WCAX.COM Local Vermont News, Weather and Sports-Dividing irises

August 11, 2011

The iris flowers may be all gone and some of the flower patches need a little work. Now is the time to divide your iris. If you have iris that are growing really well, but they didn't flower so well this year, and when you look really close you can see the rhizomes or the roots right at the surface. There's also a dead area in the center with all of the leaves around it. It forms a bulls eye.

It's a sign the irises are overcrowded. You need to dig the clumps up, separate them out, get the healthiest looking rhizomes with at least one fan (set) of leaves, cut back the fan of leaves, and then replant. You can plant them in the same spot or in a new spot. You'll probably get more iris rhizomes than you have room for, so you can give them away. 

When you dig them up watch out for an insect pest on the irises called the iris borer. If you see water soaked streaking down the leaves and then when you dig up the actual iris rhizome you see it's really soft and squishy with holes in it. That's all borer damage.

Don't replant those! Toss them out! How the life cycle works is the adult lays eggs on the leaf in early summer and it travels down through the stem and into the iris rhizome. It tunnels around in the rhizome, opening it up to disease that will kill it, turning the rhizome into a soft, squishy mess. So clean out the rhizomes, get the healthiest ones and replant those. Your iris will bloom again for you next year.  

By Charlie Nardozzi