Spuria Iris Culture
Ramona Howard
If you grow tall bearded or bearded varieties successfully, you can grow Spurias. They are not as difficult to grow as some other beardless species and cultivars.
They prefer a neutral to slightly alkaline soil. Spurias must have good drainage and prefer full sun, but will tolerate partial shade, especially in areas that have extremely high temperatures in the summer. Most of the garden hybrids have a late summer-dormant period and a drying off period during July through August, which is beneficial. Too much moisture combined with summer heat causes a rot that takes the new growth in both the summer-dormant types and the summer-green types also. In some very dry areas you may need to water through July, but hold back on the water during August, and it should be withheld in established clumps until fall growth begins. Foliage of the summer-dormant types can be cut back to the ground for garden neatness after the foliage dies down about the first of August without harming the plant growth. This can be clipped and removed when completely dried.
Spurias are very heavy feeders and will reward you with superior plants and flower stalks if you incorporate plenty of barnyard manure and/or commercial fertilizer into your soil. If fertilized annually, clumps will persist and bloom for years--10 to 15 year clumps are not unusual, and eventually spread to as much as 5-6 feet.
It is best to transplant in the fall and water well until they start to grow. Once established, Spurias are drought resistant. Heavy irrigation in the spring increases growth and bloom. When Spurias are dug to be transplanted, be sure to keep the roots and rhizomes moist. This is most important, as they will not tolerate drying out, or being out of the ground as some bearded types will.
Planting depth depends on type of soil. If you have heavy soil, you will need to plant at least one inch deep and in light sandy soils plant two or more inches deep. Space them far enough apart to grow in the same location for several years as Spuria irises are very temperamental in that they resent being transplanted and usually do not bloom the first year after planting. The second year you will be rewarded with several bloom stalks. Although the fall is generally thought to be the best time for transplanting, they may be transplanted at other times if you are careful to not let the roots or rhizomes dry out. Spuria iris clumps may be left in the same location for years, but remember they will need to be well fed so that the quality and quantity of bloom will continue to be good.
Virus affects some Spuria irises and can be worrisome, although it is almost never fatal among the named cultivars and seldom is very debilitating under good cultural conditions. It causes some disfigurement of the plant, petals and texture. There is no known cure, but resistance must be bred into the Spuria plant by using virus-resistant parents and making careful selections of seedlings for future breeding. The only serious disease is mustard seed fungus or crown rot which also affect Louisiana and bearded irises and daylilies. Soaking rhizomes in 5% sodium hypochlorite solution and thoroughly mixing Terrachlor into the soil before planting are effective controls. Also dust or spray annually in the summer for prevention as it is much easier to prevent than get rid of, once your irises are affected. The mosaic caused by one type of virus has symptoms of a light green and gold streaking and mottling of leaves. In some varieties the plant may be stunted, but hopefully a variety that is so susceptible would not be put on the market. Evidence of the mosaic infection may be striping in the foliage, dark flecking or watermarks in the flowers and distortion of petals.
Why not try some of the inexpensive varieties of Spuria irises to start with and do remember to plant them where they will get lots of sun and have good drainage. It really is easy as growing bearded irises. It might take a little more food and water, but the results will be worth it. They make excellent cut flowers and last well in flower arrangements, so your efforts will be well rewarded.
(Reprinted from SSIS Newsletter, June-July 1989)
Cultivars Suggested by the Spuria Iris Society
Golden Lady, Elixir, Dawn Candle, Baritone, Highline Lavender, Port of Call, Archie Owen, Marilyn Holloway, Imperial Bronze, Forty Carats, Proverb, Clark Cosgrove, Ila Crawford, Buttered Chocolate, Imperial Ruby, Fergy's Poetry, Highline Honey, Adobe Sunset, Imperial Gold, Betty Cooper, Son of Sun