This plant family includes close to 300 species that are found across the northern hemisphere in such diverse ecosystems as bogs, mountain screes, meadows, and almost desert-like conditions. Add to that the cultivars of popular species such German Bearded Iris (Iris germanica), which exceed 30,000, and you have a nearly limitless choice of colour and form. Then we have the broad seasonality of bloom, with Iris reticulata and I. danfordiae flowering late winter to spring, followed by Siberian and Japanese Iris (I. sibirica / I. ensata), from mid-spring to early summer, and finishing with the late summer to fall flower display of repeat-blooming German Bearded Iris; so, you can have one in flower in your garden at almost any time of the year.
The pinnacle of the Iris world is the elegant German Bearded Iris with their large blooms which are often two-tone, with different coloured standards and falls (lower flower portion) such as ‘Mexican Holiday’ (orange/bronze) or ‘Edith Wolford’ (soft yellow/purple). There are also picotee forms or those with brightly coloured edges which include ‘Rare Treat’ and ‘Cinnamon Girl’. The rather bland looking near-white ‘Florentina’ has actually been the source of Orris root since ancient Egypt, with the violet-scented rhizomes (after being dried for 2 years) being used to enhance perfumes or in more modern times, flavour gin. This species requires well-drained soil with at least 6 hours of sun in summer and should be divided every 3-4 years from late July into August. Allow the cuts on the divisions to dry overnight and plant with the top of the rhizome sitting just above the soil surface. Last but not least, try to avoid high nitrogen fertilizers as this will produce lush foliage that is prone to fungal problems. Flowering time is from late spring into early summer, with repeat bloomers continuing through the summer into early fall.
Iris sibirica or Siberian Iris are probably the second most popular, with their erect grass-like foliage and abundant flowers, albeit smaller than the German Bearded. The colour range is from deep purple (‘Ruffled Velvet’) to violet-blue (‘Caesar’s Brother’) to white (‘White Swirl’) to yellow bicolors (‘Butter and Sugar’), with some bearing intricate veining (‘Persimmon’), and all are extremely cold-hardy at USDA zone 2. Heights vary from 12-16” right up to 40” tall and they prefer evenly moist soils that do not dry out. They bloom from late spring to early summer, usually just after the tall bearded Iris and before the Japanese, and make excellent cut flowers. Divide clumps in early spring or late summer, using the method shown at the end of this article, when a prominent hollow starts showing in the center of the plant.
There are numerous Iris species that adapt well to bogs or even use as shallow marginals in ponds. These include Iris louisiana, Blue Flag (Iris versicolor) and of course the very showy Iris ensata or Japanese Iris. The only species you should be avoiding is the Yellow Flag Iris (Iris pseudacorus) which was introduced from Europe and has become an invasive plant in our wetlands. The showiest of these aquatic species is definitely I. ensata, with the Dinnerplate Series (such as ‘Tiramisu’) having blooms up to 6” across.
Iris can even be used as foliage plants with the gold (‘Aurea Variegata’) and silver variegated (‘Argentea Variegata’) Iris pallida holding up well as an ornamental even after the fragrant pale purple blossoms have faded. The tiny Arctic Iris (Iris setosa var arctica) works well in the rock garden as it forms a grassy tuft (6-12” tall) covered in lavender-blue flowers from late spring into early summer. Two rarities worth looking for are the fragrant Iris bucharica and the more tender and shade loving (Zone 7) Iris japonica with its fringed blooms of white with intricate blue and yellow markings.
Last but not least on my abbreviated overview are the bulbous Iris, which include the early blooming Iris reticulata (‘J.S.Dijt’, ‘Eyecatcher’, ‘Harmony’) and I. danfordiae, as well as the early summer-flowering Dutch Iris (Iris x hollandica), which are also excellent cut flowers. These are available as bulbs in the fall or forced plants in early spring.
Dividing Siberian Iris*
Tools – You will need a sharp spade (tapered or blunt-nosed) and an old serrated bread knife.
Step 1 – Dig up the entire clump by cutting around the plant with the spade, and leveraging it out of the ground.
Step 2 – Gently knock off the excess soil.
Step 3 – Use the serrated bread knife to cut a division from the band of vigorous growth on the outside edges.
Step 4 – Lightly root prune the new division and replant immediately with some fresh soil. When dividing in late summer, cut the foliage back to 6-8”.