Culture Recommendations
Siberian, Japanese, Pseudatas, and most other beardless irises all require similar conditions. Japanese irises, however, may require a little extra water. These irises grow in ordinary garden conditions or in the perennial border. They all require ample moisture, especially when they are transplanted. Good culture will increase height, branching, flower size, and quantity of bloom. These irises will grow and bloom better if planted in full sun. The table and notes below may be helpful in choosing the right match of beardless irises with your conditions.

Grows in
I. versicolorfull sunmoderateyesheavy5.0 to 6.6
Louisianasfull sun
5.0 to 6.4
Japanesefull sun
heavyyesheavy5.0 to 6.4
Pseudatasfull sunmoderateyesheavy5.0 to 6.0
I. pseudacorusfull sunmoderateyesheavy5.0 to 6.0
Siberiansfull sun
moderatenomoderate5.2 to 6.8
I. gramineasun to
part shade
moderatenomoderate5.6 to 7.0
I. tectorumpart shademoderatenomoderate5.6 to 6.6
Bearded Irisesfull sunlownolight6.4 to 7.4

Soil Requirements: Beardless irises prefer a rich soil with ample organic matter. If the soil is clay, the addition of organic matter will help to loosen it. If the soil is more sandy, the organic matter will help in water retention as well as adding nutrients. Depending on what is available, till in ample amounts of manure, hay, straw, peat moss, etc. If using hay or straw you may need to add high nitrogen fertilizer to compensate for the nitrogen tied up in the decomposition process. If your pH is too high it can be lowered by the addition of granular ferrous sulfate, aluminum sulfate, or agricultural sulfur.

Planting: Plant strong divisions of at least 2 to 3 fans. Small divisions take longer to get started and are more subject to loss. The roots should at no time be allowed to dry out during transplanting. Planting in a small depression (1-3 inches below the average soil level) will help the plant receive extra water during rains. In northern areas, avoid planting in areas where prolonged cover of ice may smother the plants. After planting keep well watered until the plant is established and new growth begins to appear.

Watering: Although some beardless irises are drought-tolerant, many, especially in areas with hot dry summers, benefit from regular watering; some growers have found soaker hoses helpful. Plants that are irrigated become dependent on irrigation and will require it if transplanted.

Mulching: After planting, a heavy mulch helps to conserve moisture as well as reduce weeds. If plants are set out in the fall a mulch is needed to prevent heaving over winter.

Transplanting: Plants should be divided every three or four years or when overcrowded and amount of bloom is reduced. Japanese irises should be transplanted to a new area and not put back into the same ground where they were previously grown. Beardless irises can be transplanted almost anytime from spring until fall, but shortly after bloom period or fall is probably the best. New roots should have sufficient time to anchor the plant before winter freezes. Plants moved or divided in the summer must have plenty of water and some light shade in hotter climates.

Fertilizing: Beardless irises are heavy feeders. .A liberal application of a balanced fertilizer, such as 10-10-10, in spring and just after bloom is beneficial. Foliar feeding with such things as “Miracid” will help weak plants to grow better. Do not fertilize if planting in late fall. This forces growth in warm spells during the winter.

Controlling Pests: Iris borers found in some parts of the country will sometimes attack beardless irises but prefer to dine on bearded types. Check with local growers for newer methods of control. Thrips may also be a slight problem on Japanese irises and may be controlled with a variety of insecticides.

Grooming: Dead foliage should be removed in early winter or early spring. Bloomstalks should be removed after the last flower has faded to keep plants from making unwanted seed.

Members of your local iris club are also a good source of information. In addition, we highly recommend visiting or joining the societies that are devoted to these irises: