Zone: 3 to 8
Soil: sand to loam
Light: Full sun to part sun
Bloom colour: Blue
Bloom period: Spring
Height: see notes
Moisture: see notes
Notes: When people think of irises, they are usually imagining the flowers depicted so beautifully by Monet. It may be hard to compete with German Iris, but our native species are still eye-catching and deserve a place in a wildlife garden if you can provide the correct conditions.
The flowers of Northern Blue Flag Iris are large yet full of intricate details. If you watch the interactions with bees, then you will notice that these atypical flowers have different entry and exit points. In most flowers, the sepals are green and inconspicuous. They protect the flower until it opens. In the Iris, the sepals are large and brightly coloured. Since the sepals droop downwards, they are called the falls. On each of the falls, you find a yellow signal that indicates where the bee should land and a conspicuous network of veins that may guide the bee towards the nectary.
The true petals are much smaller and point upwards; they are called the standards. Growing just above the each yellow signal is the stigmatic lip which is attached to the ovary in the centre of the flower by a long and showy style arm. The style arm should not be confused for a petal. When a bee lands on the signal, it pushes against the stigmatic lip and then passes underneath the style arm where the male reproductive part, the anther, is located. The sequencing is important because any bee will deposit pollen from other flowers before picking up pollen from this flower, thus preventing self-pollination. The bees continues towards the centre of the flower under the style arm where it can reach the nectary. It exits the flower sideways.
The two species that you might find in a garden in Ontario are Iris lacustris and Iris versicolor. Iris versicolor is similar Iris virginica while Iris lacustris is similar to Iris Cristata. Both of these similar species have a more southernly distribution.
Iris versicolor is quite common in Ontario. It grows about 3 feet high. The beardless flowers are appear at the end of spring and are attractive to bees. Whilst the individual flowers do not last that long, they continue to flower for about 3 weeksIt needs near constant moisture and a loamy soil to look its best. Naturally, it can be found in wet meadows and marshes.
Iris lacustris is a dwarf Crested Iris and has a rather limited distribution within the great lakes region. It only grows about 6 inches high but the flowers much larger than you would expect for a plant of that height. It interacts a bit differently with bees because it has a shorter style arm than Iris versicolor. The bees can reach the nectary more easily and reverse out of the stigmatic lip. The growing conditions of this species are quite different. They prefer sunny, sandy and well drained soil. They tolerate drought well.
Both of these plants can be grown in containers and they will fill in any empty spots as they spread by rhizomes. They are pure eye-candy and they are great for pollinators as well. I grow I. versicolor in a large container in combination with Water Avens.