What Is The Best Time To Divide Bearded Iris?

The Iris (EYE-ris) genus is somewhat complex for its size of about 300 species. This genus has five subgenres, some of which have their own sections.

The subgenus Iris is perhaps the most popular, containing the famous bearded irises.

Blooming Bearded IrisesPin

Bearded irises (also known as Pogon irises) are one of six sections in the Iris subgenre and can be much pickier than their relatives.

Dividing a bearded iris when dividing other irises may result in the iris failing to bloom the following year.

When To Divide Bearded Iris

Summer is the best time for dividing if you want blooms the following year.

But, there are some other points to consider when dividing a bearded iris.

Picking The Best Time To Divide

There are a few signs that it’s time to divide your bearded iris.

As a general rule, rhizomatous irises (subgenera Iris and Limniris) will need to be divided every 3 to 5 years.

The clump will begin to bloom less due to overcrowding.

And it’s not unusual for the oldest part (often in the middle of the Bearded Iris cluster) to die out.

Bearded irises bloom in the spring, making the best time for dividing during the summer months, most often in July or August.

This not only allows you to enjoy these beautiful flowers, but it also gives the divided plant time to establish itself before winter.

Uprooting The Iris

Here are the steps to follow:

  • Dig around the entire clump and gently lift it using a garden fork or spade from the ground.
  • You’ll likely need a second pair of hands, as the clumps can become quite heavy.
  • Gently knock away any excess dirt to expose the rhizomes.

Selecting Division Points

This is an ideal time to check for damaged or diseased rhizomes and select the healthiest portions for division.

This is an ideal time to check for damaged or diseased rhizomes and select the healthiest portions for division.

Closely check for any signs that suggest the presence of iris borers, including:

  • Softness
  • Discoloration
  • Foul smell
  • Holes

These are all signs that you should discard the rhizome.

You’ll want to check for firm, light-colored rhizome sections that are at least 1″ inch wide and 3″ inches long.

The rhizome should also have a fan of at least 4 leaves and healthy roots growing from it.

A rhizome that has suffered some rot damage may be salvageable if you can remove the rot down to healthy white tissue.

But this is rarely necessary unless there are no healthy rhizomes left.

Division

Division is a straightforward process done by the following steps:

  • Snap the rhizomes where they join or use a sharp, sterile knife to cut them apart.
  • Choose to separate each healthy rhizome or divide groups.
  • Discard the old central rhizome when you do so.

The rhizomes can survive a few days before replanting if you want to let the wounds heal over.

Or, you may plant them immediately.

They don’t have a long shelf life, so it’s best to plant within 48 to 72 hours.

One popular method of immunizing the rhizomes is to soak them in a solution of 1 part bleach to 10 parts water for 30 minutes. Then let them dry.

This method can kill any pests or fungi on the rhizome that you missed and give the rhizome a little extra protection once it’s planted.

Planting The Rhizomes

Before planting, check the intended spot to ensure it has at least 6 to 8 hours of full sun per day.

Also, do a soil check to see if you need to amend it.

Here are the following tips for planting:

  • Because bearded iris plants hate to be moved, space them out 12″ to 18″ inches apart.
  • Form groups of 3 to 7 rhizomes when you’re dividing more than once cultivar or species.
  • Dig out a small hole no more than 4″ inches deep.
  • For bearded irises, it’s best to make a little mound in the center on which to perch the rhizome.
  • Then, spread its roots out evenly down the sides of the mound.
  • Make sure all fans are pointing in the same direction when planting a group.
  • Gently backfill the hole to avoid shifting the roots, then firm down the soil.
  • Expose the top of the rhizome as iris rhizomes react to the weather. Planting them too deep can prevent blooms from forming.
  • Water thoroughly, and be sure to keep the soil moist (but not wet) until you see new leaves beginning to grow.

Note that you may get only a few blooms the first spring after planting, but the years after will more than make up for it.

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