standards and six falls. In the doubles, all six petals are large and spreading; they may droop or be ruffled, but the effect is striking.
The spectacular fluorescence is caused by the horizontal petals and reed-like, almost vertical leaves.
Colors range from white, blue, purple, and lavender to maroon. The blooming period runs from late June through July.
Catalog listings are not as confusing as they used to be.
Among the favorites are:
- Light in the Opal, double, orchid pink;
- Betty F. Holmes, double, pure white;
- Summer Storm, deep purple
- La Favorite, double, white-veined purple
44659 by Elizabeth J. Marshall