Wednesday, April 24, 2013

Native Species Profile - Northern Blue Flag Iris

Northern Blue Flag Iris (Iris versicolor)

Northern Blue Flag Iris (Iris versicolor) is 2 to 3 foot tall wetland plant with sword-like leaves and  violet/blue flowers trimmed with yellow and white.  The leaves form a flattened fan-like cluster.  The plant spreads both by seed and by spreading rhizomes.  Northern Blue Flag often forms dense colonies.

A small colony of Northern Blue Flag in a Mixed Hardwood-Conifer Swamp
The 2 to 3.5 inch wide flower appears to have six petals, but the larger veined "petals" are actually sepals - the smaller petals stand erect and are less showy than the sepals.  On most flowers the sepals are green and clasp the base of the flower.  The sepals on the Northern Blue Flag Iris are actually the showiest part of the flower.  The yellow centers and dark purple veins act as nectar guides. 

As I explained in my post about the Spring Beauty (Claytonia virginica), bees (and many other insects) have the capability to see ultraviolet light.  Under UV light these lines are like a signpost pointing the way to the available nectar.  These nectar guides contrast with yellow center of the sepal further advertising the source of nectar. This feature is is found in many flowers that are pollinated primarily by bees.  As the bee follows the nectar guides on the Northern Blue Flag it brushes past the pistil, thus transferring pollen from a different plant and cross-pollinating the flower, and then the stamen to pick up pollen to transfer to another flower.
Petals (yellow arrow) and sepals (red arrow)- note the deep purple nectar guides on the sepals.

The Northern Blue Flag Iris is found in eighteen northeastern states and eight eastern Canadian provinces.  It is found is a variety of wetland habitats including swamps, marshes, shorelines, wet meadows, and some wet prairies.  It can be found both is bright sunlight and deep shade.  It typically flowers between May and July.

Northern Blue Flag Iris along the edge of a marsh

A Northern Blue Flag Iris surrounded by broad-leaf wetland plants in a deciduous swamp

Basic Information

Blue Flag Iris 
Iris versicolor

Height: 2-3’ tall

Habitat:  wet, sun or shade, meadows, marshes, edges of wetlands, lakes, and rivers

Flower Color:  blue or violet, trimmed with yellow

Bloom Time:  May – July

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