If you like spring color that reminds you of a Monet painting but you don’t want a lot of fuss, give Siberian iris a try. Although they’re not really from Siberia, they’re hardy to Zone 3 and will survive almost anything Iowa can throw at them.
What are Siberian Irises?
Siberians are rhizomatous perennials that grow in a clump and produce one or more stalks of beardless blooms in early-mid spring. Bloom stalks reach to 3 feet above narrow, grass-like green or green-blue foliage that grows around 2 feet tall. Even after blooms are gone, the vase-shaped clumps sway in the breeze, offering visual interest all season.
Each flower stem bears two to five blossoms in shades of blue, purple, lavender, white, yellow, pink, wine, and bi-colors. The original Siberians were mostly purple, but modern hybridizers have expanded to palette to virtually every color except true red.
Siberians grow from underground creeping rhizomes that will spread to form impressive clumps that can remain undisturbed for several years until they show signs of crowding.
Siberian Iris Culture: How to Grow
Unlike their glamorous cousins, the bearded iris, Siberians are easy to grow if given 6-8 hours sunlight and humus-enriched soil that remains moderately moist. While they will grow near water, they won’t survive if roots are submerged. Whether you’re starting a new bed or re-making an old one, it’s best to loosen the soil 6-8 inches down. Siberians grow best in slightly acid soil (pH 5.5 to 6.9); since Iowa soils are alkaline, it’s best to incorporate peat moss, compost, or some sort of
humus to lower the pH. (If in doubt, have your soil tested.)
At planting time, you can incorporate a bit of soil sulfur. Best time to start Siberians is early spring or mid-summer. If you’ve received bare-root plants in the mail, soak the rhizomes in water overnight. Next day, plant the rhizomes 1-2 inches deep, mulch, and keep watered for the remainder of the season. In subsequent years, keep the soil moist but not saturated.
A top dressing of organic mulch (shredded bark, pine needles, etc.) will do the trick. Do not fertilize the first year. In subsequent years, you can use an acid fertilizer as for azaleas. Provide winter mulch. If the plants have bloomed, remove bloom stalks after
flowering in order to direct all the plant’s energy toward next year’s growth. If you are remaking an old bed, dig up the rhizomes, divide as needed, discarding old or diseased rhizomes (see below), then plant as outlined above.
Pests and Diseases
Siberians are remarkably free from disease. Aside from dry soil, Siberian iris’s worst pest is iris borer. While some believe iris borer does not attack Siberians—they’re wrong. If you see that plants are deteriorating or have stopped blooming, dig up and
inspect the crown of the plant (where roots meet foliage). If you see a fat, pink worm, remove it, cut away any rot, and replant immediately. To discourage future attacks, keep the area clean of weeds and other debris, avoid overcrowding, and keep the area
Modern Siberians are hybridized from species hailing from eastern Europe, north eastern Turkey and Russia, and the Caucuses—with others from Japan and Korea. With a background like this, you know they’re tough! Just give them sun, moderately acid soil, enough moisture—and they’ll reward you with lovely blooms every year.