Thursday, September 07, 2006

Iris: time to Split!

This Dutch Iris (I think) grows from bulbs, but may naturalize.

It’s an odd time of year to think about Irises, unless you happen to be reading of the mythological Iris, who took messages to the gods along the rainbow to the ends of the earth and lead the souls of women to the Elysian Fields.

The blooming Irises are named for the goddess because of their many colors. Most of them bloom in spring and summer – or not at all.

“Why didn’t my Iris bloom?” is a question I hear a lot, and I even heard a caller ask that of Roland Austin on South Carolina ETV’s “Making It Grow” the other night. Roland’s answer was, predictably, “It probably needs dividing.”

So, when and how does one go about dividing an iris? If it’s a Bearded Iris, this is the best time of year to go about the process. Here is a short version of how.

First, carefully dig and lift the Bearded Iris rhizomes out of the ground. The rhizomes are the long thin tuberous things with whispy roots growing out of them, from which the iris grows. Next, with a hose, clean off all the soil clinging to the rhizome so you can see what you’re doing. Then, cut off the leaves to about six inches. This will remind the rhizome to quit worrying about growing leaves and worry about growing next year’s flowers.

When you can clearly see the rhizome, inspect it for borers and rot. Get rid of any problem areas. Then, using a disinfected knife or pruner, separate the rhizomes into pieces at least three inches long. A fork in the rhizome is a good place to make a cut. Be sure each piece has healthy roots attached to it.

When you’re ready to replant your divisions, and you should replant as soon as possible, dig a shallow hole, about 2 to 3 inches deep and wide enough to spread out the rhizome’s roots. Make a mound in the center of the hole, just above soil level. Soak the soil in the planting hole and place a rhizome division in the center of the mound, spreading the roots around and down the mound. Cover the rhizome with no more than an inch or 2 of soil. “Like ducks on a pond,” is the rule of thumb for planting the bearded iris rhizomes. Plant them too deeply and they won’t bloom.

I found a great website with photos and complete instructions for dividing our bearded iris at

There’s another iris that I once loved, that used to bloom beautifully in my garden every spring. The delicate purple Siberian Irises are my favorites, but they produced nary a blossom this year.

Siberian Irises grow in clumps and mine, sad to say, have taken on a suicide pact with the clumping liriope that grows around them. Though they can be transplanted now, Siberians may do better to wait until spring to be split apart and divested of the grassy interloper. That is a chore I should put high on my list.

I should simply dig up the huge clump, divide it up with a sharp knife, try to pull out all the liriope, and put a piece back in the same spot it came from. Then I can share the rest.