Why Irises Won’t Bloom: What To Do For Iris Plants Not Flowering

Irises are one of the easiest flowers to grow. They stem from rhizomes, which quickly multiply over the years, producing bigger, wider stands of these appealing blooms. When you notice iris plants not flowering, the cause can stem from a variety of issues including weather, soil fertility, overcrowding, unhealthy rhizomes, insect or disease attack, planting depth and even site conditions. If you are wondering, “why are my irises not blooming,” take a good luck at these issues. Usually, we will find iris plants not flowering due to one of these easily corrected conditions.

Why are My Irises Not Blooming?

Bearded or Asian, classic or designer, irises are a pleasure to have in the garden. They provide a long term display of tall, glorious sword-like leaves and boldly featured blooms. Most irises have a wide hardiness range from United States Department of Agriculture zone 4 to 9. When iris do not bloom, you still have beautiful foliage but the long waited for flowers refuse to appear. Frustrating as this is, it is generally something that can be fixed and flowers will appear the following year.

There are many reasons for irises not blooming well, but what about why irises won’t bloom at all? Most species of iris spring from rhizomes, although a few come from bulbs. Both these are underground storage structures that contain a reserve of carbohydrates and embryonic plants. When temperatures and lighting are right, they sprout stems and leaves and eventually produce flowers.

Poor rhizomes or bulbs are often the cause of no flowers. If these are mushy, rotten, small and under formed, then the result is stunted plants with few or no blooms.

Also, the plant needs well-drained soil in full sun for flowers to be produced. Irises in shady locations may fail to form blooms.

Depth of planting can also cause iris plants not flowering. Rhizomes should be near the soil surface, ideally with the tops at or slightly below the soil surface.

Other Reasons for Why Irises Won’t Bloom

If plants are correctly installed, have well-draining soil and good light exposure, it may be a soil fertility problem. Conduct a soil test to see if the pH and fertility are consistent with good iris growth. Ideal iris soil pH is 6.8 and soil should have average levels of nitrogen, but sufficient amounts of phosphorus too, the nutrient that helps plants form flowers. An amendment of superphosphate, colloidal phosphate or bone meal applied in early spring can help plants develop blooms.

Another reason for iris plants not flowering is overcrowding. The rhizomes will increase over time and plants become too packed in their site. Dig up the clump and divide it, planting each rhizome individually in other areas of the garden. Retain just half the rhizomes in the existing area and water all transplanted rhizomes frequently.

Over competition from other plants and weeds, which shade the iris bed, and insufficient water are other causes for why irises won’t bloom. Irises are extremely drought tolerant but in the absence of any water, they will respond by refusing to bloom.

Another commonplace reason is a late freeze. Although irises tolerate freezing conditions well when not sprouted as long as the area is well draining, early leaves and stems can succumb to a freeze. When there are no leafy greens to draw in solar energy, flower production can screech to a halt. Also, a freeze can kill any new buds that are just forming. Freezes experienced by plants 6 to 8 weeks before bloom can simply abort the buds and prevent iris plants from blooming for a season.

Insects and disease are seldom a problem, but if plant health is compromised, buds will rarely form.

Removing Siberian Iris Flowers – Does Siberian Iris Need Deadheading

Known as the most adaptable, easy-to-grow iris plants, Siberian irises are finding their way into more and more gardens these days. With beautiful blooms in multiple colors, their dramatic but tough sword-like foliage, and excellent disease and pest resistance, there is no mystery why iris lovers are drawn to them. Siberian irises are known as a low to no maintenance plant, yet here at Gardening Know How, we are flooded with questions like “should you deadhead Siberian iris?” and “does Siberian iris need deadheading?” Click on this article for answers to those questions, as well as tips on removing Siberian iris flowers.

About Siberian Iris Deadheading

Siberian iris plants naturalize, forming clumps or colonies of 2- to 3-foot (.61-.91 m.) tall plants in zones 3-9. Blooms form from spring to early summer on strong, erect stems above stiff sword-like foliage. They bloom along with other spring perennials such as allium, peony, bearded iris and foxglove. One of the notable characteristics is that their stems and foliage remain green and erect after the blooms fade. They do not brown, scorch, wither or flop after blooming like other irises often do.

Though the foliage will last a long time, Siberian irises only bloom once. Removing Siberian iris flowers once they’ve wilted will not cause the plants to rebloom. Wilted, spent blooms of Siberian iris can be removed to improve the tidy appearance, but deadheading spent flowers is purely cosmetic and has no actual effect on the health or vigor of the plants. Because of this, they can be paired with plants that flush out later, such as daylily, tall phlox or salvia for successive blooms.

How to Deadhead a Siberian Iris

If you enjoy deadheading plants and prefer a pristine garden, deadheading Siberian iris blooms will not harm the plant either. For best plant appearance when removing spent Siberian iris blooms, cut the whole flower stalk back to the plant crown immediately after the flowers fade.

Take care, however, not to cut back the foliage. This foliage photosynthesizes and collects nutrients throughout the growing season. In autumn, the leaves will begin to dry up, brown and wither as all the stored nutrients move down into the root system. Foliage can be cut back to about 1 inch (2.5 cm.) at this point.

How to Prune Water Iris

Water iris is a group of flowering iris that can grow well and thrive in either moist to boggy soil or in shallow water up to 3 inches over the crown of the plant. There are several iris cultivars that have this planting flexibility including iris laevigata and iris pseudacorus. They should be pruned in the summer or early fall after blooming only as needed to deadhead spent flowers or remove damaged or diseased foliage.

Remove wilted iris flower heads on their short stalks after the bloom has faded and begun to die back. Repeat this process throughout the growing season to keep the stand looking tidy. Place the cut just at the bottom of the flower stalk but leave the surrounding and lower foliage that encases the flower stem in place. Lift the cut spent flower heads out of the plant canopy and compost or discard.

Prune water iris foliage that is damaged, appears diseased or is discolored by cutting just the damaged leaf down to the crown of the plant. Leave all healthy foliage in place to capture sunlight and feed the underground rhizome. Pull the ailing leaves that have been cut from the plant and discard in the trash to prevent the spread of disease or pest activity.

Prune water iris foliage down to one half to one third of the plant height before digging and dividing the rhizomes in the early fall. This will reduce stress, shock and die back once the rhizomes are transplanted in their new location.

Many of us are accustomed to cutting back our ornamental grasses in late winter to get rid of dead leaves and promote fresh, attractive growth.

You might wonder if it’s also necessary to cut back grassy irises such as bicolor (Dietes bicolor) or African (D. vegeta) — plants that also sport the long, slender leaves common to grasses.

We’ll look at the taxonomy of these plants, and then get down to brass tacks about whether you should be cutting them back.

What’s in a Name?

Just so we’re on the same page about what plants we’re talking about, let’s get some confusing nomenclature business sorted out. The genus for this group of rhizomatous plants is Dietes, which is a part of the family Irideceae.


These plants were once classified in the genus Moraea but were kicked out because they have rhizomes, as opposed to Moraea, which have corms. Corms are a different type of underground plant stem, one that’s more bulbous.

All this is to say there are almost as many names for these long-leafed beauties as there are stars in the sky, so don’t be dismayed if you call them tomato and your neighbor calls them toe-mah-toe.

Herein, we’re referring to species in the genus Dietes, and you can apply the instructions below to plants commonly known as African iris, bicolor iris, fortnight lily, butterfly iris, Japanese iris, wood iris, and probably untold other nicknames.

Start with Routine Maintenance

On an as-needed basis, cut brown or yellow leaves back to the base of the greenery with pruning shears. Cut sharply and cleanly straight across the leaf blade, near the crown of the plant.

If you want to prevent the plant from self-seeding, cut just under the green seedpod with scissors to remove it.

You can pinch or clip spent blooms, but don’t remove a healthy-looking flower stalk. It will continue to produce many more blooms.

At some point, however, the flower stalk’s decline will become evident, and you can prune it back to the crown.

The Big Chop: Yes or No?

The short answer is yes, it’s perfectly okay to completely cut back your Dietes.

This bicolor iris was chopped back in late winter and produced new leaves almost immediately. Still, the plant could use a little cleaning up. Photo by Gretchen Heber.

A wholesale cut, as you would do with ornamental grasses, is definitely in order if you’ve neglected your Dietes for several years and there are more brown and yellow leaves than green.

After cutting the entire plant back to ground level with hedge clippers, the plant will joyfully return to life, come springtime.

You’d preferably do this cutting in fall, but don’t sweat it if you’re unmotivated to get out there until the weather has warmed up.

Gardeners have waited well into spring, even when new growth was percolating, before bringing out the big guns and giving the plant a shave. And the plant has survived quite nicely.

It’s a good idea to thoroughly water these normally drought-tolerant plants after a haircut, and offer a balanced fertilizer with equal amounts of nitrogen, phosphorous and potassium to help promote new growth.

Sharpen Your Tools

So, in the midst of carefully pruning your crape myrtle trees and tending your winter lettuces, don’t forget to have a look at your grassy irises and assess whether they could use a little touch-up clipping, or perhaps even a wholesale cut back.

An abundance of fresh, green, spiky foliage will be your reward for a chop well done.

How do you care for your bicolor or African irises? Do you have another name for them? Tell us in the comments section below!

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Pruning photo by Gretchen Heber, © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for
more details. Uncredited photos: .

About Gretchen Heber

A former garden editor for a daily newspaper in Austin, Texas, Gretchen Heber goes through entirely too many pruners and garden gloves in a year’s time. She’s never met a succulent she didn’t like and gets really irritated every 3-4 years when Austin actually has a freeze cold enough to kill them. To Gretchen, nothing is more rewarding than a quick dash to the garden to pluck herbs to season the evening meal. And it’s definitely time for a happy dance when she’s able to beat the squirrels to the peaches, figs, or loquats.

Iris spuria (Blue Iris)

Native to central and southern Europe, spuria irises are one of the tallest of irises, reaching a height of 3-5 ft or more (90-150 cm). Generally blooming 1 to 2 weeks after the Tall Bearded Irises, spuria irises are elegant rhizomatous perennials with attractive beardless flowers with slim standards and falls, up to 6 in. wide (15 cm). Graceful, the flowers exist in a wide range of colors, including bicolors, bitones and halos, and provide a striking display in late spring to early summer. Growing in clumps with handsome narrow linear leaves to 1 ft. long (30 cm), they add drama to the garden and will reward you with beautiful blooms and long-lasting cut flowers.

  • Each flower stalk generally bears 3 to 4 buds on each branch. It should be noted that both height and bud counts may vary with regions: shorter stalks and reduced bud counts will be obtained in colder climates than in warm climate areas.
  • spuria irises seem to set seed easily and will naturalize into large clumps.
  • spuria irises attract bees and butterflies and are usually deer resistant.
  • spuria irises perform best in full sun, in rich, humusy, medium moisture, neutral to slightly alkaline, well-drained soils. Partial shade is tolerated, especially in areas that have extremely high temperatures in the summer. However, both flowering performance and disease resistance may be altered. While consistent moisture should be provided during the growing season, wet soils are to be avoided to avoid rot issues. Less moisture is needed after blooming since most spurias are summer dormant (Do not water your spuria irises when dormant as this will cause rot). Once established, spurias are drought resistant. They are very heavy feeders, so make sure you fertilize them regularly prior to bloom.
  • spuria irises make great focal points and are welcomed additions to beds, borders, wall-side borders, city gardens, coastal gardens, cottage gardens.
  • spuria irises should be planted in mid to late summer, about 2 in. deep (5 cm) and 24-36 in. apart (60-90 cm). Space them far enough apart to grow in the same location for years as spuria irises resent being transplanted. They usually do not bloom the first year after planting. The second year should produce several bloom stalks.
  • Deadhead spent flowers and remove any dying foliage in fall. Old flower stems can be cut down after blooming is over, not only for neatness, but to allow air to reach the rhizomes.
  • Divide plants immediately after flowering when overcrowding occurs (every 3-4 years). Propagate by division of rhizomes from mid summer to early fall
  • May be attacked by slugs, snails and thrips and be subject to gray molds, mustard seed fungus or crown rot.
  • Tips to get your spuria irises to bloom: (1) Don’t plant the rhizomes too deep, (2) Provide enough light, (3) Don’t over-fertilize (4) Divide your plants when overcrowded.
  • Ingestion may cause severe discomfort

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Some Interesting Facts about Iris

  • Irises come in many forms, shapes, colors and sizes and the sword-like foliage is attractive when the plant is not in bloom.
  • The Iris was named after the Greek goddess who is considered to be the messenger of love and uses the rainbow to travel. Iris was probably named after the goddess because of the numerous colors it is available in.
  • Irises are among the best-known and loved among garden plants. Irises are hardy herbaceous perennials.
  • The genus Iris is a large genus of bulbous and rhizomatous perennials.
  • The Iris was named after the goddess of the rainbow because of its many colors.
  • A flower on the Sphinx is considered to be an Iris, and another appears on a bas-relief of the time of the 18th Egyptian dynasty.
  • Pliny also knew the Iris and praised its medicinal virtues.
  • The Iris was also a favorite flower of the Moslems who took it to Spain after their conquest in the 8th century.

The Iris flower’s characteristic feature is having three petals often called the “standards” and three outer petal-like sepals called the “falls”.

Types of Irises

Irises are classified into two major groups, Rhizome Irises and Bulbous Irises. Within those groups are countless species, varieties, cultivars and hybrids, according to the American Iris Society.

Rhizome Irises are thickened stems that grow horizontally, either underground or partially underground. After planting, iris rhizomes produce sword like leaves that overlap, forming flat fans of green foliage. Three popular irises in this group are Bearded, Beardless and Crested Irises.

  • The bearded iris has four distinct parts: the Standards, Falls, Stigma flaps, and Beard
  • The beardless variety has: Standards, Falls and Stigma flaps, but usually have crests
  • The crested Irises or Evansia Iris has: Standards, Falls and Stigma flaps and in addition to a ridge on the falls of the blossom, they have ridges like crests instead of beards

Crested irises are often considered in the same manner as the beardless iris. These plants spread freely by underground stems and produce flat flowers in the shades of blue, violet and white. Often the flowers and leaves are found on bamboo like stems which can vary in height from 5-200 centimeters in height.

Varieties of Bearded Iris Varieties of Beardless Iris
Miniature Dwarf Bearded Iris Siberian Iris
Dwarf Bearded Iris Japanese Iris
Intermediate Bearded Iris Louisiana Iris
Border Bearded Iris Dutch Iris
Miniature Tall Bearded Iris Yellow Flag Iris
Tall Bearded Iris Blue Flag Iris

Bulbous irises grow from bulbs that require a period of dormancy after they have bloomed. The bulbous irises are typically smaller than rhizome irises and usually produce smaller blossoms.

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Growing Irises

Before planting Iris, improve the soil conditions by using a slow release fertilizer. To increase the organic matter content, use compost, peat moss or well-rotted manure. Fertilizer and organic matter should be worked thoroughly into the top 4 to 6 inches of soil.

  • Wooded areas with good drainage and partial shade are ideal spots for the crested iris.
  • Irises are grown from both seed and root separation.
  • The roots or rhizomes, are easily separated and replanted.
  • The rhizome looks like a long, thin potato with roots underneath.
  • When transplanting, separate the rhizome. Make sure to have some root and a leaf or two in each section.
  • Plant the rhizomes near the surface with the roots below.
  • Divide the clumps and plant single rhizomes, spacing them 8 to 18 inches apart according to the effect desired.
  • Spade a planting hole about 10 inches deep and work 1 tablespoonful of fertilizer into the soil in the bottom of the hole.
  • If the soil is heavy, some drainage material such as gravel or broken pottery should be placed in the hole.
  • Fill the hole with loose soil and place the root section so that it will not be covered more than 1 inch deep.
  • Most Beardless Irises can also be propagated from seeds.

The Dykes Medal is awarded annually to the finest iris of any class. Tall bearded irises have won the Dykes Medal more often than any other class.

Iris Plant Care

  • Apply a thin layer of compost around the base of plants each spring, leaving the rhizome exposed.
  • As flowers fade, cut back the flower stalks to the base of the plant.
  • To encourage a second bloom on re-blooming varieties, promptly remove faded flowers and maintain consistent watering throughout the summer.
  • In autumn, trim away dead foliage and prune back healthy leaves to a height of 4 to 5 inches.
  • Once the soil has frozen, apply a layer of mulch to help prevent roots from heaving out of the soil during alternate freezing and thawing.
  • If heaving occurs, don’t try to force plants back into the soil. Instead, cover rhizomes and exposed roots with soil.
  • Divide bearded irises every 4 to 5 years, preferably in late summer. Each division should have one or two leaf fans. Older rhizomes that have few white feeding roots should be discarded.

Want to learn more about growing Irises and other flowers? View books on Gardening

Other Uses of Iris

  • The juice of the fresh roots of Iris, bruised with wine, has been employed as a strong purge of great efficiency in dropsy.
  • Iris roots are used to treat skin diseases. The juice of Irises are also sometimes used as a cosmetic for the removal of freckles on the skin.
  • The fresh root of the Iris germanica is a powerful cathartic, and for this reason its juice has been employed in dropsy. It is chiefly used in the dry state, being said to be good for complaints of the lungs, for coughs and hoarseness, but is now more valued for the pleasantness of its violet-like perfume than for any other use.
  • Iris flowers are used as a liver purge.

Purple Iris

  • Purple Iris Flowers bloom for two to three weeks in the late spring to early summer.
  • The Purple Iris is the state flower of Tennessee.
  • The Purple Iris can be grown in your home, in containers.
  • The majority of Iris flowers are in Purple.

Also have a look at some other Flowers

Rose Flower Daisy Flowers Jasmine
Tiger lilies Lily Flower Marigold
Cosmos Flowers Morning glory Larkspur Flower
Peony Flower Sampaguita Daffodils
Lisianthus Agapanthus Gladiolus
Carnations Tulips Summer Flowers
Exotic Flowers Tropical Flowers Spring Flowers

Blue iris (Iris versicolor) and strict blue-eyed grass (Sisyrinchium montanum)

July 2016

Two members of the iris family, one large, one small, Iris versicolor is a long-lived perennial with large purple flowers; Sisyrinchium montanum is short-lived, but readily self-seeds. Iris versicolor ranges from Maine west to Nebraska, south to Arkansas; Sisyrinchium montanum is common from Maine south to Virginia.

By Pamela Johnson

There are native plants, shrubs, and trees that occupy enough uncultivated ground to capture attention whenever their salient features announce themselves: a long swipe of native hawthorn (Crataegus spp.) that enlivens and colonizes a stretch of roadside; a bridge embankment improbably cascading with American trout-lilies (Erythronium americanum ssp. americanum) like a terrestrial fish ladder; or the deep green gloaming of hemlock (Tsuga canadensis) woods suddenly illuminated by its new, tender, chartreuse growth. The revelations are everywhere in all seasons, reminders to anticipate, perhaps to remember and monitor plant populations from year to year.

A meadow passed almost daily has small, but salutatory eddies of blue iris (Iris versicolor) among its treasures, which also include glimpses of bobolinks and an occasional American bittern standing sentinel and believing itself to be well hidden in the alder thickets. This year, the meadow is not floriferous, but an old adjacent horse corral is blue with bloom, as if patches of late-day sky had fallen to earth, abandoned at dusk. The proportion of flowers overwhelms the foliage—all blue-violet with only a few exclamatory spears of green.

Concomitantly, a search for previously seen sweeps of strict blue-eyed grass (Sisyrinchium montanum) has been disappointing. There are a few plants, but not the usual saturation like that described by Mrs. William Starr Dana in 1894:

. . . the blossoms of the blue-eyed grass . . . so large and abundant that they seem to float like a cloud of color on the tops of the long grasses.

There isn’t anything necessarily sinister about these fluctuations in plant numbers, or slight shifts in distribution. Wildflower populations respond to many cues, suffer deficits, and enjoy bounteous seasons. Unnatural disturbances are patent; natural changes require lengthy observance. Blue flag iris and blue-eyed grass are members of the same family, the Iridaceae, but the two plants would not necessarily exhibit parallel behaviors or undergo the same changes.

In Maine the iris family contains a small parcel of representatives. Three species of the genus Iris are recognizably iris-like, simpler-looking forms of the old-fashioned garden irises. The other iris genus is Sisyrinchium with four species and two varieties, all these not immediately recognizable as iris flowers.

Sisyrinchium montanum is a taxonomic mouthful for the diminutive blue-eyed grass. Some may find the plant inconsequential, easily mistaken for a few blades of grass when not in bloom. Certainly it contrasts with the frilly-headed hybrid garden irises that flounce onto June’s horticultural stage and exit quickly, leaving unattractive foliage behind.

Strict blue-eyed grass is short (usually only four to eight inches tall) with a fan of rapier leaves rising from a small fist of shallow yellow roots. When the flowers begin to open in mid-May, blue-eyed grass is arresting. Profoundly blue to blue-violet, the flowers seem bigger than they actually are because their color has such depth. There may be several flattened flower stalks with multiple buds on a plant, but only a single flower opens on each stalk, and only in sunlight. This ought to be one of the first wildflowers taught to a child—small stature, compact beauty, ease of identification (at least at the genus level ), and perhaps even evocative of a particular field where the plants grow in lively abundance.

Iris versicolor, blue iris, is also easy to spot and identify in Maine, though there are two similar species found only in eastern central counties. Iris versicolor is a natural hybrid of one of those species, Iris hookeri, and of another native iris, Iris virginica, found farther south. Blue iris in an interspecific hybrid, an allopolyploid, that reproduces “true to seed”; anyone interested in Iris versicolor’s chromosomes may refer to “Parental Origin and Genome Evolution in the Allopolyploid Iris versicolor” Annals of Botany, Oxford Journals, Volume 100, Issue 2 (June 25, 2007)—or not.

Blue iris (or blue flag) blooms exuberantly in early June, the flowers lasting sometimes throughout the month. There are usually several flower stalks per plant, with the buds and blossoms (opening one at a time) held just above the sword-like leaves.

Both blue iris and blue-eyed grass possess markings on their petals and sepals called nectar guides. These striations and veinings are dark blue to deep purple, colors irresistible to bees and wasps of the Hymenoptera family. Not surprisingly blue iris and blue-eyed grass are pollinated by bumblebees (Bombus spp.); by mason bees (Osmia spp.), sweat bees (Halictidae), and digger bees (Anthophorini spp.); and by syrphid flies (Syrphidae).

There is nothing subtle about the patterns of nectar guides. The flower petals and sepals provide a bee-sized landing strip and the markings are like runway signs guiding the insects precisely to deposit and retrieve pollen. Blue iris has its female parts facing away from its anthers (male organs) to prevent self-pollination. Blue-eyed grass embellishes its flower center with a bright yellow star—yellow is another bee-favorite—to further announce the treats within.

Flowers advertize by color, structure, odor (sometimes fragrant, sometimes fetid), all mechanisms to attract invertebrate, avian, and a few mammalian pollinators to accomplish sexual reproduction. As much as humans admire, and covet, the wonderful panoply of flowering plants, our perception of their beauty is irrelevant to the complexly evolved and essential arrangement between insects and flowers.

That said, irises have been part of human history for millennia. Egyptian tomb friezes depict the unmistakable militant foliage and helmut-like blooms of irises. Frescoes at Knossos that survived the destruction of the Minoans in 1450 BC, show irises, along with violets, lilies, and the earliest discovered representation of roses. An Assyrian, King Tiglath-Pileses I (1114-1026 BC), cultivated gardens that included irises. Pythagoras, the Greek philosopher, used the trimerous petals and falls of an iris to define mathematical perfection.

Many plant historians believe that some species of iris got their names through Alexander the Great’s march to the Indus River in the 4th century BC. Since many irises originate in Asia Minor, it is not surprising to see the flowers used as a motif in art and architecture, from ancient Mediterranean cultures all the way to the Mughals in 16th century India.

Celebrated and traded, what was found in the East made its way back along the Silk Road, eventually north into Europe. The 6th century Frankish King Clovis I adopted the iris as the symbol of his conversion to Christianity. It was Louis le Jeune, in the 12th century, who appropriated the iris as his particular royal emblem; the fleur-de-lis, now often translated as a lily, was actually the iris, the flower of Louis. The familiar tripartite symbol has a petal each for wisdom, faith and valour.

Irises and lilies were commingled in medieval herb gardens, (their names and identites were often muddled until Linnaeus clarified the genera in 1753). Apart from beauty and symbolism, irises provided their roots to the important medicament and preservative orrisroot powder. The rhizomes of many Old World iris species are large, fleshy storage units, nutritional caches against the harsh xeric challenges of their montane origins. It was a natural hybrid of two iris species from Turkey’s Taurus Mountains that eventually delivered Iris x germanica, the garden iris to Europe, and on to the New World. North America returned the favor, sending its native irises, genetically closer to Japanese and Siberian irises, to England in the 17th century. Given the similarity in form between blue iris and the popular nursery varieties of the Far Eastern species, it is surprising that Iris versicolor is not seen more often in gardens.

Not every garden accommodates every wild plant. Spring ephemerals that luxuriate in cool humus, and beneath the filtered light of a tree canopy not yet full of leaves, will suffer in the sunny exposure of a traditional border garden. Woodland plants, herbaceous or woody, usually do better with protection from summer’s scorching afternoon sunlight. Ericaceous plants that like lean soils are at odds with the demands of common border gluttons like hollyhocks, clematis or hybrid roses. And there are always the incompatibilities of color, size, and form. Some native wildflowers look best when allowed to roam freely among their natural cohorts where they can also be planted in sufficient numbers that will benefit insects and other wildlife.

There are no constraints with either Iris versicolor or Sisyrinchium montanum. Both fit handsomely in formal or informal gardens and landscapes.

Iris versicolor is usually described as a wetland species, and while it thrives in damp meadows, it is tolerant of drier situations. It also blooms in full sun as well as partial shade. In bright sun, Siberian and Japanese irises require richer, moister situations than blue iris; and the non-native species require more frequent division to maintain blooms.

Iris seedpod

In spite of hosting various insects on its leaves, Iris versicolor’s foliage is appealing year-round, turning yellow-orange in autumn. Its seed capsules also provide interest to the garden’s winter mien. A low spot of ordinary soil could be transformed with a planting that weaves Iris versicolor, sensitive fern (Onoclea sensibilis), and common soft rush (Juncus effuses).

Sisyrinchium montanum is also suited to different garden situations, even dry ones if its roots are not disturbed. These small plants are happiest where they can roam by seeding themselves. Blue-eyed grass is delightful mixed with three-toothed cinquefoil (Sibbaldiopsis tridentata) as edging plants. The latter is an underutilized groundcover with shiny leaves, orange, red and deep green in autumn; its stalked white flowers coincide with those of blue-eyed grass. Low-growing pussy-toes (Antennaria spp.) and silverweed (Argentina anserina) have gray and silvery-green foliage, respectively; their leaves would accent the bluish green of blue-eyed grass’s leaves. It is always prudent to think of the virtues of foliage, along with the evanescence of flowers. Blue-eyed grass’s seed capsules are small green beads that darken as the seeds ripen—another sweet feature of this plant.

The seeds of iris and blue-eyed grass can be stored dry in a paper bag after collection, then sown out of doors in the fall or early winter. Germination occurs in mid-spring, and most plants will bloom during their second summer.

Visit our shop to purchase blue iris seeds and blue-eyed-grass seeds.

Dana, Mrs. William Starr. 1895. How to Know the Wild Flowers. New York; Charles Scribner’s Sons. p.302.
Arthur Haines in Flora Novae Angliae is not the only botanist to counsel against glib identifications of the different species of blue-eyed grasses. There is much to appreciate, however, even with a rough idea of which species is which.
The Greek language provided the genus names of Iris and Sisyrinchium; a logical choice for Iris, from goddess of the rainbow, and a nod to the many flower colors of Mediterranean species; Sisyrinchium is problematic, translated as pig’s snout, goat’s skin, or woolen tunic- no one seems to find these appropriate.
One of these is the wasp mimic the Virginia Ctenucha (Ctenucha virginica), a day-flying moth; another inquiline is the Clubiona spider who folds iris leaves, lays her eggs, dies, and leaves her body behind to feed her offspring.

By George Weigel/The Patriot-News

Q: I have reblooming irises. How do I prune them?

A: Very much like May-blooming ones, except you’ll repeat the process in fall. Cut off the flower stalks in June after the first flush of flowers fade, but don’t remove the foliage.

Come early fall, your plants should send up new flower stalks until frost. These flower stalks also can be removed right after flowering is done. If a killing frost is forecast and you still have new blooms and buds that are ready to open, cut those and take inside in a vase.

Unless you’re having trouble with leaf spot or borers, don’t cut off any leaves so long as they’re green and healthy. I even let my healthy leaves stand all winter and clean up the wilted and winter-damaged leaves in early spring before new growth begins.

Some growers routinely cut all iris leaves nearly to the ground in late summer to prevent borers from working their way down the leaves and into the rhizomes, where they can destroy the plants. This would short-circuit borers but would at least delay if not abort your second round of flowering. Borers aren’t a given problem, but if you run into them, a soil treatment of liquid Merit (imidacloprid) in early April will control them all season.

Keep in mind that rebloomers use more growing energy than once-bloomers so they should be fertilized at least twice a year – once in early spring and again right after the first round of blooming. Use a product that’s low in nitrogen (the first number on the fertilizer label) and high in phosphorus (the second number). Something like Espoma’s Bulb-tone or a product with a breakdown of 5-10-5 would be fine.

You’ll find lots more great growing details on reblooming iris at the Reblooming Iris Society’s web page of http://www.rebloomingiris.com/culture.htm.

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