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Iris virginica Virginia Iris, Blue Flag, Blue Flag Iris

Edward F. Gilman, Ryan W. Klein, and Gail Hansen

Introduction

Blue flag iris has wonderfully textured, light-green foliage emerging directly from the ground in dense clumps. It grows 12 to 18 inches tall, producing lavender-blue flowers about 4 inches across in the spring. Flowers are displayed in a showy fashion slightly above the foliage. They are native to boggy areas where water stands all year long. They will grow in standing water.

Full Form - Iris virginica: Blue flag, blue flag iris.
Figure 1. Full Form - Iris virginica: Blue flag, blue flag iris.
Credit: Edward F. Gilman, UF/IFAS

 

Full Form - Iris virginica: Blue flag, blue flag iris.
Figure 2. Flower - Iris virginica: Blue flag, blue flag iris.
Credit: Edward F. Gilman, UF/IFAS

General Information

Scientific name: Iris virginica

Pronunciation: EYE-riss vur-JIN-nick-uh

Common name(s): Virginia iris, blue flag, blue flag iris

Family: Iridaceae

Plant type: herbaceous; ornamental grass; aquatic plant

USDA hardiness zones: 8B through 11 (Figure 3)

Planting month for zone 8: year-round

Planting month for zone 9: year-round

Planting month for zone 10 and 11: year-round

Origin: native to Florida

Invasive potential: aggressive, spreading plant

Uses: border; mass planting; container or above-ground planter; naturalizing; water garden; accent

Availability: somewhat available, may have to go out of the region to find the plant

Shaded area represents potential planting range.
Figure 3. Shaded area represents potential planting range.
Credit:

Description

Height: 4 to 7 feet

Spread: 1 to 3 feet

Plant habit: upright

Plant density: moderate

Growth rate: moderate

Texture: coarse

Foliage

Leaf arrangement: most emerge from the soil, usually without a stem

Leaf type: simple

Leaf margin: entire

Leaf shape: linear

Leaf venation: parallel

Leaf type and persistence: evergreen

Leaf blade length: 18 to 36 inches

Leaf color: green

Fall color: no fall color change

Fall characteristic: not showy

Flower

Flower color: blue

Flower characteristic: spring flowering

Fruit

Fruit shape: elongated

Fruit length: 0.5 to 1 inch

Fruit cover: dry or hard

Fruit color: green

Fruit characteristic: persists on the plant

Trunk and Branches

Trunk/bark/branches: typically, multi-trunked or clumping stems

Current year stem/twig color: not applicable

Current year stem/twig thickness: not applicable

Culture

Light requirement: plant grows in part shade/part sun

Soil tolerances: extended flooding; slightly alkaline; clay; sand; acidic; loam

Drought tolerance: moderate

Soil salt tolerances: poor

Plant spacing: 24 to 36 inches

Other

Roots: not applicable

Winter interest: no special winter interest

Outstanding plant: not particularly outstanding

Pest resistance: long-term health usually not affected by pests

Use and Management

The plant is grown and used for its foliage effect as well as the flower display. The plant flowers for a short period in the spring but the coarse-textured, upright foliage makes this a year-round favorite for a wet garden spot. It is well suited for planting in mass in front of a shrub border, or as a tall ground cover. On 2-foot centers, a thick ground cover can be formed in about 2 years. The individual plants will be nearly indistinguishable by that time.

Although full sun is tolerated if soils stay moist, a well-drained, partially shaded location provides the best habitat for Iris. Plants can be allowed to dry out slightly in a shaded location with little damage to foliage or flowers. As with other irises, over-fertilization will encourage foliage growth at the expense of flowers. A light application once each year should be enough to maintain good growth and a reliable flower display.

Pests and Diseases

No major pest or diseases problems are usually encountered on this iris.

Publication #FPS-288

Release Date:February 12, 2024

Related Collections

Part of Shrubs Fact Sheets

Related Topics

  • Critical Issue: Agricultural and Food Systems
Organism ID

About this Publication

This document is FPS-288, one of a series of the Department of Environmental Horticulture, UF/IFAS Extension. Original publication date October 1999. Revised October 2023. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication.

About the Authors

Edward F. Gilman, professor emeritus; Ryan W. Klein, assistant professor, arboriculture; and Gail Hansen, professor, sustainable landscape design; Department of Environmental Horticulture, UF/IFAS Extension, Gainesville, FL 32611.

Contacts

  • Gail Hansen de Chapman
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