Siberian iris (Iris sibirica) is a gorgeous perennial flower prized for its grassy, lush foliage and stunning blooms in shades of purple, blue, yellow and white. As a clumping herbaceous perennial, it can thrive for years in the garden when its needs are met However, mature clumps will eventually become overcrowded and bloom less vigorously, signaling that it’s time to divide and transplant them Properly timing your Siberian iris transplantation is key to maintaining plant vigor and encouraging reblooming.
Overview of Transplanting Siberian Iris
Transplanting refers to digging up mature Siberian iris plants, dividing the root mass into smaller sections, and replanting the divisions to create new plants. This process rejuvenates crowded clumps prevents disease spread and stimulates fresh growth and future flowering. Clumps should be divided every 3-5 years as blooms diminish. The optimal times for transplanting Siberian iris are
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Spring – Late March to early April after the ground thaws but before new growth emerges.
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Fall – October to early November once foliage dies back but before ground freeze.
Transplanting at the right time reduces stress and allows new plants to establish before extreme weather. Avoid disturbing plants while flowering or going dormant. Proper timing, preparation and aftercare are key for success.
How to Prepare for Transplanting Siberian Iris
Careful planning and preparation should precede digging up and dividing mature clumps. Follow these tips to get ready:
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Select a site with full sun (minimum 6 hours) and well-draining soil. Improve heavy clay areas with compost.
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Prepare new beds by loosening soil, removing weeds/debris, and incorporating organic matter.
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Have containers or nursery bed ready to hold divisions. Disinfect tools.
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Water clumps 1-2 days prior to increase soil moisture and ease removal.
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Time spring divisions as new growth emerges. For fall, wait 6+ weeks after bloom finishes.
Proper planning makes transplanting much easier on the plants and gardener.
How to Transplant and Divide Siberian Iris Clumps
Transplanting involves digging up mature clumps, dividing them into smaller sections, and replanting the healthiest divisions. Follow these steps:
Supplies Needed:
- Spade or sharp shovel
- Sharp knife or pruners
- Disinfectant solution
Steps for Transplanting:
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Loosen soil around clump with spade. Lift entire clump and remove excess soil.
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Using a sharp knife, slice rhizome into sections with 3-5 vigorous fans each. Discard old centers.
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Trim leaves to 2/3rd original size to reduce shock and moisture loss.
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Dip roots in diluted disinfectant to prevent disease spread. Rinse well.
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Replant divisions 18-24 inches apart at original soil depth.
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Water deeply. Firm soil around new plants and mulch beds with 2-4 inches of organic material.
With proper division and aftercare, transplanted Siberian iris will thrive in their new growing sites.
Spring Transplanting Care
Spring is ideal for dividing congested Siberian iris clumps. Follow these spring care tips:
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Time division in early spring once ground thaws but before new leaves emerge. Late March-April is best.
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Check for new white root growth on divisions. Avoid damaging the tender new roots during planting.
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Keep transplants well-watered, providing 1-2″ of water weekly from irrigation or rainfall. New roots are vulnerable.
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Monitor for pests like slugs, snails and thrips that attack new growth. Control organically.
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Apply balanced organic fertilizer 1 month after transplanting to support recovery and growth.
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Remove spent blooms and foliage mid-summer to direct energy to root development.
Attentive spring care reinvigorates transplanted Siberian iris.
Fall Transplanting Care
Fall is also optimal for transplanting with proper overwintering care:
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Delay dividing until 6+ weeks after blooms fade so plants can store energy for recovery. Transplant in October-November.
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Cut foliage back to 6″ after light frost. Mulch transplants 4″ deep to insulate roots from freezing.
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Keep soil moist through fall rains/cool weather. Slowly reduce watering as temperatures decline.
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In very cold regions, install protective winter cover to shield from wind and extreme cold. Remove promptly in spring.
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Apply high phosphorus fertilizer before ground freeze to stimulate robust root regrowth.
Proper fall care will help transplants successfully overwinter and resurge vigorously the following spring.
Long-Term Care of Transplanted Siberian Iris
Getting transplants established is important, but excellent ongoing care is vital for maintaining plant health and encouraging abundant blooms:
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Annually topdress beds with 1-2” of finished compost to replenish nutrients and organic matter. This encourages strong roots and growth.
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Ideally divide and transplant clumps every 3-4 years to prevent overcrowding and rejuvenate blooming. Discard any diseased sections.
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Avoid overfertilization which can cause floppy growth prone to disease. Use balanced organic fertilizer sparingly early in the growing season.
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Provide 1-2” of water weekly during the growing season through irrigation or rainfall. Reduce frequency as plants go dormant.
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Prune spent flower stalks and trim browned foliage in late fall. Leave healthy basal foliage for winter insulation.
With great ongoing care, transplanted Siberian iris will prosper for years as specimens or in perennial borders.
Troubleshooting Transplanting Issues
While generally straightforward, occasional issues can arise when transplanting Siberian iris. Here are some common problems and solutions:
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Wilting transplants – Increase watering, provide afternoon shade, and use anti-transpirant foliar sprays to reduce moisture loss.
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Yellowing leaves – Usually indicates overwatering. Allow soil to partially dry between waterings and improve drainage if needed.
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Slow growth – Apply balanced fertilizer to nourish plants. Ensure 6+ hours of sun and prune encroaching plants.
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No blooms – Can signal too much shade or nitrogen. Move to more sun and reduce nitrogen. Allow 2-3 years for transplants to establish before expecting flowers.
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Pest problems – Prevent with row cover fabric. Or use organic pesticides like neem oil, insecticidal soap, or Bt-kurstaki.
With attentive troubleshooting, potential transplanting problems can be quickly corrected.
Achieve Success Transplanting Siberian Iris
Dividing and transplanting mature Siberian iris clumps is a rewarding way to rejuvenate overgrown plants, control diseases, share divisions, and expand your garden. Carefully follow best transplanting practices for timing, technique, aftercare, and ongoing maintenance. Your efforts will be rewarded with vigorous, floriferous Siberian iris plants for years of beauty. Soon you’ll enjoy refreshed foliage mounds and abundant late spring blooms.
Sun and Moisture for Siberian Irises
Siberian irises are very adaptable and hardy plants. They like lots of moisture in the spring and can survive dry periods in the late summer months but will be healthier plants and develop into specimen clumps faster if kept moist all summer. Try to plant them with other perennials that you normally irrigate during dry periods in July and August. They love full sun (especially in the northern areas) but will grow in light shade.
A mulch of organic matter will benefit the plants in summer by conserving soil moisture and keeping the soil cooler. The mulch is also very beneficial in keeping down most weeds. Siberians are very hardy, but a mulch applied after the ground is frozen helps prevent the heaving and thawing which is responsible for the loss of many perennials over winter.
Siberians are more resistant to disease than most other garden irises. They are, however, not immune to the iris borer. If this is a pest in your area, a systemic insecticide spray is necessary for control. Two applications of Cygon 2E are recommended in the spring. The first, after the first few days of 20 degree Celsius weather, when the fans are three to four inches tall and the second spray when the fans are six to eight inches tall.
Transplanting and Dividing of Siberian Irises
Opinions differ on this subject, and your local climate and gardening practices will influence your preferred time for transplanting, as well as other cultural suggestions made here. A recommended time for digging and dividing older clumps is right after bloom.
At this time new root growth is still active. However keeping transplants moist for the following 6-8 weeks is most important for successful establishment and hot dry weather may decrease survival. So this approach may work best in the cooler, wetter parts of the country. If watering is not always possible at this time, you may prefer early September transplanting when fall rains are somewhat more predictable and the sun’s rays less intense.
Others have found that early spring transplanting as new growth is evident can also be effective. The late spring transplants, if properly cared for will produce more vigorous plants for the next year. Two to four fan divisions are recommended for transplanting and the roots must be kept moist whilst the plants are out of the ground.
Plant the rhizomes one inch deep (slightly deeper in sandy soils) Siberian clumps can grow undisturbed for several years, dividing being necessary when either the clumps become crowded or when vigor declines and blooms get smaller.
Siberian irises normally bloom at the end of the tall bearded season, 24-34 inches tall, with foliage that continues to grow after bloom until 36-40 inches tall.
Some varieties are available that bloom around 10-12 inches tall with neat foliage clumps around 14-16 inches tall by summer. Hybridizers have produced a palette of colours from purples and blues to white, pink lavenders and creamy yellows.
Bitones and special colour patterns of sharp contrast offer great diversity when choosing Siberian irises for special plantings and landscaping. Some varieties have silvery blue foliage, some a fresh green, that is most attractive all summer in perennial borders.
Iris flowers are generally identified by a structure of three upright “standards” and three lower segments known as the “falls”. Siberian irises are of the beardless category.
You may also wish to visit the website of the Society for Siberian Irises (SSI) which is an organized section of the American Iris Society that exists for the culture, enjoyment and improvement of Siberian irises.
Dividing and Transplanting Siberian Iris in a Garden Bed
FAQ
When should Siberian iris be transplanted?
Transplanting: Siberan iris can be transplanted almost anytime from spring until fall if you keep the plant moist and the temperatures are below 90 F and above 32 F for a month afterwards. Dig and divide your plants every 4 to 6 years for plant vigor.
When can I dig up and replant iris?
Although irises can be transplanted at any time, they do best when established in the landscape from August to mid-October, said University of Missouri …Jul 27, 2022
When should I transplant a Siberian iris?
Do not bury rhizomes too deeply or you risk having them rot. For Siberian iris, the right time for transplanting depends on where you garden. In colder regions, transplanting iris occurs in early spring, with late August offering a second option. For gardeners in warm regions, fall provides a good time for transplanting iris.
When should you divide Siberian irises?
While one can divide Siberian irises at any point, late summer to early autumn is best. This practice gives the plant time to gather energy so you won’t miss a blooming period. There are three basic rules for when (and if) to decide when (and if) to divide any rhizomatous flowering plant, such as the Siberian iris.
Is it time to transplant a bearded iris?
It doesn’t matter whether you’re growing bearded iris (Iris germanica) or Siberian iris (Iris sibirica), as plants grow and mature, a day will likely come when clumps become crowded, start to die out or flower numbers dwindle. Those are signals that it’s time to master transplanting iris.
Can irises be transplanted in the summer?
You can transplant irises in the summer after blooming as well. The benefit of transplanting at this time is that you will get to enjoy the blooms prior to transplanting. At this time in the season the leaves will be long and somewhat heavy on the clump.
How do you replant a Siberian iRise?
Replant immediately. When dividing plants in late summer (August), dig up the entire clump, cut back the foliage to 6 to 8 inches and divide the clump into sections with each division containing several fans of leaves and a good root system. Promptly replant the divisions. Siberian irises grow and bloom best in full to part sun.
How often do Siberian irises die?
For Siberian irises, this occurs every 3 to 5 years. Not only will the clump become extra-dense, but you’ll notice the central core of the clump dying out. This core is the oldest part of the plant, and the telltale donut shape of the clump is a clear sign it’s time to divide.