Dividing Bearded Iris
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!
Keep in mind that if the clump is simply getting crowded but you don't what to dig and divide yet, the old rhimomes within the clump can be cut out with a sharp a knife while they are in the ground, leaving the younger rhizomes and fans undisturbed. If you choose to follow this procedure be sure to sterilize the wounds with a Clorox wipe and allow the wound to dry before soil covers the remaining rhizomes.
Step 1
The first step is to identify the clump to be dug. This may seem like an obvious step, however many factors can be involved when determining whether or not a clump needs to be divided.
- Are the rhizomes growing over each other?
- Is there an empty area in the middle of the clump where there are no fans, only old rhizomes?
- Is there strong bloom or has the bloom quantity/quality deteriorated the past few years?
Step 2
Dig the clump out of the ground. Depending on the size of the clump, this can be a challenge or relatively easy.
- Moderatly moist soil is easier to dig.
- Using a digging fork may be easier for heavier soils.
- In some cases, a quick initial trim of foliage will make to clump easier to handle.
Step 3
Remove the soil.
- Gently tap the root ball with a shovel or digging fork to remove most of the soil.
- A moderatly high powered fan water spray can be used to finish the job; muddy but effective.
Step 4
Gently pull apart the clump.
- Some rhizomes can simply be broken apart.
- Sometimes a sharp knife cleansed with a clorox wipe will be needed to cut rhizomes apart.
- Discard the old fan-less rhizomes!
Step 5
- Some rhizomes can simply be broken apart. There is a train of thought that breaking the rhizomes apart allows for natural healing of the exposed rhizome.
- Sometimes a sharp knife cleansed with a clorox wipe will be needed to cut rhizomes apart.
- Discard the old fan-less rhizomes!
Step 6
What are the plans for rhizomes?
- For a full clump in fewer years consider keeping a year old rhizome with two or more strong, healthy fans attached.
- If lining-out rhizomes or sharing/donating, individual rhizomes are best.
Step 7
Make your divisions.
- Single fans with evidence of increases will form a mature clump quicker.
- Trim the foliage to about 9 inches from the rhizome; angled cuts to form a point are typical but not necessary.
- Be tough! Do not keep wimpy rhizomes to replant. They will take longer to mature and may require more TLC to perform well.
Step 8
Treat the divisions before replanting or donating.
- Soaking for a few minutes in a mixture of Ivory soap and water will help prevent the spread of disease and help discourage insects from taking up residence.
- For deeper cleaning, especially if sharing or donating, soak the rhizomes and fans in a standard solution of Neem Oil and water.
Step 9
Planting divisions can involve many factors:
- How fast do you want a full display? Three divisions planted in a single mound will have a larger showy display sooner.
- How soon do you want to have to divide again? A single rhizome clump will not need to be divided for 4 or 5 years.
- For more in depth instructions, visit our Bearded Iris Culture page!
