Saving Overgrown Iris

July 18, 2013 by Schreiner's Iris Gardens 147 Comments

Nature happens….

Let’s say a friend told you about this patch of once-lovely Iris which has become completely engulfed by grass… (or maybe that friend is you…) You tell your “friend” that her situation reminds you of something you once read by Sara Stein*: “I appreciate the misunderstanding I have had with Nature over my perennial border. I think it is a flower garden; she thinks it is a meadow lacking grass, and tries to correct the error.”

July, August and, in some areas, September, is the time to assess the situation in your Bearded Iris garden, and rectify the misunderstanding you might have with Nature. If it’s been a few years (say three to five) since you planted your Iris, it is likely that the clusters have grown, and over-grown, themselves into a large mass of rhizomes 12 to 24 inches wide. If you are (or know of) that friend described above, fear not. If you see foliage above the blanket of grass, the Iris can be saved! Read on.

Before you reach for the shovel, though, let’s review some tips on dividing and transplanting the new Iris babies.

Iris Identity: If you have your Iris labeled, you will want to label all of its babies. Prepare tags of some sort to help you keep track of what you are transplanting and where. If you haven’t labeled the Iris in your garden, then proceed unfettered by the bondage of labels….

Digging the clumps: Depending on how densely packed the Iris clump is, you may wish to dig up the entire mass and work on it out of the ground. In the case of the clumps overgrown with grass, you’re best bet is to dig up the whole shebang. Carefully pull the soil and grass away from the rhizomes and roots so that you can see what you’re dealing with. Take care to remove as many of the grass roots as possible. Once cleaned up, you will likely find that the mass of Iris resembles a tangle of fresh ginger, or small oblong potatoes, some of which will have fresh green foliage attached.

New growth on left and right of spent rhizome

Separating the plants: The rhizomes with the foliage are the plants you will keep. Any rhizome which has no foliage is “spent”, and will not bloom again. It can be discarded. At this point, you can decide how many of these new plants you’d like to replant. Some of the new growth may yet be quite small, the size of a cherry. These are called “nubs”, and will have tiny green leaves. You can plant these, but expect possibly two years at least before you see any blooms.

To separate, carefully snap or slice the rhizomes at the junction between the old plant and the new growth. Take care to disentangle the roots so that the new plants retain their set of roots.

Cut or break off new growth from original rhizome

If the foliage on the new plant is very tall, you can trim it back to 6 inches to make transplanting easier.

Prepare soil for transplants: For the area where you intend to plant the new growth, dig up the soil 6 to 12 inches deep, remove weed sprouts, mix in some organic mulch or a low-nitrogen fertilizer (follow manufacturer’s recommendations for quantity and ratio) to give the soil a nutritional boost. Break up large clumps of soil and smooth out the area. Plant your new iris so that the roots are covered but the top of the rhizome is showing above the surface of the soil.

Water in: Water at the time of transplanting. Newly set plants need moisture to help their root systems become established. Specific watering requirements depend on your climate and soil, but keep in mind that deep watering at long intervals is better than more frequent, shallow watering. Once established, Iris normally don’t need to be watered except in arid areas. It is always better to underwater than over water. Too much water can induce rot.

What to do if you have more Iris shoots than you know what to do with: Consider donating the extra plants (labeled or unlabeled) to a nursing home, school, or community center in your area. You can also check with your neighbors to see if they’d like any of the offspring.

Getting ready to divide your Iris? Tell us what you do with the extras. We’d love to read your comments.

*Sara Stein, influential advocate for gardening with native plants, and author of “Noah’s Garden: Restoring the Ecology of Our Own Backyards” (Houghton Mifflin, 1993).