Divide Irises for Better, More Abundant Blooms

By Doug Coffey, Fairfax Master Gardener
Bearded irises (Iris germanica) can provide your garden with an amazing palette of color from early spring through late spring. Some will even rebloom in the fall. But what do you do when that profusion of color starts thinning out?

overgrown iris

Overgrown iris bed

If your irises haven’t been putting up blooms the way they once did, it may mean they are overcrowded and require division. The good news is that August is the perfect time to tackle that task.

If your clump of irises is in a sunny location, receiving at least six hours of sun, you may only need to cut out the dead rhizomes in the center of clump. New bloom stalks will not grow from dead rhizomes. Removing the dead material in the center will allow new division growth to expand back into that area.

It is time to divide when:

  • Your irises are growing in an area that has become too shady.
  • The clump is overcrowded and bigger than you had intended it to be.

A clean iris bed is a healthy iris bed

The tools you will require for this project are a spading fork, a sharp knife, a pair of garden scissors and a water hose with a nozzle.

Begin with the spading fork. Work your way around the iris clump to loosen the soil and dig up the entire clump. Shake off any loose dirt, and then spray the clump with water from your hose to remove all the soil. Carefully pull apart the entangled root and rhizomes into separate individual plants, and wash these clean.

overgrown clump

Cut out and throw away overgrown clump

Now it’s time to get out your knife. Use the knife to cut away all of the soft and dead tissue from the rhizome. Because irises will only put up bloom stalks