neighborhood garden for August 20, 2016


time to plant your and/or divide IRIS

by Gladys jeurink


          We need to be planting our new iris, and/or dividing iris that have been in the ground for three years or longer, before too late in the fall. The best time to do this is in August or early September. The iris have been storing up energy and producing new plants since finishing blooming. Remember, iris are not water loving plants.  As they get started in the spring, watering is needed, but later they prefer a full sun, well drained spot. Too much water gives high leaf growth and too little bloom.  But also remember, they are not a desert plant. Too hot a sun all day fades their blooms.

          Much of Lincolnís soil suits iris as they like a soil neutral or slightly acid.  A goodly amount of compost in the soil is desired, but too much compost will retain a lot of moisture longer and encourage root rot.  If you use manure, dig it in deeply after decomposing so that it will be below the rhizomes.  They are not heavy feeders, as too much nitrogen promotes foliage instead of flowers. 

          Now that their new soil is ready, dig or buy your new plants. When digging and dividing existing iris, I like to cut the fans (leaves) back to about 6-8 inches (so that the roots donít have too much to support) and divide the roots. I like to make a hole about 4 inches deep and 6 inches wide.  I hold the rhizomes at the top of the hole so that it will be barely covered with soil when Iím finished.  Sometimes, I even leave them showing a little. Then, I take the roots and spread them out and down and fill in the soil over them. They will need to be watered several times to settle the dirt closely around the roots. Growth is from the front and sides so you can plant them to grow in the direction you would like. 

          How far apart?  That depends on how soon you want to transplant them.  I like at least 2 feet between clumps and even then by 3 years they are crowded.  The tighter the crowding the poorer the bloom crop will be. Also, if you wait and plant too late in the fall so the roots donít get established, freezing and thawing will heave the plants out of the ground. 

          Before you plant your new iris or the ones you just divided, check for disease and insects.  Here in Lincoln we are favored by borers.  Look for their tunnels and also the borers as they are helpers of root rot.  For disease control and to drown any borers and insects, I make a solution of one part chlorine (bleach) to nine parts water in an old wash tub and soak the rhizomes not more than an hour or two. The insects and borers will float to the top. Any plastic bucket or other container will work fine. Soaking for even a half hour will kill the insects, borers, and disease. The easiest is to clean the dirt from any plants dug up; throw out any plants that are mushy from disease, rot, or borers; divide the rhizomes as needed; and then put them into the solution until you are finished. Let the rhizomes dry in the sun before planting.

          Borers lay their eggs in the fall on the old foliage, giving us a very good reason to clean up all old foliage in late fall or very early spring.  Bob Gilmour, a Master Gardener, used to put Bordeaux powder on his plants after cleaning up the bed in the fall, and then again in the spring as growth begins.  Bordeaux is an organic copper fungicide.

          As iris grow, the mother plant will die out and leave a dead spot in the middle with daughters all around.  In time the whole bed will be crowded with the daughters, and the blooms will be smaller as it is those daughter plants that produce the new flowers.  Check your iris bed now and see if it needs to be divided.  Remember, the best time to plant new iris or dig up and divide old iris is August and early September so now is the time to get started.

Copyright 2016