Blue flag iris bulbs

The Friends of the Wild Flower Garden, Inc.

Blue Flag is a plant of marshes and wet meadows, growing 1 to 3 feet high on solid stems.

Leaves are sword shaped, 20 to 40 inches long, green to grayish-green color and prominently veined, with a raised (thickened) mid-rid in mature leaves. As basal leaves, they rise from the root in a fan shape, erect, and then later drooping. The flower stem may also have a few leaves and these are usually short and do not rise above the flower stalk.

The inflorescence consists of 2 to 4 flowers, that are similar to many beardless iris, at the top of a solid stem that rises from the root. Stems may branch once and may have some stem leaves. The upper section of the stem under each flower forms a spathe covering the ovary of the flower. Bloom time is the end of May to the end of June in this part of Minnesota depending on the season’s weather.

Flowers are blue to purple (are rarely white), about 4 inches wide and are similar to many beardless iris. The three outer ovate violet-blue sepals spread outward; the base narrows abruptly with a hairy greenish or yellowish patch surrounded by white, lined with purple veins – this area being known as a ‘signal’. The Garden plants have a yellow spot. Very showy. The petals (often called ‘standards’ in the Iris genus) are the same color but are oblong, much shorter that the sepals, have smooth margins and are upright. The fruiting parts are in the center of the flower. The styles form flat arms, with curled tips and smooth margins, which reflex outward and lie atop the base of the sepals with the anthers and stigma hidden from view between the two protecting the pollen from rain. The nectar of the plant is in glands at the base of the petals.

Fruit: The seed forms in a somewhat 3-sided cylindrical capsule, each side has 2 rows of seeds which are thin, D-shaped, and hard (not corky like I. pseudacorus). These capsules often overwinter. Seeds are distributed by wind when the capsule opens. These seeds require at least 120 days of cold stratification for germination and are thus best propagated by sowing outside in the fall.

Habitat: The root stock is a branching rhizome with fleshy roots. Branches are the same size and texture as the main rhizome (said to be ‘homogeneous’). Propagation is by seed or single rhizomes cut from the main root stock. The plant will spread vegetatively to form large clumps if left undisturbed. While the plant has few pests or diseases, it can be overgrown by more aggressive plants. However, in wet grazing meadows it may be weedy as grazing animals will not eat it but do eat its competitors. I. versicolor requires a wet meadow or marshy area with full sun to grow best.

Names: The genus name, Iris, is after the Greek goddess of the rainbow. The species, versicolor, means ‘variously colored’. The author name for the plant classification, ‘L.’ is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.

Comparison: The other iris in the Garden marsh is Yellow Flag Iris, Iris pseudacorus L. This is a non-native iris considered to be an invasive species, but has been allowed to exist in the Garden under control. Of closer resemblance is I. virginica, the Southern Blue Flag where the only visual difference is that the signal area is a pubescent yellow only without the yellow patch being surrounded by the purple-on-white veined area.

Irises of South Florida

The beautiful irises of South Florida include African, walking, blue flag, and one called blackberry lily.

These striking plants make great accents for their foliage alone, but all have exquisite flowers as well.

The unique way that most plants of this type flower is to send up a shoot that looks just like a leaf.

Then a bud appears on the side near the top, opening into a delicate and colorful blossom.

The classic upright foliage fans out and complements other textures and plant growth patterns. Some have wider leaves, others are more narrow.

African Iris (Dietes vegeta) – also known as “Butterfly Iris” (pictured above) – is probably the best known in South Florida landscapes.

Its thin, willowy, upright leaves grow in a clump that forms a grass-like mound about 2-1/2 feet tall.

This plant blooms on and off all year with bright white flowers dabbed with lavender and gold. Another lesser-used variety has small, soft yellow flowers with a purplish-red center.

Walking Iris (Neomarica spp.) is so named because, as the flower stalk gradually leans low to the ground, it roots and “walks.”

These plants come in flower colors of yellow, white and blue. Especially beautiful is the lavender-blue and white blossom of the cultivar called Apostle Iris (pictured below).

They bloom on and off during warm months, growing to about 3 feet tall. This plant is similar in looks to African Iris, but with wider leaves..

Blue Flag (I. virginica) blossoms in spring with gorgeous flowers in a vibrant lavender blue. It’s a native plant to Florida (and much of the Southeast U.S.).

Blue Flag grows about 2 to 3 feet tall, preferring part shade. This is a good choice to plant by a pond since it will grow in very wet areas.

Blackberry Iris (Belamcanda chinensis/Iris domestica) is often called “Blackberry Lily” because of its flowers look more like lilies than irises.

This plant does best in part sun to part shade.

It sends flowers up on thin stems above the wide leaves, growing to about 2 feet tall with flowers reaching about 18 inches above.

When a stalk finishes flowering, it produces seed pods that open to reveal little black “berries.” Then it slowly turns brown. Cut off the browned stalk all the way to the ground to tidy up the plant and let new growth take over.

Blooms are a soft orange with reddish freckles, though a newer variety with brighter multi-colors has been recently introduced.

Plant specs

These plants will grow in full sun but seem happiest in part sun to part shade. Growth rate is moderate.

Heights vary by variety, averaging 2 to 3 feet tall.

Blue Flag and Blackberry Iris are cold hardy, growing anywhere in South Florida. The others prefer the warmth of Zone 10.

Though these plants will spread they don’t do it in a hurry, so you can remove any shoots that are going places where you don’t want them.

Though they like a good bit of moisture, it’s best to place them in a well-drained area (the exception is Blue Flag, which can handle very wet soils).

Plant care

Add top soil or organic peat moss to the hole when you plant. Because this plant does best with plenty of water, you may want to add water-retention crystals when planting, especially if other plants nearby like it more dry. (For more info on this, see the page on Watering.)

Trimming is usually necessary to remove any browned leaves and spent flower stems. Cut these as close to the ground as you can.

Avoid a complete cutting back of the plant, however.

You can also deadhead if you like, especially with the walking variety to limit its spread.

Water is very important – they need a regular drink and don’t mind “wet feet” occasionally.

Fertilize 3 times a year – in spring, summer, and fall – with a good quality granular fertilizer. You might like to supplement feedings with bone meal and/or liquid fertilizer for year-round bloomers like African and blackberry iris.

Plant spacing

Place these plants about 2-1/2 feet apart. Come out from the house 2 feet. When planting along a walk or drive, come in 3 feet to allow for future spread.

You can grow this plant in a container, though it’ll really come into its own when planted in the ground.

Landscape uses for irises

  • around a landscape boulder
  • accent for a mixed bed
  • along a porch or deck
  • surrounding a palm
  • front of the border (African and Blue Flag)
  • lining a walk
  • foundation plant
  • around a tree trunk
  • by the mailbox or lamppost

COMPANION PLANT SUGGESTIONS: In a part shade area, try downy jasmine, tibouchina grandifolia, firespike and pentas.

Other plants you might like: Heliconia, Butterfly Ginger

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Wildflowers of the Adirondacks:
Blue Flag (Iris versicolor)

Wildflowers of the Adirondacks: Blue Flag’s sword-like leaves emerge from thick horizontal root stock. Blue Flag at Cemetery Road Wetlands in Essex County, New York (12 June 2018).

Blue Flag (Iris versicolor) is a native iris that grows in wetlands in the Adirondack Mountains of upstate New York. It produces showy violet-blue flowers in early summer.

This plant is also called Northern Blue Flag, Larger Blue Flag, Harlequin Blueflag, and Wild Iris. The name “flag” is from the middle English word “flagge,” meaning rush or reed. Iris flowers are said to symbolize power, with the three parts representing wisdom, faith and courage.

Identification of the Blue Flag

Wildflowers of the Adirondacks: Blue Flag produces showy violet-blue flowers in early summer. Blue Flag (Iris versicolor) blooming on the edges of Heron Marsh (23 June 2018).

Blue Flag grows about 2-3 feet tall with long, narrow leaves (1/2 to 1 inch wide) of bluish green. It produces several striking, violet-blue flowers. The down-curved violet sepals are veined in yellow and white. The flowers are 2.5 to 4 inches wide.

Blue Flag flowers in early summer in the Adirondacks.

  • A tally of flowering dates for the upland Adirondack areas compiled by Michael Kudish, based on data collected from the early seventies to the early nineties, lists 16 June as the earliest date of flowering and 27 June as the median date.
  • Flowering dates from more recent years suggest that Blue Flag has been blooming somewhat earlier.

Blue Flag plants are pollinated by bees and, like other plant species pollinated by bees, have evolved special types of flowers that are easy for bees to find. Blue Flag has large lobes that bees use as landing platforms and special markings directing bees to the nectar glands.

Uses of Blue Flag

Wildflowers of the Adirondacks: In the past, Blue Flag was a popular medicinal plant among some native American groups. Blue Flag (Iris versicolor) blooming on the edges of Heron Marsh (13 June 2013).

In the past, Blue Flag was a popular medicinal plant among some native American groups. Although Blue Flag is poisonous, Native Americans and colonists dried the rhizome of the plant and used it in small amounts as a cathartic and diuretic. In addition, some native Americans reportedly used the two outermost fibers of the leaves to spin twine. Powdered iris root has also been added to perfume and potpourri.

Wildlife Value of Blue Flag

Blue Flag has limited value as a food source for wildlife. Several non-pollinating nectar feeders are frequent flower visitors, including Harris Checkerspot and Hobomok Skipper. Blue Flag also attracts bees and hummingbirds.

Distribution of Blue Flag

The native distribution of Blue Flag includes the northeastern part of the US, south to Virginia. In Canada, its distribution spans from Newfoundland to Manitoba.

In New York State, Blue Flag is found in nearly all counties in the eastern part of the state. It has been documented growing in all counties within the Adirondack Park Blue Line.

Habitat of Blue Flag

Blue Flag grows in poorly drained soils and the shallow water on the edges of marshes. It is shade intolerant. It will tolerate water to a depth of one to two feet. This plant is abundant in several ecological communities in the Adirondack Park:

One of the most convenient places to study this plant is Heron Marsh at the Paul Smiths VIC, where it grows on the edges of the marsh, together with cattails and sedges. Listen for a chorus of amphibians that breed on shallow emergent marshes, including Northern Spring Peeper, Green Frog, and Wood Frog. Birds commonly seen flitting about Blue Flag plants include Swamp Sparrow, Common Yellowthroat, and Red-winged Blackbird.

Michael Kudish. Adirondack Upland Flora: An Ecological Perspective (The Chauncy Press, 1992), pp. 23-28, 233.

New York Flora Association. New York Flora Atlas. Blue Flag. Iris versicolor L. Retrieved 18 March 2017.

United States Department of Agriculture. The Plants Database. Harlequin Blueflag. Iris versicolor L. Retrieved 18 March 2017.

United States Department of Agriculture. NRCS National Plant Data Center & the Biota of North America Program. Plant Fact Sheet. Blue Flag. Retrieved 18 March 2017.

Flora of North America. Blue Flag. Retrieved 18 March 2017.

New York State. Department of Environmental Conservation. New York Natural Heritage Program. Ecological Communities of New York State. Second Edition (March 2014), pp. 48-49. Retrieved 17 October 2015.

New York Natural Heritage Program. 2015. Online Conservation Guide for Medium Fen. Retrieved 14 March 2017.

New York Natural Heritage Program. 2015. Online Conservation Guide for Rich Shrub Fen. Retrieved 14 March 2017.

New York Natural Heritage Program. 2015. Online Conservation Guide for Rich Graminoid Fen. Retrieved 14 March 2017.

New York Natural Heritage Program. 2015. Online Conservation Guide for Shallow Emergent Marsh. Retrieved 22 February 2017.

New York Natural Heritage Program. 2015. Online Conservation Guide for Silver Maple-Ash Swamp. Retrieved 6 March 2017.

New York State. Adirondack Park Agency. Preliminary List of Species Native Within the Adirondack Park Listed Alphabetically by Scientific Name and Sorted by Habit. Volume 1. Updated 10.23.2006. Retrieved 26 January 2017.

John Eastman. The Book of Swamp and Bog: Trees, Shrubs, and Wildflowers of Eastern Freshwater Wetlands (Stackpole Books, 1995).

Lady Bird Johnson Wildflower Center. Native Plant Database.

Plants for a Future. Database.

University of Michigan. Native American Ethnobotany. A Database of Foods, Drugs, Dyes and Fibers of Native American Peoples, Derived from Plants. Iris versicolor L. Harlequin Blueflag. Retrieved 18 March 2017.

Anne McGrath. Wildflowers of the Adirondacks (EarthWords, 2000), pp. 60, 89.

Doug Ladd. North Woods Wildflowers (Falcon Publishing, 2001), p. 47.

Lawrence Newcomb. Newcomb’s Wildflower Guide (Little Brown and Company, 1977), pp. 120-121.

Roger Tory Peterson and Margaret McKenny. A Field Guide to Wildflowers. Northeastern and North-central North America (Houghton Mifflin Company, 1968) pp. 314-315.

William K. Chapman, et al. Wildflowers of New York in Color (Syracuse University Press, 1998), pp. 122-123.

National Audubon Society. Field Guide to Wildflowers. Eastern Region. (Alfred A. Knopf, 2001), pp. 571-572, 611.

Wildflowers of the Adirondack Park


FIRST IMPRESSIONS: Iris versicolor is a vigorous perennial that forms small colonies from a network of underground rhizomes. Plants produce clumps of distinctive narrow pointed leaves. In spring, foliage is topped by lovely blue irises. This unique wildflower sparkles in sunny moist or wet sites.

HABITAT & HARDINESS: Iris versicolor is native in the southern Canadian provinces from Newfoundland and Labrador to Manitoba. Plants range from Maine to Virginia and west to Minnesota and Kentucky.

This handsome iris is usually considered to be a marginal or emergent aquatic species. Plants are indigenous to marshes, swamps, shorelines, wet meadows, margins of ponds and creeks, sedge meadows and borders of wetland forests.

Plants are hardy in USDA Zones 2-7.

PLANT DESCRIPTION: Iris versicolor grows in large clumps or patches that originate from thick creeping rhizomes.

The sword shaped leaves are up to 30” tall and 1-2” wide. Leaves overlap at the base and fold around the adjacent leaf to form a flat fan-like arrangement.

In spring leafless flower stalks bear 3-5 blue-purple or violet flowers. Each bloom is 3-4” wide with darker purple veins.

The blooms have a typical iris form with 3 drooping sepals called “falls” and 3 small upright petals called “standards”. The falls are marked with a yellow blotch surrounded by a white border.

Angular capsules form after flowering. The seeds are covered in a corky deposit that allows them to distribute by floating in water.

Plants are 2-3’ tall with a 2-3’ spread.

CULTURAL & MAINTENANCE NEEDS: Iris versicolor grows best in sites with full sun or part shade. Plants thrive in moist or wet acidic soils that are high in organic matter.

This versatile wildflower prospers in clay and mucky soils, thrives in 2-4” of standing water and tolerates short periods of drought. Plants filter excess nutrients from ponds and creeks and are often planted to improve water quality. This iris appreciates a layer of mulch to protect the shallow rhizomes from sunburn. Plants are somewhat pest resistant and foliage is unpalatable to deer and other herbivores.

LANDSCAPE USES: Iris versicolor is an excellent Accent for a Water Garden or Stormwater Detention Basin. Small Groups or Masses of plants can provide Attractive Foliage, showy Spring Flowers, Cut Flowers and Erosion Control to wet sunny sites. This species is a valuable component of Cottage Gardens, Deer Resistant Plantings, Low Maintenance Plantings, Perennial Borders, Rain Gardens, Wetlands and Wildlife Gardens.

COMPANION & UNDERSTUDY PLANTS: Iris versicolor mingles cheerfully with Asclepias incarnata, Carex muskingumensis, Chelone glabra, Eupatorium perfoliatum, Osmunda cinnamomea and Rhexia virginica.

TRIVIA: Flowers are visited by butterflies and are very attractive to hummingbirds.

Iris virginica is a similar species that occurs in wetlands in the southern part of the Iris versicolor range. Iris virginica is shorter (to 2’) with leaves that often flop on the ground or in the water.

Iris versicolor is the provincial flower of Quebec.

The common name “flag” comes from a Middle English word (flagge) that means rush or reed. The specific epithet veriscolor means having various colors and refers to the different colored markings of the flower.

Harlequin blue flag (Iris versicolor), our floral emblem

Looking for a lovely lady for your garden?

This plant has loads of charm and doesn’t hide it. Bees find it attractive too, and are frequent visitors. It is just as beautiful as the other members of its family, and is becoming more popular all the time.

It is also the official floral emblem of Québec.

So it’s worth getting to know and to recognize!

Biological details

Harlequin Blue flag (Iris versicolor L.) is a superb rhizomatous perennial that grows in damp sites (ditches, swamps, riverbanks, edges of peat bogs, etc.). In Canada it can be found from Manitoba to Newfoundland. It also grows in a number of eastern US states. It forms dense colonies and its violet-blue flowers put on a show in June-July that we love to see, year after year.

Its long, stiff, erect leaves are sword shaped. From their base rises the stem bearing several flowers, each measuring 5 to 7 cm.

Its unusual flower parts give it an intriguing personality. The three sepals are the most colourful parts. They are violet marbled with white, yellow and green and heavily veined with dark purple. Narrow and horizontal at the base, they abruptly widen out into an elegantly arched triangular section. The three violet petals, only half as long as the sepals, are erect and alternate with the sepals. The reproductive parts are also rather odd. The style of the pistil is divided into three petal-like branches that arch over the narrow part of the sepals. The wide, bilabial end is erect. At its base is the stigma that receives the pollen. This position between each of the styles and the sepals forms a tunnel leading to the stamens and hence to the nectar.

Of course nectar attracts insects – in this case, bees. The veins on the sepals are thought to lead them toward the nectar they are seeking. A bee enters the tunnel and rubs up against the stamen loaded with pollen as it searches for food. As it backs out of the tunnel, the pollen it has picked up is normally not rubbed off on the outward-facing stigmatic lobe. When the bee enters the tunnel of another blue flag, the pollen sticks to that plant’s stigmatic lobe, and pollination occurs. This process improves the chances of cross-pollination and leads to greater genetic variety.

A controversial floral emblem

As ridiculous as it might seem, until recently we were the only Canadian province without a native plant as its floral emblem. An absurd mix-up led to our official floral emblem being the Madonna lily (Lilium candidum L.), which grows naturally in the eastern Mediterranean!

Ethnobiologist Jacques Rousseau, who succeeded Marie-Victorin as head of the Jardin botanique de Montréal, declared that the choice of the Madonna lily was as ridiculous as if we had picked the camel as Quebec’s animal emblem!

The stylized flower on the Quebec flag is certainly not a lily. It is probably styled after the yellow flag (Iris pseudacorus L.) found in abundance along the banks of the Lys river in Belgium – where it was likely known as the fleur dela Lys and contracted to fleur de lys. The fleur de lys, or lis, adorned the royal coat of arms of France. Perhaps the symbol on our flag should be described as a fleur d’iris instead of a fleur de lis!

The unfortunate thing for our blue flag, the unofficial emblem of the province up until 1999, is that it actually took a piece of legislation to make it official. Ever since Bill 38 (now known as E-5) was adopted by the National Assembly on January 23, 1963, tremendous pressure had been exerted on the Quebec government to correct this mistake. When Montréal hosted the Floralies internationales in 1980, Pierre Bourque, the Jardin botanique de Montréal’s Director at the time, chose the blue flag as the symbol of this exceptional horticultural event.

The Quebec government finally adopted Bill 49 (which became An Act respecting the flag and emblems of Québec) unanimously in the fall of 1999 (adopted on October 28 and received royal sanction on November 5, 1999), making the blue flag its official emblem.

Now it is up to us, as botanist Gisèle Lamoureux of Fleurbec says, to take care of this plant and protect it in its habitat. This means it mustn’t be dug up and sold! We have to encourage growers to produce it from seeds, as this can be done easily and quickly.

We can also encourage Quebeckers to look for hybrids of the versicolor and ensata species at nurseries, sold as Iris x versata, which are particularly well suited to home gardens.

Based on an article by Édith Morin in Quatre-Temps magazine, Vol. 16, No.4, and an article by Gisèle Lamoureux in FloraQuebeca magazine, Vol. 5, No.1.

Blue Flag Iris

Scientific Name: Iris versicolor
Other Common Names: blue wild iris, American fleur-de-lis, water flag
Blue flag grows from 60 to 90 centimetres tall at maturity. Several showy, purple-blue blooms appear from the end of May to early July. The flowers can be up to 10 cm across and have three showy sepals that gracefully curve down (or flop over, depending on your point of view). They have a splash of white and yellow near the centre and purple veins that probably guide pollinating insects to the food within. There are three paler petals nearer the centre, which are stiffly upright. Several large seeds are formed inside a large brown capsule. Blue flag leaves are long and lance-shaped, like prehistoric grass, sometimes up to 3 cm wide and 80 cm tall.
Similar Species: View below other Iris species

Photo Gallery:
(Please note — these photos are unverified images submitted by members of the CWF Photo Club.)

Range: Blue flag is our most widespread native iris. It is found from southern Manitoba eastward into the Atlantic provinces.
Habitat: The Blue flag grows in wet areas of woods and meadows and along shorelines of lakes, rivers and ponds — to the delight of cottagers and canoeists.
Primary Ecosystem Roles:

The blooms, containing nectar and pollen, attract pollinators such as hummingbirds, as well as bumblebees, butterflies, moths and other insects. Blue flag also serves as a source of shelter for animals that live along shorelines.

Article: Sarah Coulber
Photograph: Arlene and John Neilson

The iris has been admired for centuries. Mythologies of cultures from around the world refer to it. Modern-day interest in the iris is evident through its popularity in gardens everywhere and in the number of societies formed around this plant. There is even an iris on Quebec’s flag — the fleur-de-lis. Although supposedly a European species of iris, it seems many people now associate this symbol with the native blue flag iris.

Blue flag (Iris versicolor), also known as blue wild iris, American fleur-de-lis and water flag, is our most widespread native iris. It is found from southern Manitoba eastward into the Atlantic provinces. It grows in wet areas of woods and meadows and along shorelines of lakes, rivers and ponds — to the delight of cottagers and canoeists.

Under the right conditions, this iris can also be planted in an ordinary garden to lend an air of elegance. Because it is less attractive to deer than many other plants, it is a relatively safe addition for country gardens as well.


Although the rhizomes of blue flag are highly toxic, Aboriginal people have used the plant to alleviate a wide variety of ailments, including vomiting and constipation. The leaves have also been used for weaving baskets and mats, according to authors Doug Bennet and Tim Tiner in their book Up North Again.

(Caution: We do not recommend the use of these plants for medicinal or food purposes. Many plants are poisonous or harmful if eaten or used externally. The information on food and medicinal value is included only for interest. This information has been gathered from books and its accuracy has not been tested.)


Blue flag is a perennial that spreads by its fleshy rhizomes. You can divide it in the fall to speed up the process or to share it with a friend. You can also start new plants by seed — sow them in the autumn and cover with about 1 cm of soil. If successful, you will see shoots in the spring and flowering plants the following year. You can also start the seeds indoors at the end of winter. Keep the seeds in the freezer for a few weeks before planting and, in the spring, gradually harden off the seedlings in either a cold frame or another sheltered spot.


Grow blue flag in sun or partial shade and keep its roots moist by placing it in a damp area or a well-mulched garden or submerging it in the shallows of a pond.

Some Other Canadian Species

Western blue flag (Iris missouriensis)

  • Native to: southeastern British Columbia and southwestern Alberta
  • Habitat: moist areas, meadows, slopes, prefers sun and moist soil
  • Appearance: blue flowers atop stems that can reach 45 cm
  • Note: species at risk, ensure that it isn’t collected from the wild

Virginia blue flag (Iris virginica)

  • Native to: Ontario and southwestern Quebec
  • Habitat: marshes, shallow water, preferring sun or partial shade and wet feet
  • Appearance: blue flowers atop stems that reach 60 to 90 cm

Beachhead iris, wild flag (Iris setosa)

  • Native to: northwestern British Columbia, southwestern Yukon, Quebec, Newfoundland and Labrador, New Brunswick, Prince Edward Island, Nova Scotia
  • Habitat: upper beaches, dunes
  • Appearance: blue-purple or sometimes whitish flowers atop a stem that grows to 45 cm

Yellow iris is part of the extensive Iridaceae family, and is among those that have the highest water needs of all.

A few yellow iris facts

Name – Iris pseudacorus
Family – Iridaceae
Type – bulb flower, rhizome perennial

Height – 8 to 36 inches (20 to 90 cm)
Exposure – full sun, part sun
Soil – ordinary

Flowering – January to July depending on the variety

It simply loves dabbling in water and adapts particularly well to decorating the side of ponds, marshes, brooks and other bodies of water.

  • Read also: advice on caring for iris

Planting yellow iris

The best period for planting yellow iris is spring or summer, usually from May to November for the plants to bloom in the following summer.

  • Plant the yellow iris rhizomes directly in shallow water.
  • Simply immerse each yellow iris pot.
  • Keep it shallow, since putting it too deep would keep it from flowering. 15 to 20 inches (40 to 50 cm) is too deep already.
  • Keep sufficient spacing of about 2 to 4 inches (5 to 10 cm) between neighboring plants.
  • Go for sunny locations even though this plant tolerates part sun.

Pruning and caring for yellow iris

Caring for yellow iris can really become only the occasional check, because this is a flower that requires very little work.

  • Remove wilted flowers as they die off, but keep the leaves until the very end of their complete yellowing, usually until fall.
    Yellow iris leaves must be kept connected to the roots until they’re dead for the plant to build up its stocks for the following blooming.
  • Yellow iris must constantly have water, because it can’t cope with even the slightest dry spell.

All there is to know about yellow iris

Native to Europe, it is also found in Asia and North Africa, always in marshy wetlands. It thrives near ponds, along running water, both in plains and in lower mountain ranges.

Yellow iris is a hardy plant that survives winter very well.

Cold actually conditions part of the plant’s growth.

Three magnificent yellow petals form the flower.

Smart tip about yellow iris

The lifespan of an iris can reach anywhere from 5 to 20 years.

To ensure it lasts a generation, offer it bulb-plant organic fertilizer every year after the blooming.

  • Read also: advice on caring for iris

How and where to grow Yellow Flag Iris, Iris Pseudacorus

Yellow Flag Iris

Yellow Flag Iris (Iris Pseudacorus)

This is striking attractive tall plant found in wet woods and by the edges of Ponds, Streams and ditches.

It has large, bright flowers and long leaves. It is a perfect plant to put by the waters edge in a garden. It will, once established, survive in water up to 15 cm in depth. The large flowers are attractive to honey bees and hoverflies. The nectar has a strong attractive scent.

Anyone with a pond or water in their garden should think about introducing Yellow Flag Iris. They are best grown from plugs. Whilst they will grow in semi shade they perform best in full sun to get the maximum bloom

It can spread naturally once established by underground rhizomes.

It will grow to height of about 1.5 to 5 feet. Whilst it can be grow from seed the best results come from planting plug plants between October and April. If you have some already growing then the existing rhizome can be taken in Spring or Autumn and planted out in wet ground

Yellow Flag Iris Plugs

Gorgeous yellow iris is ecological threat to PNW wetlands

In Oregon, yellow flag blooms in late spring or early summer. Several flowers can occur on each stem, along with one or two leafy bracts. Each flower resembles a common garden iris with three large (1.5- to 3-inch) downward facing yellow sepals and three smaller upward pointing petals. The yellow sepals are often streaked with brown to purple lines. Flower color ranges from cream to bright yellow. Some horticultural varieties have been developed with variegated leaf color. The plants may grow to almost five feet in height. The leaves are mostly basal and are folded and clasp the stem at the base in a fan-like fashion.

A perennial, yellow flag iris will remain green during the winter where the weather is mild, but leaves will die back during periods of prolonged drought or below-freezing temperatures. It spreads both by seed and by stout underground stems called rhizomes from which its roots can grow to a foot in length.

After flowering, the large seed capsules of yellow iris are up to 2.5 inches long and contain many dark to reddish-brown seeds. When not flowering, yellow flag iris may be confused with cattail (Typha latifolia) or broad-fruited bur-reed (Sparganium eurycarpum). Look for the fruits in the summer, or the fan-shaped plant-base at other times of year.

Up to several hundred flowering plants may be connected by rhizomes. Fragments of rhizome can form new plants if they break off and drift to suitable habitat. The flowers are pollinated by bumblebees and long-tongued flies. Seeds germinate and grow well after being burned in late summer. Yellow flag readily resprouts from rhizomes after burning.

As a popular ornamental plant for wet areas or well-mulched soil, yellow flag is widely sold in nurseries and on the Web. It has often been planted in wastewater or storm water treatment ponds, been used to control erosion and is known to take up metals and nutrients in wastewater treatment facilities. It is a popular garden plant for wet or well-mulched soil, and has been introduced as an ornamental throughout the world.

“Yellow flag is being widely distributed by water garden enthusiasts,” said Hulting. “This likely leads to unintentional releases in urban and suburban wetlands and eventually wetlands across the landscape, spread by seed and rhizome fragments during high water events. We’d like to help gardeners become more aware of the ecological effects invasive plants like yellow iris might have on the environment.”

The best control is prevention, said Hulting. “Learn to identify it and don’t plant it. Encourage other gardeners not to plant it.”

Yellow flag is listed on the Oregon Department of Agriculture’s Noxious B list, meaning it is locally invasive and not yet widespread. The Pacific Northwest Exotic Pest Plant Council lists it as ‘A-2 Most Invasive-Regional’ (highly to moderately invasive but still with a potential to spread).

The OSU Extension Service recommends the following wetland native plants as being more ecologically appropriate alternatives to yellow flag: monkey flower, Rocky Mountain iris, Douglas iris and skunk cabbage. Also, these non-native ornamentals are less invasive: Japanese iris, Siberian iris and blue flag.

To help home gardeners and landscape designers make sound ecological choices about what to plant in their gardens, the Oregon State University Extension Service has published a 52-page booklet called GardenSmart Oregon (EC 1620), in cooperation with City of Portland, The Nature Conservancy, Oregon Association of Nurseries, Clackamas Community College, Oregon Public Broadcasting, OSU Extension Service and OSU Sea Grant. GardenSmart Oregon is available online; or, call 1-800-561-6719 to request a printed copy of GardenSmart Oregon ($3 per copy shipping and handling fee). Local county offices of the OSU Extension Service have copies available for no charge.

Pulling can control isolated plants of yellow flag iris or digging, but use care and protect your skin as resins in the leaves and rhizomes can cause irritation. Because rhizome fragments can grow to form new plants, be sure to clean up all fragments. Large-scale tillage to control yellow flag should be avoided because of the likelihood of spreading rhizome fragments, warned Hulting.

“Limiting soil disturbance can help native plants survive and make the site more resilient to reinvasion by yellow flag,” he said.

If you can do nothing else, remove and destroy the seed heads and flowers of yellow flag, he advised.

Large-scale infestations of yellow flag most likely need to be managed by chemical means to achieve complete control and limit the spread. Formulations of glyphosate labeled for aquatic uses (examples: Rodeo or Aquamaster) have been effective on yellow flag iris when applied as a spot treatment. Take care to not overspray onto desirable plants when making glyphosate applications. Follow the mixing directions and application instructions on each label.

“Cut stump” treatments, or cutting or mowing foliage and applying glyphosate directly to the cut surface of individual plants have also been effective for managing smaller infestations of yellow flag iris and can negate herbicide injury to non-target plants. Because this plant is a rhizomatous perennial multiple applications over multiple years will likely be needed for complete control, said Hulting.

No biological control organisms have been approved for yellow flag iris.

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