Bearded Iris Culture


Planting Your Rhizomes

Prepare The Bed:

Prepare a neutral to slightly alkaline soil bed at least 10" deep; mixing in a 5-10-10 fertilizer at this time is recommended. Ideally, the soil needs to be firmly packed down yet crumbly for ease of cultivation. Rhizomes planted in soil that is too loose tend to settle below the soil line which may lead to diminished performance. Soil that is too heavy may lead to stunted growth and health issues. However, irises are pretty darn tough and often thrive under conditions that are contrary to these recommendations. The iris will let you know if it doesn't like where it's growing!


Depth To Plant:

In the Pacific Northwest, planting the rhizome so that it is partially exposed (like a duck on water) is recommended. For rhizomes that have long roots, it is easiest to dig your planting hole, build a mound of soil (peak level with planting bed soil level) in the center of the hole, place your rhizome on top of the mound, spread the roots over the mound and then fill soil around the roots, packing it firmly as you go. Newly-set plants should be kept moist until the roots are growing well. Note: freezing weather may cause "heaving" of the soil. Simply press the rhizome back in to soil level.


Distance Apart:

In regards to individual plants, the closer the plants are, the sooner dividing will be required (3-4 years) and heavier fertilizer will be needed. Greater distance between plants will mean more time before dividing is needed (4-6 years) but the bloom impact will not be as significant for at least 2-3 years. If you are planting for mass impact (3 or more rhizomes; triangular planting pattern), the same considerations will apply, but chances are division will be needed sooner. For close or mass planting, we recommend 8" apart for MDBs, 12" apart for SDBs, 18" apart for IBs, BBs and MTBs, and 24" for TBs. The best planting time is July through August in the Pacific Northwest area; sooner is better to allow the plant to become re-established for next year. When dividing, dig the plant, remove and discard the old center rhizomes and replant the new fans. You may cut out the old centers with a knife while they are in the ground if you do not wish to lift the plant. If you choose to follow this procedure be sure to sterilize the wounds with a 5% bleach solution or a Clorox wipe and allow to dry before soil covers the remaining rhizomes.


First Year Care:

Until the plant is well established, extra care may be necessary. If a bloom stalk is produced the first year, you may want to consider removing it so the energy will be directed to growing strong roots and increases for the following year. If the plant is healthy and well established, and you decide to jeep the bloom stalk, staking the stalk is highly recommended to help prevent the weight of the bloom from uprooting the rhizome if it falls over. Please keep in mind that allowing bloom the first year may lead to bloom-out, where the rhizome and plant are so taxed that they die or fail to perform well for several years.


When To Plant / Dividing Bearded Irises:

The most common questions about bearded irises is when to divide and how to divide. In the Pacific Northwest, dividing of bearded irises can be done any time of year as long as the ground can be easily worked. However, the best time to divide is from mid-July to the end of August. This time-frame provides the best conditions for the plant to re-establish itself before the cold weather sets in; the earlier the dividing and replanting is completed, the better! When dividing, dig the plant, remove and discard the old center rhizomes and replant the new fans. If the clump is getting crowded, but you don't what to dig and divide yet, you may cut out the old centers with a knife while they are in the ground. If you choose to follow this procedure be sure to sterilize the wounds with a 5% bleach solution or a Clorox wipe and allow to dry before soil covers the remaining rhizomes.

  1. Dig the clump. Trimming the foliage by half before digging will ease handling.
  2. Knock off as much loose soil as possible. Wash off remaining soil with water.
  3. Break off healthy rhizomes from old rhizome, or cut off with a sharp, sterile knife. Save only the healthiest for replanting!! Donate or compost the rest!!
  4. Neatly trim foliage to about 6". A pointed top is traditional.
  5. Replant in triangular pattern, cut rhizome ends to the inside for a good-sized clump.

Maintenance:




Top of page