Those blasted borers harm irises [UPDATED]Published 4:00am Monday, April 22, 2013 Updated 6:01am Monday, April 22, 2013
If you have irises, you may well have iris borers. How do you know? The leaves will have brown streaks starting at the top of the leaf.
That leaf will either fall off or be easy to pull off. Another good diagnostic indication is if your irises smell like rotting potatoes. The borer didn’t cause the rot, he just made it possible by boring into the rhizome of the plant.
There is a way to at least reduce the amount of damage. Start this spring by removing all the dead leaves and exposing the rhizomes to the air. If you smell rot, dig up that clump of iris three to four weeks after it blooms. Remove any rotting parts, and cut the leaves to about 6 inches.
Before you replant the rhizomes, sprinkle the hole with an insecticide powder like Garden Guard. In the fall, after the first touch of frost, cut all your irises down to about three inches and bag the leaves. While these treatments will not totally eliminate the borer, it will reduce it.
Continuing these steps for several years should eventually clean up the problem.
Several things Bunkey learned at Garden Day. (You mean you didn’t see him? He had a Hawaiian shirt on with his long chartreuse shorts, flip flops and a big floppy hat as a disguise.)
1. The milk concoction to kill powdery mildew and black spot on roses is one part whole milk, two parts water and a drop of liquid dish soap.
2. To kill slugs — while a strip of copper will slow the stinkers down, it will not kill them. The beer bath is quite effective, but you need a deeper container than a tuna can.
Remember that the lid of the container needs to be above the level of the soil so the slugs can’t get back out after they drop in for a drink. Diatomaceous power is also very effective. The sharp grains shred the snails.
3. Many hydrangeas like sun or at the very least, part shade. There are newer cultivars that are smaller, only about four feet tall for a smaller yard. And, if you like Annabelle, you will love Maxiball.
She is about the same size, six feet tall and wide, but has larger flowers and on sturdier stems.
Cut the old blooms off in the spring and keep pruning to a minimum. Of course Annabelle and her sisters can be reduced by half to keep them in check and blooming.
4. Most mulch doesn’t remove nitrogen from the soil. The exception is bark or sawdust. Sawdust isn’t recommended as it forms a crust and the water runs off it.
5. You only need to mulch a tree to the drip line being careful not to get close to the truck as this can cause rot resulting in the loss of the tree.
Even though the gardens are covered with two feet of snow, you can still do a few things outdoors. Pick off fallen branches; the various treasures your dog has dragged home and, don’t forget, frozen dog dodo. It is much easier to pick up frozen than is the melted stuff.
Bev Johnson is a master gardener for Otter Tail County.