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Cultural and Classification Information (updated March 25 2009)
Cultural Information Cultural Information: Planting and Growing Iris by Betty Wood
To plant your irises, choose a sunny spot in well drained soil. Prepare the soil well, by spading or turning over the soil with a garden fork to a depth of at least 10 inches. Spread fertilizer and work it into the top of the soil. If possible, this should be done 2 to 3 weeks before you are ready to plant. A well prepared bed will result in better growth and more bloom. Don't starve your irises or make them compete with nearby grass or weeds for food and water. Many gardeners, iris and otherwise, have soil analyses made of their garden soil, then add the fertilizer of the kind and quantity the tests show the soil needs. The soil should be light. If it is clay soil, add very coarse sand and humus. Bone meal and a good garden fertilizer, low in nitrogen, are good for irises, but manure should be used only after it has aged for about a year. Otherwise, it may cause rot. The roots must be buried firmly to hold the plant in place, but the rhizome should be near the surface. An easy way to achieve this is to dig two trenches with a ridge between them, place the rhizome on the ridge and spread the roots carefully in the trenches. Be sure to firm the soil tightly and allow enough for settling to keep the rhizome above any possible standing water. Then fill the trenches with soil, letting the top surface of the rhizome be just barely beneath the surface of the soil. If you have several plants, plant them at least a foot and a half apart, "facing" the same way. The rhizomes will then increase in the same direction, without crowding each other too soon. From the new parts of the rhizome, new bloom stalks will come up in later years and the flowers will be exactly as the original flower. This is called "vegetative propagation". In about 2 or 3 years, the new rhizomes will begin to crowd each other and you will want to divide the plant, cutting the newer parts of the rhizome free from the old, which may then be discarded. Unlike the other bearded irises, arils need to be transplanted annually. You will have so many new rhizomes that you will share them with your friends. Perhaps you received your first rhizomes from a friend. When digging, keep all plants carefully labeled with their names, for sure identification. It is wise to keep diagrams of your planting area to double check individual labels on the plants. This digging and separating is best done between one and two months after bloom season, usually in July or August. Soon after this the irises grow roots which help to hold the plant firmly during the winter in areas where freezing and thawing can result in heaving the rhizome out of the ground. If you live in this type of climate, a mulch of salt hay can be very beneficial. Culture of the beardless irises differs somewhat from culture of the bearded irises. They should be transplanted in the fall or in early spring. The roots should never be allowed to dry out while they are out of the ground and they should be watered heavily after transplanting. They should be set slightly deeper than the tall bearded. Japanese iris should be planted in a distinct "depression" in heavy soil to assist in supplying moisture to the plant. Siberians and the Pacific Coast Natives can tolerate light shade but the Spurias, Japanese and Louisianas demand full sun. Louisianas and Japanese require moist conditions during the summer months while the Pacific Coast Natives enjoy a very low humidity and dry soil no matter how hot it may get. All, except Louisianas, should be planted in a permanent spot where they can remain for many years as they resent being disturbed. Louisianas tend to "creep" and therefore, should be tended to every few years. All are heavy feeders and need to be fertilized regularly. The irises most often used
as garden plants fall into three main groups: Bearded IrisesBearded Iris are identified by thick, bushy "beards" on each of the falls (lower petals) of the blossoms. Originally, most of these were native to central and southern Europe. The American Iris Society has divided the bearded irises into six groups for garden judging awards. 1. Miniature Dwarf Bearded (MDB) -- the tiniest of bearded irises, with height of up to 20 cm (8 inches). They are also the earliest to bloom. They are most effective in rock gardens or planted in drifts where they make a "carpet of color." 2. Standard Dwarf Bearded (SDB) -- some of the most useful garden plants, ranging in height from 20 cm (8 inches) to 41 cm (16 inches). They begin their bloom as the MDBs are ending, still quite early in the iris season. They are best displayed in clumps where they give the effect of a "cushion" of individual blooms. The colors are nearly unlimited since the SDBs show all the different "spot patterns" of the miniatures, as well as the plicatas and pinks seen in the TBs. 3. Intermediate Bearded (IB) -- stand from 41 cm (16 inches) to 70 cm (27 1/2 inches) high, with their bloom season overlapping the SBDs and the TBs. Although the IBs show their dwarf ancestry in early bloom season and very interesting color patterns, they are large enough that their individual stalks may be nicely branched, forming an elegant bouquet. Some varieties are nicest in clumps, where they present a large amount of color (like the SDBs), while others are showiest in specimen plantings, where the stalks and individual blooms may be seen to best advantage. 4. Border Bearded (BB) -- essentially small versions of the TBs in the same height range and bloom size as the intermediates, but blooming with the tall beardeds. Good BBs have round, ruffled petals that complement their small size. 5. Miniature Tall Bearded (MTB) -- this class is distinguished by daintiness and delicacy. Height from 41 cm (16 inches) to 70 cm (27 1/2 inches). The blooms are smaller than on a BB and the stems are thin and wiry. An MTB clump looks like a cloud of butterflies. They are often called "Table Irises" because they are so well suited for arrangements. 6. Tall Bearded (TB) -- have stalks with a height of 70 cm (27 1/2 inches) and above, with branching and many buds. Each stalk, in itself, makes a stately arrangement in the garden or in a vase. In addition to a wide variety of colors and patterns, the TBs display other qualities (such as ruffling and lacing) more frequently than do the other classes Even if you grow nothing but bearded irises, you can enjoy a remarkable range of color and a bloom season extending for months. Some bearded irises are "rebloomers", blooming again in the summer, fall or winter. Additional water and fertilizer applied during the summer months encourages them to bloom again. There are now reliable attractive rebloomers available which will perform in all but the coldest climates. Incidentally, the word "median" refers to all the bearded irises except the miniature dwarfs and the tall beardeds; that is to say the SDBs, IBs, BBs and the MTBs. Strictly speaking, the word "dwarf" means only the MDBs. Aril IrisesTwo very different types of irises are grouped together under the term "aril". These are the oncocyclus and regelia irises of the Near East. Although they have beards, they are not classified with the bearded irises because they are so different. Actually, their beards are rather sparse, being long and straggly on the regelias, and nothing more than a wide "fuzzy" patch on the oncocyclus. The arils show dark signal spots below the beards with much veining and speckling, in an unbelievable range of colors. Unfortunately, the arils are difficult to grow in all but the warmest and driest regions of the United States. However, in this century, hybrids were produced from crossing the arils with the more common bearded irises. These are called "arilbreds" (AB), and are usually very easy to grow and still display the spectacular features of the arils. Most arilbreds are tall and have large blooms. They usually bloom earlier than the TBs, with the SDBs and the IBs. There are also small arilbreds, produced from crossing arils or arilbreds with dwarfs or medians. They are variously called "arilbred-medians", "aril-medians" or "aril-meds". Beardless IrisesBeardless Irises are mostly native to Asia. The first four types are commonly grown in gardens, and they all bloom after the TBs, extending the iris season even longer. The fifth type, the Pacific Coast Native, blooms before the TBs and is native to the western regions of the United States. 1. Spurias (SPU) are tall (2 to 5 feet in height) and elegant, and have very attractive foliage. The shape of the bloom often suggests orchids and the colors range from white and yellow through blue, wine and brown, often with bright yellow signals. 2. Siberians (SIB) perform best with cooler conditions, regular moisture and a slightly acid soil. The blooms can be blue, purple, red-violet or yellow with newer cultivars in brown and orange shades, and can have a variety of forms from upright to flat and round. They are most attractive in established clumps that develop a bouquet effect and grow to a height of 2 to 4 feet., although some dwarf varieties are also available. Their grass-like foliage after bloom is one of their attractive garden features. They tend to bloom slightly later than the TBs. 3. Japanese (JI) require a slightly acid soil and present some of the most spectacular flowers of all the irises. Blooms are usually huge, ruffled and flat in form; some are marbled with gray or white. They bloom about a month after the TBs. Japanese hybridizers have worked with them for over 500 years. 4. Louisianas (LA) are native to the American Gulf Coast; they require soil that is somewhat acid and wet in the spring. The blooms are usually very wide petaled and open, showing brightly colored style-arms and sharp signal-crests. 5. Pacific Coast Natives (PCN), or Californicae (CA), are not widely grown as they are intolerant of the climatic conditions of all but the far western area of the country. Where they can become established, they grow most attractively with graceful and dainty flowers held one to two feet high, in most colors and patterns. 6. Species often enhance gardens with their delicate beauty. I. confusa (Evansia) requires conditions similar to azaleas in a frost free climate. I. missouriensis enjoys wet springs and dry summers. Contemporary Views by Perry Dyer:
A collection of Contemporary Views by Perry Dyer of Oklahoma from 1988 to 2008. These are annual articles involving personal observations and commentary on current varieties of irises. Contemporary Views Compendium 1998-2008 (all articles below in one file) (PDF 2.2 MB)
Contemporary Views 1988
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Irises are among the easiest
of perennials to grow, and they give an abundance of beauty with minimum
care. The iris has a thick fleshy root called a "rhizome"
(pronounced rye-zome) about like a tough potato in texture. When you buy
a new iris, you will probably receive a rhizome with clipped roots and
leaves. It can remain out of the ground for a week or two without
serious harm, but the sooner it is planted, the better.
photo by Tom Gormley