Siberian irises are the most maintenance-free species of the iris family. In our area, they typically bloom in late May and early June. Siberian irises can be identified by the fact they have smooth, thin, grass-like leaves without a distinct rib that runs lengthwise down the middle and no beards on their flowers. Although similar looking, the Japanese iris does have a distinct mid-rib on its leaves. Siberian irises are very adaptable to site conditions as they prefer sun but will tolerate part shade; are not fussy about soil types; will tolerate a wide range of conditions; quickly form large clumps; are resistant to iris borers and are drought tolerant once established. While they are not water loving like the Japanese type, they will tolerate wetter soils therefore they can also be used beside pools or bogs.
The Siberian iris begins to bloom in that gorgeous period of mid- to late-spring when bearded iris, peonies, alliums, oriental poppies and foxgloves are also flowering. The plants grow ¾ to one metre and can be presented as a backdrop, border or focal plant. They maintain their beautiful grass-like foliage all season. After blooming if you chose not to deadhead the spent flower, the mature seed pod and stem are excellent in dried flower arrangements. The foliage starts to turn yellow in the fall once you receive frost in the evenings.
Iris flowers are composed of 6 segments. The inner 3 upright segments are the true petals and are referred to as standards. The drooping, outer 3 segments are petal-like sepals and are known as falls. The flowers of Siberian irises are smaller and more delicate than those of bearded irises and unlike bearded irises, their falls do not have fuzzy growths or beards. Like other irises, these plants grow from rhizomes – a type of horizontal underground root stock from which shoots grow upward and roots descend. The preferred time for planting Siberians is late September when you can buy packaged rhizomes from the nurseries, but most nurseries will have potted plants available in the growing season. Space plants about forty to sixty centimetres apart. For the best visual display, plant 3, 5, or more of the same variety in a clump. To aid in good establishment water Siberian irises generously for at least one full growing season. Plants seldom bloom the first year after planting but should bloom well by the third or fourth year. They will eventually form large, well-established clumps.
Once established, Siberian irises don’t require a great deal of care. If possible, water once a week during hot, dry weather. Cut back the dead debris in late fall or early spring. Be sure that the clump is kept free of weeds, otherwise, grasses (particularly crabgrass) may get a foothold right in the midst of a clump, pass unnoticed for a time and easily become so firmly entrenched that it is hard to remove them without mutilating the clump. To help older clumps maintain their vigorous growth, a top-dressing of compost and manure may be applied in the spring or after flowering. Do not use lime or bone meal, as Siberians prefer a neutral or slightly acidic environment. You don’t need to divide the clumps until you start getting fewer flowers.
Siberians resent being moved and if the subdivisions are too small, they require considerable time to become established and may not bloom until the second or third year after planting. When planting Siberian irises, always keep in mind that they show off to better advantage if left undisturbed for five or six years, so be careful to select the best spot for them before planting.
In the past, very little hybridizing had been done with Siberian irises, but in recent years there have been some spectacular new varieties introduced. Here is list of some great varieties I either have myself or deem as good to try.
- Butter and Sugar-white standards, yellow falls.
- Caesar’s Brother-dark purple flowers.
- Eric the Red-dark wine-red flowers.
- Flight of Butterflies-violet-blue standards, white falls with butterfly-wing pattern of violet-blue veins.
- Jeweled Crown-deep wine-red flowers, falls have large circular gold blaze which fades to white.
- King of Kings-large white flowers.
- Lady Vanessa-light wine-red standards, ruffled medium wine-red falls.
- Orville Fay-medium blue with darker blue veins.
- Pink Haze-pink-lavender flowers.
- Ruffled Velvet-violet standards, darker falls.
- Savoir Faire-deep blue flowers.
- Snow Queen-white flowers.
- Sparkling Rose-rose-pink flowers.
- Spring’s Brook-blue-violet flowers.
- Super Ego-light blue standards, lighter falls.