Spuria culture

growing spuria irises successfully

(parts by Floyd Wickenkamp from the Spuria Iris Society Newsletter, Summer 1999)

When to Plant: 
Spuria are dug in the fall before they start showing signs of new growth. Rhizomes must be washed well and placed damp in a plastic bag for storage in the refrigerator, NOT in the freezer. Plant as soon as possible. (NOTE: author of this web site has had no experience using the refrigerator and this is not really necesary)

Where to Plant:
Spuria thrive in full sun best, but will do well on half a day's sun throughout the year. They will tolerate partial shade, especially in areas that have extremely high temperatures in the summer.

Soil Preparation:
Spuria prefer a neutral to slightly alkaline soil and they must have good drainage. Enrich soil by adding alfalfa and manure. Heavy clay soil is much better than fine sandy soil.

Basic Planting Steps: 
Some spuria are difficult to establish. Basically spuria need water, manure, and mulch to become established. Begin the planting by making sure the soil will allow for good drainage and is enriched. Then make a hole about two inches below the surface. Add fertilizer (14-14-14 is suggested) to this hole. Then put lots of water into this hole. Finally add the rhizome, cover with soil and mulch. Wateriing this new spuria rhizome from the top of the soil is not sufficient for establishing a clump. Mulch spuria the first year of growth. Saw dust is the best mulch to use. After the clump is established the mulch may be removed during the blooming season. 

Distance Apart:
Space spuria far enough apart to grow in the same location for years as Spuria irises resent being transplanted. Spacing spuria rhizomes three feet apart is suggested. 
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Water regularly from October through the bloom season until about July 1st. However do not let them sit in pools of water. During the hot summer, spuria can be allowed to go dormant by witholding water. Too much moisture combined with summer heat causes rot that damages the new growth. (See virus and fungus below)

Spuria are very heavy feeders. Incorporating plenty of barnyard manure (or commercial composted manure) and/or commercial fertilizer into the soil is advisable. Ordinary lawn fertilizer (10-10-10) works well to feed the spuria in the spring and again in the fall.

Bloom Season:
Spuria usually do not bloom the first year after planting. The second year should produce several bloom stalks. The bloom time is one to two weeks after the tall bearded irises. 

General Garden Care:
(Note: The spuria may die all the way back in the summer the first year. They will return in the fall when new growth begins. The species I. carthalinae will remain green all summer long -- it will not go dormant.) 

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. Spuria seem to set seed easily and are somewhat easy to grow from seed. Bees are more attracted to spuria than other iris; thus pollination and seed production is more prominent with spuria. 

Moving and Thinning:
Although the fall is generally thought to be the best time for transplanting, they may be transplanted at other times if you are careful not to let the roots or rhizomes dry out. Storing spuria rhizomes in the refrigerator before replanting may trigger faster growth and earlier bloom. Dip the mature rhizome in a fungicide and store them in plastic bags in the refrigerator for several weeks to get this response. 

(The web author has no experience with early digging and refrigerator storage.) If the rhizome is dug early and allowed to dry out, be sure to soak the rhizome in a pail of water for about 1 to 2 days before planting.

Virus and Fungus:
Virus affects some Spuria irises, although it is seldom very debilitating under good cultural conditions. It can cause stunting or striping of the plant and petals.

Too much watering combined with summer heat causes mustard seed fungus growth -- and watering intermittantly -- once you stop watering, do not start watering again in the summer months -- just allow the spuria iris to go dormant.

The only serious disease is mustard seed fungus or crown rot. Soaking rhizomes in a 5% sodium hypochlorite solution and thorougly mixing Terrachor into the soil before planting are effective controls. Also, dust or spray annually in the summer for prevention. It is much easier to prevent the mustard seed fungus than to get rid of it once the iris is affected. Watering spuria in August is an easy way for spuria to become infected with fungus, so use Terrachlor as a routine measure to prevent instead of treat for mustard seed fungus.


spuria culture continued...

Additional Information


The above photos were taken in SW Kansas. The rhizomes from Photo Two (in bag) were planted in the Fall of 1999. There were fertilized and watered. In the Spring 2000, the foliage grew well. There were no flowers in Year 2000. In Summer, the foliage died all the way to the ground and I thought the iris had died, but in the Fall of 2000, they all began to grow back again. There was bloom the second year, but the stalks were shorter than expected. Year three, the stalks are usually at expected height.

More About Manure: 
(The following text is from the Summer 2000 Spuria Newsletter, used by permission -- author unknown)
If you can grow bearded irises, you can grow spurias. If a few care guidelines are followed, spuria will reward you with beautiful garden bloom and long lasting cut flowers.

Spurias prefer the same soil as tall bearded iris and they must hve good drainage. They prefer full sun and will bloom better if they are not under trees or shrubs, even in extremely high temperature areas in the summer. Most of the garden hybrids have a late-summer dormant period. In extreme heat areas, it is best to withdraw water by the 1st of June and let them go totally domant. If they go dormant, do not water them. In established clumps, water should be withheld until fall growth begins. Foliage of the dormant types must be cut back to the ground, not only for neatness, but to allow air to reach the rhizomes. 

Spurias are very heavy feeders and will reward you with superior plants and flower stalks. Some growers swear by manure, but in hot desert areas, do not use manure. It will cause rot and other fungus. Manure is high in nitrogen and that will produce the green growth, but not the desired bloom we are trying to get. Use a fertilizer high in phosphate to bring out the bloom. It can be used every two weeks after frost and before bloom starts. If watered and fertilized properly, clumps will persist and bloom for years. It is not unusual to see older clumps spread to 5 or 6 feet in just 5 to 6 years.

Some say it is best to transplant in the fall when new growth is beginning, but others have found digging while dormant does not produce the shock treatment of transplant. Dormant rhizomes will start growing roots and showing new growth within 10 days. In cold climates, their growth gets started and established for the winter if they are planted in July or August. In hot desert climates, plant in October. Be sure to water well when first planted. In the spring, water well to push bloom. During dormancy, do not water at all. Once established, spurias are drought resistant.

When spurias are dug to be transplanted, be sure the roots and rhizomes are moist. This is very important, as they will not tolerate drying out when out of the ground for long. They can be packaged with a wet towel or newspaper and placed in a plastic bag. (Note: the article author says they can be stored in the refrigerator for as long as 3 to 4 months. In fact, this long refrigeration will enhance an early bloom in the spring the first year. Note: the web author has no experience with refrigeration). Planting depth depends on type of soil. If you have heavy clay you will need to plant at least one inch deep and in light sandy soils plant two inches deep. Space them far enough apart to grow in the same location for years as spuria irises resent being transplanted and will usually not bloom the first year after planting. The second year you will be rewarded with several bloom stalks.

History of Spuria Iris:
Spuria are beardless iris, originating from the Meditterranean area of Europe. They are also seen in lesser numbers in England, Denmark, Russia, Afghanistan, and western China. Spuria iris are one of the tallest of iris, reaching a height of 5 feet or more. Experience has shown that spuria iris perform better in areas of the country where the summer months are dry.

Spuria irises are classified under the Apogon or beardless subsection of the iris family. The twenty or more species are native to the temperate zone in the band running from Spain and North Africa to India and China. The greatest collection of the species has been found in southern Siberia, always in sunny locations.

The largest concentration of activity in growing and hybridizing spurias is in the sunnier and warmer parts of the U.S., especially California and the Southwest, including Texas and Missouri, and in eastern Australia, but they have also been grown successfully in Montana, Minnesota and Oregon as well as in northern Europe.