The Siberian iris (I. sibirica) is beloved for its delicate flowers and soft, grasslike foliage. This lovely perennial is easier to grow than the bearded iris, needs very little care, and blooms from spring through early summer. Learn more about when to plant, divide, and grow the Siberian iris.
When you hear the word 鈥渋ris,鈥 do you see a big bearded beauty rising up above swordlike leaves? You鈥檙e thinking of the bearded iris (Iris germanica), a popular spring/summer garden star. The Siberian iris (I. sibirica), another flower entirely, is well worth your attention, too.
The Siberian iris generally grows 2 to 4 feet tall; withstands wind, rain, and cold; and makes a lovely cut flower.
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When Does Siberian Iris Bloom
Impressively, one mature plant can send out more than 20 stems of flowers at once, in a bloom season that lasts from late April to early summer. The Siberian iris quickly fills in spaces in a sunny border and works well at corners, too. Good companion plants are aquilegia, daisies, lupines, peonies, phlox, and pinks.
Best Conditions for Iris
The Siberian iris grows well in USDA Zones 2 to 9. In northern regions, grow it in full sun. It performs reasonably well in light shade where seasons are warm. In extremely hot southern climates, grow it in a shady location. Although it will tolerate dry periods, for best performance, plant it with perennials that you water well all summer long.
When to Plant Siberian Iris
Siberian irises are usually planted in the spring. Space plants about 18 to 24 inches apart. Plant rhizomes with the crowns 1 inch below the soil level and cover them with soil鈥2 inches deep, if the soil is sandy. To avoid air pockets beneath the crown, make a small hill of soil in the center of the planting hole, place the rhizome on the hill with the roots spread around it, fill the hole with soil, and pack it tight. I like to plant in groups of 3 or 5 or more for a beautiful display.
Keep evenly moist for 6 to 8 weeks after planting. Water once a week during hot, dry weather. Water when needed for at least one full growing season. Just note Siberian irises may not bloom the first year after planting but that they will eventually form large, well-established clumps.
When Do Siberian Iris Bloom
To have Siberian irises in bloom for the longest period of time, include both early and late varieties in your garden. Here are a few examples:
Early Bloomers:
- 鈥楤辞耻辩耻别迟鈥
- 鈥业苍诲测鈥
- 鈥楶leasures of May鈥
Late Bloomers:
- 鈥楰ing of Kings鈥
- 鈥楲颈产别谤迟测&苍产蝉辫;贬颈濒濒蝉鈥
When to Cut Back Siberian Iris
Remove spent flowers after they bloom to keep seed heads from forming. In late fall, cut foliage to the ground and mulch well after the ground has frozen.
If you wish, lightly fertilize in early spring with an all-purpose garden fertilizer, such as 10-10-10. They can also be fertilized immediately after bloom. Add mulch to conserve moisture.
When to Divide Siberian Irises
After a few years, if large clumps form, some gardeners divide them to ensure continued bloom. Dig mature iris plants in the spring or early summer after they bloom or in the early fall, well before frost threatens. Loosen the soil carefully and pry the rhizomes loose with a rocking motion. Cut the rhizomes with a sharp knife, leaving each new piece with two fan divisions. Plant the divisions, cover with soil to a depth of 1 to 2 inches (as directed), and keep the new plants evenly moist for 6 to 8 weeks after planting.
The Top 12 Siberian Iris Varieties
- Siberian irises come in a wide range of colors鈥攑urple, blue, pink, lavender, yellow, white, and bi- and tritones. In a poll, the Society for Siberian Irises (SSI) members put these varieties at the top of their list: 鈥楻oaring Jelly鈥
- 鈥極ver in Gloryland鈥
- 鈥楯别飞别濒濒别诲&苍产蝉辫;颁谤辞飞苍鈥
- 鈥楽迟谤补飞产别谤谤测&苍产蝉辫;贵补颈谤鈥
- 鈥楥辞谤辞苍补迟颈辞苍&苍产蝉辫;础苍迟丑别尘鈥
- 鈥楽丑补办别谤鈥檚&苍产蝉辫;笔谤补测别谤鈥
- 鈥楲补诲测&苍产蝉辫;痴补苍别蝉蝉补鈥
- 鈥楽耻濒迟补苍鈥檚&苍产蝉辫;搁耻产测鈥
- 鈥楲补办别&苍产蝉辫;碍别耻办补鈥
- 鈥楳别蝉补&苍产蝉辫;笔别补谤濒鈥
- 鈥楶颈苍办&苍产蝉辫;贬补锄别鈥
- 鈥楽omebody Loves Me鈥
Iris: What鈥檚 in a Name?
In Greek mythology, Iris is the name of the goddess of the rainbow. The iris bloom has been the symbol of monarchs and royal families throughout history. One of the earliest paintings of an iris is a fresco in King Minos鈥檚 palace on the Greek island of Crete. The palace dates from 2100 b.c.
The Bourbon kings of France, including Louis XIV, adapted the iris bloom on royal banners as the 鈥渇leur-de-lis.鈥
The iris is the state flower of Tennessee, and the fleur-de-lis is the emblem of the city of New Orleans, Louisiana.
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Catherine Boeckmann
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I didn't get my siberian iris rhizomes planted until they started to sprout. It is still warm and I am watering them. Will they come up?
Hi, Gayle, We think your irises should come up. Consider, if you had separated a clump some rhizomes (or all!) would have some roots, so stay the course. They might come up later than normal or not have a full growth cycle until next year but they should be ok.
I planted 8 siberian iris (Caesar's brother) in pots indoors. They were doing well and sprouted, I left them outside for a day, forgot to bring them in and green leaves dried up. Will these put out leaves again or have they died? The soil was kept evenly damp. TIA
Love your growth tips
Can I get iris flowers if I plant the seeds from in the spent flowers?
My Siberian irises have just budded and should be opening any day now. Tonight and tomorrow night the temp is going to be in mid 30s to low 30s. Will this harm the buds? Do I need to cover them?
Thank you!
It wouldn’t hurt to provide some extra protection during these unexpectedly cold nights! If you plan to use something like a sheet to cover them, create a sort of tent around the flowers with stakes to hold the sheets off the buds, if possible, in order to prevent the sheet from getting cold and wet and then resting directly on the buds.
Your first photo looks like a bearded iris, not a Siberian iris.
Since iris are such good growers. Can I plant some new ones this spring instead of fall?
The best time to plant irises is in late summer and fall. But if you want to plant some this spring, feel free, however, you won’t have flowers until next spring. And note that bearded irises do not always flower the first year after planting.
