Iris are popular additions to gardens for good reason. They are uniquely beautiful and easy to grow. Bright blue native iris are among my favorite spring wildflowers. Many early spring species including Anemones, Trillium, and bloodroot are structurally simple with petals and sepals surrounding a central pistil and a cluster of brightly colored stamens. Not so with our native Iris.
Floral Anatomy 101
Many wildflower books introduce us to floral vocabulary. The inner set of floral leaves are the corolla and usually called petals. The outer whorl of floral leaves are the calyx and usually called sepals. Taken as whole the showy portion of a flower is called a perianth. The perianth of our native Iris species have a unique and clever design, an architecture intended to attract and take advantage of visiting pollinators.
The corolla or inner whorl of 3 colorful petals of native Iris species are usually slender, more or less erect, and uniformly colored. They are called standards. The calyx, or outer whorl of floral leaves of an Iris are broad, arching, and very showy. They tend to descend, are appropriately called falls, and most have brightly colored patches called signals. In most species, falls are decorated with bright lines or markings which serve as pollinator nectar guides. Above each fall, an arching, petal-like style arm adds a third floral whorl and gives the entire blossom a sense of depth.
Take a good look at the below Iris verna blossom and note 3 unmarked blue standards and 3 brightly marked falls. Also note the 3 petal-like style arms with slightly reflexed tips above each fall.
In simple flowers, think tulips, the style is a slender stalk topped by an enlarged stigma. In Irises, the modified pistil is a broad, showy, petal-like style arm arching over a pollen producing stamen. Bees land on the fall, squeeze beneath the style arm to access the nectaries, brush their pollen-covered backs against a sticky stigmatic lip, gather pollen from the stamen, and emerge to fly off to the next blossom. A bit of native plant genius!
Despite significant difference in size and growth habit, the blossoms of each of the four native species discussed below look quite similar.
Iris verna , or “dwarf Iris”, grows to a height of 4″-6″. It is found in the mountains, the piedmont and the sandhills where it does well in recently burned areas. It is one of two southeast dwarf Iris species. Leaves are slender and falls are marked with bright orange patches without a curly crest. Iris verna does not form the dense, leafy clusters that are typical of Iris cristata. Iris verna is especially attractive when it emerges from a freshly burned longleaf pine forest floor.
Iris cristata, or “crested dwarf Iris” is more common at higher elevations where it grows in large, showy clusters. Note the wavy “crests” on white signals on the falls of this Iris. One of my favorite sightings in early spring is a bright blue patch of Iris cristata along the Blue Ridge Parkway or on a Great Smoky Mountain hiking trail. Both dwarf iris species are suitable for plant gardens but I might prefer crested Iris based on its showy, long-lasting foliage.
Iris virginica, or “blue flag Iris” can be stunning. It is tall, handsome, often grows in standing water, and is very attractive to bumblebees and butterflies. My favorite location for Iris virginica is Martin’s Lake in the Carolina Sandhills NWR. This Iris species is an excellent addition to a wetland garden or a pond margin.
In 2015, a patch of Trillium pusillum was found in the Pee Dee National Wildlife Refuge. In the spring of 2016 the wet pine tract where these Trillium were found was burned. When I returned a month or so after the burn, I found masses of tall, very slender Iris stems emerging in several wet areas Weeks later blossoms of the somewhat rare Iris prismatica (slender blue Iris) began to appear. While not as robust at Iris virginica, slender blue Iris is a charming wildflower and I am excited to revisit this species when it blooms this May.