The "secret" to growing any type of iris is to find out what works for others who have the same growing conditions and emulate their practices. There are excellent resource books available including THE WORLD OF IRIS, MAGIC OF IRISES by Barbara Perry Lawton, and THE GARDENER’S IRIS BOOK by Bill Shears. Only basic starter tips are provided here.

For Aril and Aril-bred Iris, Sharon McAllister is an excellent source of information.  The irises that fall within the horticultural classes of aril and arilbred irises are so very different from each other and so variable that there must be some understanding of the entire collective group in order to grasp the particulars.

The Aril iris include five (5) groupings, with the two major groups being Oncocyclus and Regelia Irises. The Oncocyclus are true desert dwellers, found in the mountain ranges of Turkey, Iran, and the Caucasus or in the deserts of the Middle East and Asia Minor. The Regelia are more tolerant of moisture than the Oncocyclus Iris. The Regelia are not as well adapted to the desert and may be found in mountain valleys in southwest and central Asia. The word "arilbred" refers to hybrids from crosses between the Tall Bearded iris with the Oncocyclus or the Regelia iris.

It has been suggested to treat Aril Bred Iris (ABs) the same as Tall Bearded Iris (TBs) with perhaps some better drainage. ABs are more susceptible to leaf spot and rhizome rot than TBs. Beginners may want to experiment with growing ¼ breds and ½ breds before tackling the ¾ breds and the pure arils. Another wise choice is to choose varieties that have proven to be good growers.

When to Plant:  The best time for planting arilbred irises is during the dormancy period. The exact time of the year will depend on the climate. Planting during summer heat is stressful, and planting too late in the fall prior to severe winter weather is stressful. It is best to plant as summer fades into the cooler days of autumn, when the plant starts to break dormancy.

Where to Plant:  Aril and arilbreds are more difficult to grow in parts of the United States where the summers are moist. They are more easily grown in warm, dry regions of the country, especially in desert-like areas such as Arizona and New Mexico. Raised beds or sloped beds may be advantageous provided these offer good drainage. Select an area with plenty of sunshine and good drainage. In the desert and high altitude areas where the sunshine is intense, afternoon shade is suggested.

Soil Preparation:  Good Drainage is essential to growing arils and arilbred iris. If the soil is acid or neutral, add limestone to increase the pH. Arils and arilbreds prefer a more alkaline soil than do bearded iris. The alkaline soil needs to contain a good amount of calcium and magnesium, which can be obtained by using slaked lime or ground limestone. Dolomitic limestone, which contains magnesium, is especially good. The soil must be highly fertile and rich in mineral nutrients. Organic matter, such as well-prepared compost, is beneficial.

Distance Apart:  Giving them more space for circulation is suggested. These iris resent crowding.

Watering: If summers tend to be dry in your region, stop watering and allow the plants to go dormant during the hot dry months. Begin withholding water right after the blooming season. If summers are excessively wet, arils can be protected from excessive water using overhead awnings or canopies. The key to growing is providing good drainage.

Fertilizing:  Arilbreds are heavy feeders and benefit from regular fertilizing. Feeding with soluble fertilizer having high potash and phosphate rating may be useful.

Bloom Season:  Arilbred iris bloom with the Standard Dwarf and Intermediate Bearded iris.

Moving & Thinning:  Many of the arils and arilbreds increase rapidly and require dividing annually or every other year to avoid overcrowding. Again, thin and replant when summer days begin to cool and before winter days begin.

Pests & Diseases:  Arils and arilbreds are subject to the same array of diseases and pests as Tall Bearded Iris – including attacks by aphids, whitefly, iris borers and other insects, and by leaf spot, rhizome rot and other fungi, bacteria and virus.

Spuria are beardless iris, originating from the Mediterranean 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.

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.

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. Heavier 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. Watering 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.

Watering:  Water regularly from October through the bloom season until about July 1^st. However do not let them sit in pools of water. During the hot summer, spuria can be allowed to go dormant by withholding water. If spuria do go dormant, be sure NOT to water as this will cause rot. Too much moisture combined with summer heat causes rot that damages the new growth.

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. The species I. carthalinae will remain green all summer long – it will not go dormant.

Fertilizing:  Spuria are very heavy feeders. Incorporating plenty of barnyard 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:  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.

The only serious disease is mustard seed fungus or crown rot. Soaking rhizomes in a 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. 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 affected with fungus, so use Terrachlor as a routine measure to prevent instead of treat for mustard seed fungus.

Moving & 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.

Siberian irises are among the easiest of all types of iris to raise. They are also the most adaptable irises for the perennial border and for landscaping. Their foliage is attractive all year, even after the first frost when it turns rusty red-brown. Siberian irises are primarily found in Central Europe and Asia.

When to Plant:  Best time to plant Siberians is in September. Plant immediately after receiving the rhizomes.

Where to Plant:  Siberians are adaptable and hardy. They love full sun but will grow in light shade. In areas of extreme sun and heat, it is suggested that Siberians have some afternoon shade protection. Plant where they will receive at least three hours, preferable six hours of full sun daily. Because watering is similar to other garden perennials, plant Siberian iris with daylilies or similar plants.

Soil Preparation:  Siberians prefer a rich acid soil with lots of organic matter, although they will grow almost anywhere. Soil pH needs to be mildly acidic pH (6.5-7.0). If the soil is over 7.5 pH, work in sulfur, or acidic organic material such as pine needles or peat to help increase acidity. In areas where the groundwater is alkaline, repeated acidification will be necessary.

An organic mulch will benefit the plants in summer by retaining moisture and cooling of the soil. A mulch in the winter can help prevent heaving and thawing problems.

Basic Planting Steps:  Siberian rhizomes will arrive moist, wrapped in paper toweling, cloaked with plastic, and rubber banded to keep them moist until planting time. Two or four fan divisions are recommended for planting and the roots must be kept moist. Plant the rhizomes one inch deep (slightly deeper in sandy soil). Plant 15" to 18" apart.

Watering:  Siberians like lots of moisture in the spring and can survive dry periods in late summer months, but clumps will be healthier if kept moist all summer. Siberians do best if given a minimum of one inch of water per week during the growing season. They can tolerate drought. Too much water is one of the Siberian’s worst enemies.

Fertilizing:  An application of fertilizer higher in nitrogen in the Spring, and a second application of a balanced fertilizer (10-10-10) or (14-14-14) at the end of the bloom season. Foliar feedings monthly with a soluble fertilizer such as Miracid is suggested.

Bloom Season:  Siberians normally bloom at the end of the tall bearded season, 24-34 inches tall.

General Garden Care:  In the late fall cut the foliage back to the ground. After bloom, remove the bloom stalks or the blossom heads to prevent seeds from forming.

Siberian are more resistant to disease than most other garden irises. They may get iris borer that can be treated with Cygon 2E in the spring. Other than the borer, Siberians are almost disease free.

Moving & Thinning:  Some literature suggests digging and dividing right after bloom. Other literature suggests early fall (September) as the best time to thin clumps. Transplants must be kept moist during the thinning process.

Literature suggests dividing Siberian iris after 4 or 5 years if increasing the number of clumps is desired. Otherwise, clumps can grow undisturbed for several years, dividing only with overcrowding conditions, when vigor declines, or when blooms get smaller.

When to Plant:  Japanese iris can be planted and transplanted almost anytime from spring until fall if the transplants are kept wet for the rest of the year and the temperatures are below 90 degrees F for a month afterwards. For regions with hot and dryer summers, the fall will be a better planting time.

Where to Plant:  Japanese iris need six hours of full sun to bloom properly. In the hottest areas, afternoon shade is suggested.

Soil Preparation:  Japanese iris prefers a rich soil with ample organic matter to help in water retention as well as adding nutrients. The soil pH should be slightly acid (5.0 – 6.5). Attention must be given to the pH of your water, which can gradually raise the pH of your soil. An indication of too high pH is the gradual yellowing of the leaves. The addition of granular ferrous sulfate (iron sulfate) or agricultural sulfur can lower the soil pH.

The preparation of your iris bed with compost or manure will be a good start for the JI bed, but do not use granular fertilizer until the plants are established. Leaves, pine needles, grass clippings, straw or sawdust are all good soil amendments.

Basic Planting Steps:  Plant the divisions 12-18 inches apart. Plant the rhizome 2-3 inches deep. They can be planted in a depression that will help catch and hold more water; fill the depression with mulch.  Heavy mulching (2-3 inches) is recommended year round.

Quality of water (pH and / or salts) is the greatest influence upon the Japanese Iris plant. A lack of moisture will stunt the plants and produce miniature blooms. An abundance of water and manure can produce four to five foot tall bloom stalks. JI must be kept watered all summer long. Never let the soil dry out. Mulch the plantings. Depending on the soil, 1-2 inches of water per week is recommended. Older clumps need more water than new divisions. They do very well beside a stream or pond.

Japanese irises are NOT bog plants in northern zones (zones 3-6). One of the biggest misconceptions about Japanese Iris come from seeing photos of flooded fields in Japan. The Japanese flood the fields at bloom time for the esthetic setting and the beauty of the blooms reflected in the water. When JI are planted in a bog and if the water freezes over the top of the crowns the plants may suffocate and die.

Artificial, plastic lined bogs have produced mixed results. If using plastic lined bogs, it is best to put some holes in the bottom and allow the water drainage to be retarded, but not prevented. If JI are grown in pots in ponds, the pots need to be lifted after frost, foliage cut off and the pots buried in the garden. These pots can be returned to the pond the next spring.

Fertilizing:  Japanese iris are heavy feeders and fertilizing three times a year is suggested. A liberal application of fertilizer in the spring and just before or after bloom is beneficial. A third application in the fall is also beneficial. JI like nitrogen. Water-soluble acid fertilizer, such as Miracid (acid type that is used for azaleas and camellias) is good for quick action but only lasts for 2-3 weeks. An all purpose fertilizer such as 5-10-10 can be used and the acid condition provided by the addition of soil sulfur, aluminum sulfate or small pieces of aluminum foil buried just under the soil surface. One half of one pound of soil sulfur per 100 square feet of planting area applied yearly in early fall is ample. Oak leaves, pine needles and peat moss help to supply the acid condition these plants favor, and the more leaves which are used, the less sulfur is required.

Do not let the plants dry out after fertilizing because this will quickly burn the plant roots.

Bloom Season:  Successfully growing JI requires a lot of patience. Under the best of conditions, spectacular display is not attained until the second or third year. JI will bloom shortly after the Tall Bearded Iris.

General Garden Care:  Remove the old foliage after the first frosts. Destroy the old foliage that may contain borer eggs or foliage thrips. The two main pests of JI can be controlled, where warranted with systemic insecticide such as Cygon 2E or Isotox.

Moving & Thinning:  Try not to replant Japanese Iris back in the same soil where JI have grown for three or more years. New roots form above the old roots each year, by the time the crown grow to the surface and the roots can be seen, it is time to dig and divide the plant. Plants under good culture require division every 3-4 years. When bloom sizes and plant height decrease, it is time to divide.

When dividing, cut back ¾ of the foliage and plant 2-4 fan divisions. Keep the transplants well watered until they are well established. Do NOT let the rhizomes or the roots dry out during transplanting – soak in a bucket of water up to 48 hours.