Gardening For Beginners – How to Divide Irises
A couple of years ago, I divided the irises in one of the gardens. It sounds like an easy task. Basically all you do is take a sharp knife and cut the rhizome into smaller pieces. These irises had not been divided for a while so it was a real challenge.
Okay, let's start of with the lesson of the day. Irises need to be divided every 3 or 4 years. Well, make that 3 years. The irises I was working on had been undivided for upwards of 8 years. Also, it was a job that should have been done in July or August. I did it in October. One task, two challenges. What happens if irises are not divided is that they get too crowded and do not grow and blossom like they should. The rhizome gets very big – the largest one I had to deal with was more than three feet long and more than a foot wide. It was woody in the center and actually kind of rotten in places.
The plan was to dig up the rhizome with a spade. I nearly pulled a muscle trying to dig up the huge clump. Ideally you should have the rhizome dug up and hose it down before dividing it but I could not dislodge that massive piece of root. I ended up with a large kitchen knife carving chunks off the ends of the root. I had a bunch of root pieces with a set of leaves attached that filled the wheelbarrow.
Of course I cut up the entire piece in one sitting so then had a huge pile of irises that needed to be attended too as soon as possible. I did not want to hose it down after it was cut so I left out that step. You have to cut the leaves back to about one-third of their height. I have a big old pair of scissors and trimmed each piece back. As I trimmed, I checked the rhizome to see if it looked healthy. Those without leaves, I tossed aside. Also, some of the center pieces had bad looking rhizomes. I tossed them too too.
I spaded up some soil that I had added sheep manure and peat moss to and then dug holes about 5 inches wide. Each hole was just deep enough to cover the rhizome with about an inch of soil. You are invited to mound up the center of the bottom of the hole and put the rhizome on top of this mound and spread the roots around. I did not do this. For one thing, at the time I did not know I was supposed to do that and for another, it was getting late in the day and I just wanted to plant these creatures and have done with it. I planted them about 8 inches apart. I could have planed them a little farther apart but this worked out well for me.
The first summer, they all bloomed but the second summer, they were spectacular. They were nearly 4 feet tall and the blooms were incredibly and lasted a long long time. Oh and a couple of the leafless root parts I tossed along miraculously took hold and great. Unfortunately, they grew under a big bush and did not have the kind of room they needed so I moved them this fall.