Bearded Irises

Bearded irises are the irises of your grandmother's garden, the ones that have been called German irises or flags. It was Carolus Linnaeus, the eighteenth century Swedish botanist, who assigned the binomial scientific name Iris germanica to the tall bearded irises. Linnaeus published Species Plantarum, his tome on botanical taxonomy, in 1753. This spelled out the system of binomial nomenclature that we use today. But Linnaeus erred on Iris germanica, the sample of which may have been sent from a German garden. The plant does not grow wild in Germany and, in fact, Iris x germanica is not a species but rather is probably a natural hybrid of intermediate height.

All of the ancestors of the bearded irises came from central, southern and eastern Europe and the Near East. Bearded irises have played the starring role of the family Iridaceae for so long that detailed origins of this favorite perennial are shrouded with the mists of time. Quite probably, many of the iris species crosses took place naturally because of the proximity of the plants, and it's possible that early plantsmen were breeding irises many centuries ago. It is quite likely that early iris breeding was the process of selecting desirable irises from crosses made by bees rather than the modern human-made pollinations.

Most taxonomic botanists believe that modern bearded irises are the result of interbreeding among about fourteen wild iris species, including albertii, cypriana, gatesii, kashmiriana, mesopotamica, pallida, trojana and variegata. Since the variations in size increased with these breedings, the bearded irises have been split into six different groups, based on plant size and growth habit.

Plant characteristics

Bearded irises are stately plants. Tall or small they produce flowers of elegant form. They grow from a rhizome with fans of sculptured, sword-shaped, bluish green leaves standing stiffly upright or curving gracefully at their tips. In some varieties the leaves have a surprising and attractive purplish red tinge at the base. The waxy coated leaves express the overall well-being of the plant, with healthy leaves having a bluish tinge and growing vigorously from the middle of each fan.

The rhizome, or swollen stem, is where the plant stores nutrients and moisture, enabling it to survive a certain amount of stress. Spring growth occurs immediately after flowering, usually for about one or two months. During mid-summer the plants take a rest, with further growth occurring again in the fall before the leaves die down and the plant enters a dormant state for winter.

Rhizomes grow along the surface of the soil, sending leaf fans upwards and roots downwards from their growing end. During the heat of summer the rhizomes become hardened, protecting the resources within and making it difficult for pests and diseases to gain entry. However, long periods of wet weather can soften and weaken the rhizome, allowing slugs or other pests a hearty meal.

Rhizomes naturally divide and increase annually, eventually forming a complex interwoven mat. To ensure good flowering each season, the iris should be divided before this stage. Each rhizome will flower only once and then grow new rhizomes behind the current season's flower stem, or sometimes from buds along the rhizome's length. Multiplying in this way gives the plant the opportunity to access further nutrients in newer soil. The fan itself is the leading edge of the growth point and from here the plant marches outwards, away from the spent mother rhizome. Different varieties increase and grow at varying speeds, some producing a large number of increases each year, others comparatively few.

Flower characteristics

As with all irises, the flower consists of three standards, three falls and three style arms. In the bearded irises, the delicately dome-shaped standards usually close over the top of the flower protecting the style arms, which are often beautifully colored. The stigmatic lip or female part of the flower lies on their underside; the pollen-bearing anther, or male part of the flower, hides directly under the stigmatic lip.

Curving outwards and downwards, the falls or lower petals display the beard, an appendage somewhat like a large fuzzy caterpillar, which is the main distinguishing characteristic of this group.

Beards come in many colors, even the same color as the flower, giving an intense overall effect. The heavily ruffled purple-black 'Night Ruler', is a good example. Beards may also be a completely different color as seen in 'Stately Art', where the lovely blue is complemented by a surprisingly red beard.

Beards add character and charm to the flower, enhancing and complementing the colors in the falls. In some hybrids the beards may also have extensions or horns and other interesting appendages such as spoons and flounces. The white iris 'Mesmerizer', with its frilly flounces, has an appearance of a double flower. 'Thornbird', an unusual tan, has remarkable bright violet horns. Irises with these characteristics are known as "Space Age" irises.

Falls may be frilled, smooth or ruffled, broad or narrow, and may stand out like a saucer, fall gently downwards or recurve under the flower.

The flowers of bearded irises, once open, will remain in good condition for about three days, depending on the temperature. It is simple to remove spent flowers as they close. Supporting the base of the new bud firmly, carefully bend the spent flower down and out with a sharp movement. It should snap cleanly away from the socket.

Color patterns vary widely from single to multiple hues that include streaking, thumbprints and veining. There are special names to denote particular patterns. A single color, for example, is known as a "self" and 'Blenheim Royal' is a fine example of a true, rich, purple self.

The flower spike of bearded irises should have at least two branches with both stem and branches producing several flowers. Ideally a good spike will have strong branches curving out from the main stem and supporting the flowers in a balanced and upright manner, not unlike a candelabra. Perfection is three flowers open at once in a balanced form, evenly spaced down the spike.

The dwarf bearded irises are known for their thumbprints of rich contrasting color below the beard, a pattern that is only just beginning to emerge in the bearded irises.

Flowering spike

The choice of a background and foreground for bearded iris is closely related to the height of the flowering spike.

Just as there are desirable traits in plant habit there are also desirable traits in the flower spike:

• Strength - the spike should be strong, able to support the flowers and sufficiently rigid to ensure that it will not be blown over by the wind. A good iris should not need staking in the garden.
• Proportion - the spike should be in proportion to the foliage. It should be tall enough for the flowers to be above the foliage. Further, the branches that make up the spike should be evenly spaced down the spike.
• Presentation - the spikes should be well branched with each branch able to display the blooms gracefully and uncluttered. Each branch should have multiple buds to ensure a long flowering period-a minimum of 3 branches and 6 blooms. Some iris are equally satisfactory if they carry fewer buds to the spike but multiple spikes to the rhizome. An example of the latter is the beautiful light pink iris 'Vanity'. This classic beauty often has only 4 buds to the spike but will at times send up 3 or more spikes from a single rhizome.

The concurrence of open flowers on the various branches of the spike is also important. A flower from each branch may open simultaneously, making a great splash of color and giving an ideal spike for showing. Alternatively, the flowers may open intermittently, giving a longer period of bloom in the garden.

It can be amazing how quickly the flowering spikes emerge from the foliage. A guide, although not foolproof, for telling if a plant is to flower is a noticeable curving of the central leaves in the fan of foliage. The presence of a spike can be confirmed by gently feeling the base of the fan. In the early stages of development the spike can be brittle and care should be taken to avoid knocking the spikes, especially when weeding. It is thus advisable to have your iris clumps weed-free prior to the flowering season.

After reaching full height the rapid change in the appearance of the spike slows down. The flowers now develop in size. The time taken from the emergence of the spike to the start of flowering varies considerably but can be less than two weeks.

Culture of bearded irises

Undoubtedly, one of the major reasons for the centuries-old popularity of the bearded irises is their ability to thrive under a variety of environmental conditions. Although the ideal soil for these irises would be 6.8, nearly neutral, they will grow quite successfully in soils with a pH range of 6.0 to 8.0, from mildly acid to somewhat alkaline. Neutral on the pH scale is 7.0 while anything below that is acid and anything above 7.0 is basic or alkaline.

If your soil is in the acid range with a pH of below 6.0, mix garden lime into the soil at the rate indicated on the container. To raise soil pH from 5.0 to 6.5 will take between 8 and 15 pounds of lime per 100 square feet, depending upon the soil type- less for sandy loam than for clay loam. If your soil is too alkaline with a pH of over 8.0, you can lower it to the desired level by mixing aluminum sulfate, ferrous sulfate or soil sulfur into the soil at a rate of 2 pounds per 100 square feet. Wait two weeks, then test the soil again. Repeat if necessary.

A sunny site and medium fertility are requirements for top bloom production. Make sure that bearded irises get at least a half day of sun. Best performance will be in full sun. In extremely hot climates, some shade late in the day will be beneficial. Bearded irises tend not to thrive in the hot humid southern state of Florida and along the Gulf Coast where warm rainy summers are usual. They tend to do well in the drier regions of the southern states.

Although bearded irises will grow well in a wide variety of soil types, they will perform to the greatest potential in soils that are classed as loam or clay loam. The major cultural requirement for soils in which you wish to grow bearded irises is good drainage. If your soil falls outside of these categories, it will pay to amend it with organic matter. For best results in improving the structure of extremely sandy or clay soil, cultivate 3-4 inches of compost, well-rotted manure or a good quality of peat moss into the soil to a depth of 12 to 15 inches two to three weeks before planting irises.

Avoid planting irises on slopes where rains can pile up silt and soil against iris rhizomes and even cover them. Those rhizomes will be most healthy if they are fully exposed to sun and air. Some experts recommend a light covering of soil in extremely cold climates while others stick with the recommendation to leave the rhizomes exposed to sun and air, no matter how cold the winter weather.

Climates where winter contrasts can range from 20 to 70 degrees F in a single twenty-four-hour period can be tough on irises. There are irises that do not go completely dormant or do not remain dormant during winter months - they can be grown most successfully in regions with mild climates. They probably would be lost in climates with harsh freeze-thaw cycles.  A light mulch of loose straw also will protect bearded irises during snowless winters.

Knowing the growing patterns of bearded irises explains why July and August are the months of choice for planting these irises in cooler climates and through late fall in warmer climates. From early spring until after the flowers appear, the plants' major growth is aboveground. The nutrients stored in the rhizomes are used for the growth of leaves, flower stalks, buds and flowers. Once the bloom period is past, plant growth during the next six to eight weeks concentrates on underground growth, on the development of increase buds that will become new rhizomes and on the development of new flower stalk buds for next years growing season. At the same time, the plants are storing nutrients for next years growth.

At the end of this underground growth period, the bearded irises are mature and, with the exception of the reblooming varieties that continue to grow throughout the warm season, will have a period of semi-dormancy. This is the best time to transplant them, when the rhizome is fully developed and while they are in their late-summer semi-dormant state. Plant at this time and the rhizomes will initiate new root growth in moist soil until hard frost. It is important that the roots of recently planted irises have an opportunity to become well established before the end of the growing season. Allowing the rhizomes to thoroughly dry out for several days or even a week will dry and callus the cut surfaces and diminish the chance of fungal diseases. A light dusting of horticultural sulfur also is a fungal deterrent.

Dig a wide, shallow planting hole with a mound of soil in the middle. Set the rhizome on the mound and spread the roots out around it. Set the rhizomes with the fans facing the outer edge of the bed so that future growth will not result in a crowded mass of rhizomes. Fill with soil, making sure that the rhizome is at the soil surface and just barely exposed. In very light soils and in very hot climates, experts recommend covering the rhizomes with about an inch of soil. Water well, then water regularly if the soil is dry.

General care of garden irises includes thinning or dividing the plants every three to five years, depending on how crowded the plants are. Trim any injured, damaged or diseased foliage but leave the healthy green foliage undisturbed. Keep iris beds free of weeds and debris so that the tops of the rhizomes can bask in the summer sun. After the plants flower, cut or snap the bloom stems off close to the ground. Some irisarians mulch with an inch-thick layer of pine needles to keep down weeds, but be sure that the mulch does not touch or cover the rhizomes.

Division

After two or three years, the older rhizomes at the center of a clump become unproductive. To maintain its vigor, the plant needs to be divided and transplanted. The best time is after flowering, when the fleshy white roots visible under the leaf fan easily identify the growth period. Divided then, the plant will quickly re-establish itself, securing the rhizome firmly in the ground and enabling it to support the next tall flower stem without toppling over.

Transplanting during periods of dormancy, such as in winter, is not a good idea as the plant will have to survive on the stored resources of the rhizome. As the next period of growth is not until after flowering, it is likely that the flower stems will be shorter, and flowers smaller than normal.

To divide an existing clump, first dig up the whole plant using a strong garden fork. Keep only the best new plump rhizomes with fresh, strong, green leaf fans and good root systems. Separate them from the older plant with a clean cut. They should be no shorter than the length of a thumb. Trim the leaves by about one-third. This helps prevent both wind-rock and excessive moisture loss while the new roots establish themselves. Discard the older unproductive rhizomes -they can be composted.

Planting

Plants purchased from an iris nursery will arrive by mail or courier and the roots will be bare. Check the plants for firm rhizomes and dry leaves. Don't panic if the leaves tend to be dry and browning; this is how they ought to be. There should be strong roots, which may have been evenly trimmed, but they should still be at least 4-6 in (10-15 cm) long. Allow free exposure to the air and keep them in a cool, dry place while you prepare the bed.

Plant the rhizome with its top level with the soil surface. Having prepared the soil, dig a hole wide enough to take the young rhizome with outspread roots. Place it in the center of the hole on a raised hump of soil, carefully spreading the roots downwards and away from the rhizome, deep enough to secure the plant firmly. Wind-rock or movement is the worst enemy of newly planted bearded irises as the new roots can be rubbed off as soon as they emerge. Fill in around the plant with the removed soil and press firmly with your foot. Check that the rhizome is level with, or above the natural level of the soil. Water generously after planting and thereafter keep the soil slightly damp for about two weeks. Once the new roots appear, the plant will be able to withstand dry periods.

Hygiene

During the growing season, the rhizome grows along the ground with the fan of leaves and new roots leading the way. New leaves come up in the center of the fan and the older leaves get pushed to the outside, eventually browning, falling and covering the rhizome. In very hot climates these decaying leaves may protect it from sunburn, but beware: in more, temperate climates the spent leaves can provide cover for slugs, snails, slaters and earwigs, as well as host spores of fungal diseases. It is wise to check the plants frequently during the summer, removing all older foliage. Leaves are the source of many nutrients for the plant and to ensure a good season to follow, leave as much foliage as possible during the growing period.

It is essential to keep the clump weed-free and not allow overgrowth by other plants. Bearded irises are not hard to keep clean, so long as you understand their growth habit. Removal of large weeds with tap roots, such as dock or dandelion, can be achieved quite easily by using a sharp spade. A single deep angular plunge beneath the rhizomes (not directly in front of or close to the leaf fans) will cut the tap root of the offending weed. Place your foot firmly on the rhizomes and pull the weed out. It should come easily without the clump suffering any ill effects. Roots tend to be widespread and shallow, and with only one spade cut, very few will be damaged.

Species

The amazing flowers we drool over today are hybrids, developed by years of sometimes planned, sometimes fortuitous hybridization. The different species from which they originated come mainly from Europe and the Mediterranean countries -collected and transported by early travelers -and seldom show any similarity to modern blooms. Yet it is their heritage that accounts for the differences in their growth habits, disease resistance, height and the characteristics of the flower. So many other factors come into play, such as high summer heat, extreme humidity, rainfall and local microclimates.

From southern Europe came Iris pallida of orrisroot fame, characterized by its paper-like flower spathes sheathing the buds and treasured for its glaucous blue-green foliage that stays handsome right through summer. Its flowers are soft mauve-blue, lilac or lavender. There is also a variegated form I. pallida variegata, an excellent garden form with the advantage of variegated leaves to enjoy when the flowers are over for the season. I. pallida added height to the hybrid equation but offered very little in the way of branching genes.

I. mesopotamica

From Armenia and Turkmenistan brought beautiful blue flowers into the bearded irises as well as height and branching attributes, but it is frost tender in colder districts -a less desirable trait passed on to many hybrids that share its genes.

I. variegata

Comes from central Europe and the Balkans, and it is to this plant that we owe all the yellow tones in bearded irises. Those gardeners who like the old hybrid 'Gracchus' would see similarities in its pale yellow standards with white falls striped in red-purple. I. flavescens, also yellow and classed as a species, is probably a cross between I. pallida and I. variegata.

I. germanica

Many bearded iris species are listed under this name but it would appear to have become an umbrella term for a group of early hybrids that have naturalized in many countries and that flower in late winter or early spring, before the bearded irises. Under this umbrella are some plants that have been given species ranking, including I. florentina, originally cultivated extensively in Italy for the production of orrisroot; I. germanica var 'Atropurpurea', introduced in the 19th century from Kathmandu, with red-purple flowers; and I. squalens, an early hybrid in shades of violet-gray, of interest to hybridizers because of its ruffled petal edges.

I. albicans

Is a native of Saudi Arabia and Yemen, growing in dry, rocky places up to 7200 ft (2200 m) above sea level. One of the ancestors of the bearded irises, it still grows in colonies in several southern Mediterranean countries. It is an elegant flower, usually white and sweetly scented.

I. kashmiriana

Similar to I. albicans is I. kashmiriana which comes, unsurprisingly, from Kashmir as well as India, Pakistan, Afghanistan and Nepal. Its flowers are also fragrant and have flaring falls. As a white tetraploid, it is of value in hybridizing programs.

I. albertii

Is a native of central Asia where it grows on rocky hillsides and grassy steppes. Its flowers are purplish blue, the beards white, tipped with yellow. It has widely branching stems to about 28 in (70 cm) in the wild, is early blooming, hardy and disease resistant.

I. pumila

Is probably the best-known of the smaller bearded iris species but is not as accommodating as I. chamaeiris. It must have perfect drainage and the soil should be rich in lime. The unbranched flower stem (or more correctly, the perianth tube) grows to between 1/2-4 in (1.5-10 cm) -smaller even than I. chamaeiris -and is variable in form, size and color due to the vastness of its natural habitat across the former Soviet Union and central Europe. Flower colors range from shades of yellow and blue through lilac to purple, black and sometimes maroon or ruby red. As with the blooms of I. chamaeiris, the standards tend to be larger than the falls and curve gracefully over the style arms.

I. reichenbachii

A hardy plant, growing to about 12 in (30 cm), it is widespread in its natural habitat throughout Serbia, Bosnia, Bulgaria, Macedonia, Romania and Ukraine. Yellow color of flowers is the predominant color, though it is also found in shades of lilac and purple, and it makes a showy display en masse.

I. suaveolens (syn I. mellita)

Is an attractive little plant, with flowers a shot-silk blend of bronze-brown and purple, with a tiny white beard stained blue at the tip. A native of hilly areas of Greece and other countries around the Mediterranean, this iris demands perfect drainage, loose rich soil and added lime.