Description & Overview

Harlequin Blue Flag Iris is a Wisconsin native, clump-forming iris that you typically encounter in wet prairies, marshes, fens, stream banks, ditches, and shorelines. In May, flower stalks bear 3 to 5 showy, rich violet-blue flowers that are 3″ to 4″ in length. Though rare, flowers can be white, giving rise to the plants’ botanical name. Greenish-gray lanceolate leaves make an appearance in spring, setting the stage for the main attraction – those blooms! May also be known as Large Blueflag, Northern Blueflag, and Harlequin Blueflag.

Core Characteristics

Category: Perennial

Wisconsin Native: Yes

USDA Hardiness Zone: to zone 3

Mature Height: 2-3 feet

Mature Spread: 2-2.5 feet

Growth Rate: Moderate

Growth Form: Perennial, spreads via self-seeding and radially via rhizomes

Light Requirements: Full Sun

Site Requirements: Wet, organic soils in full sun. Adaptable to a wide variety of soil types.

Flower: Violet-blue with a splotch of yellow

Bloom Period: Late May - June

Foliage: Green-gray, sword-like foliage emerge in Spring. Leaves are usually shorter or similar in height to the flower.

Fall Color: Yellow-brown, not showy

Urban Approved: No

Fruit Notes: 1.5" long capsule containing shiny black seeds. Capsules often persist over winter.

Suggested Uses

Shoreline stabilization
Root mass of established colonies are great at protecting shoreline, can tolerate mildly brackish water, and permanent inundation up to 6″.

Wetland restoration
Blueflag Iris can add diversity and color to any wetland restoration project. To combat the negative effects of stormwater runoff, it’s important to cultivate a vegetative buffer around the wetland area. This buffer assists in filtering excess nutrient runoff – notably phosphorus and nitrogen, and slowing water flows after typical rain events.

Rain Garden
Whether the garden is in your backyard, outside your office, or at a nature center, Harlequin Blue Flag Iris can be a great addition that also enhances water quality and reduces run-off. Best in rain gardens that maintain a consistent or persistent level of moisture.

Harlequin Blue Flag Iris is a Wisconsin native, clump-forming iris that you typically encounter in wet prairies, marshes, fens, stream banks, ditches,…
Harlequin Blue Flag Iris is a Wisconsin native, clump-forming iris that you typically encounter in wet prairies, marshes, fens, stream banks, ditches,…

Wildlife Value

Ruby-throated Hummingbirds, skippers, and short-tongued bees are all visitors of Large Blueflags. The conspicuous markings on the flower petals dictate bees as the primary pollinators. Irises have a unique inflorescence; they have 3 drooping sepals called “falls”, and 3 smaller upright sepals called “standards”. Iris versicolor has both falls and standards that are typically violet-blue, while only the falls have a splotch of yellow at the base. Bees use the falls as a landing pad, with the purple veining and yellow markings guiding them to the nectar glands.

Maintenance Tips

As with most native plantings, Large Blueflag doesn’t need additional fertilizers when cited properly in the landscape – all-around better for the environment! Division of clumps is best performed in July/August; once broken, the roots exude a sap that can be irritating to the skin, so be sure to wear gloves.

Harlequin Blue Flag Iris is a Wisconsin native, clump-forming iris that you typically encounter in wet prairies, marshes, fens, stream banks, ditches,…

Pests/Problems

To obtain the full wetland benefits this plant offers, allow old vegetation to persist through winter. This will create a barrier that will discourage any unwanted visitors such as nesting geese in very early Spring. If desired, after fall frost has set in, any desiccated leaves can be cut back to about 1″ above the crown.

Root stocks (corms) may be fed upon by aquatic rodents, such as beaver, muskrat, and groundhogs. Snails may eat the foliage. Various rots can occur, such as rhizome rot, crown rot, and bacterial soft rot. Susceptible to Iris borer, Iris thrips, and aphids. Aphids can transmit the mosaic virus. Be sure to sterilize your pruners after every cut.

Deer problems in your area? Iris is one plant that they leave alone, likely due to its unpalatability.

Leaf Lore

Its specific epithet, versicolor, is derived from the plant’s ability to produce many-colored blooms while the common name, ‘flag’, comes from an old English word flagge for reeds and refers to its natural preference to wetlands. The genus Iris comes from the Greek word meaning ‘rainbow’.

It’s also thought that the fleur-de-lis resembles the Iris flower with 3 petals tied with a band.

The entire plant (leaves, corms, flowers) is poisonous, especially the roots. Nevertheless, Indigenous Americans medicinally used Large Blueflag on burns, swellings, sores, and liver and kidney disease.

Companion Plants

Native plants that compliment site conditions:
Swamp Milkweed (Asclepias incarnata), Spotted Joe-Pye Weed (Eutrochium maculatum), Marsh Marigold (Caltha palustris), Ironweed (Vernonia fasciculata), Halberd-leaf Mallow/Rose Mallow (Hibiscus laevis), Common Ninebark (Physocarpus opulifolius), Buttonbush (Cephalanthus occidentalis), American Elderberry (Sambucus canadensis), and Cardinal Flower (Lobelia cardinalis)

Plants that compliment color/bloom-time:
Wild Bergamot (Monarda fistulosa), Common Spiderwort (Tradescantia ohiensis), Culvers Root (Veronicastrum virginicum), Wild Geranium (Geranium maculatum), False Indigos (Baptisia spp.), Nodding Pink Onion (Allium cernuum), Amsonia (Amsonia spp.), Pinks (Dianthus spp.).

Harlequin Blue Flag Iris is a Wisconsin native, clump-forming iris that you typically encounter in wet prairies, marshes, fens, stream banks, ditches,…
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Written by Beth DeLain