THE VIRGINIAN-PILOT
Copyright (c) 1997, Landmark Communications, Inc.
DATE: Sunday, February 9, 1997 TAG: 9702070131
SECTION: HOME & GARDEN PAGE: G2 EDITION: FINAL
TYPE: Column
SOURCE: Robert Stiffler
LENGTH: 73 lines
IRIS ARE USUALLY an easy-to-grow perennial for this area. They normally bloom prolifically, and the only serious problem that may plague them is rot.
Evelyn Thomson-Lakey of Virginia Beach wrote to me in the fall describing problems with her iris. She says: ``Last year my 5- to 8-year-old, well-cared for and periodically divided irises began dying. This year they are all but gone.
``I find leaves fanned out on the ground. The rhizomes are soft, rotting and smell bad. I have been told there is no cure. This attack seemed to come after I divided a dense growth.
``Can I ever replant irises in this raised, well-drained bed? Is the bacteria permanently in the soil, ready and waiting to destroy any new plantings? Is there a dust or spray I should have used after dividing and replanting?
``If I can't plant irises, what can I plant that would not be susceptible to this attack? What is happening to these beautiful plants?''
I grow iris but am not an authority, so I asked Bill and JaNiece Mull, longtime authorities in the Tidewater Iris Society. Here is their reply:
``Many people lost 90 percent or more of their iris in 1996. It has been a very bad year for iris.
``Because we're farmers from Iowa, we believe in rotating iris at least every three to five years. It appears that iris that have been in the same soil for several years tend to have more problems with bacterial soft rot, which is what it would appear E. Thomson-Lakey has. Hot, wet weather tends to cause this type of rot.
``Never, never mulch bearded iris. Iris rhizomes must be exposed and out of the soil so they will get direct sunlight. Mulching can cause them to rot.
``There are two, perhaps three, types of rot that attack iris. Bacterial soft rot appears to be the most common and the easiest to spot, mainly because of its bad odor.
``When you destroy the rot in the rhizome, you must also destroy the soil around the rot. Best way to handle this is to take a large garbage bag and put the diseased iris and soil in it. We use rubber gloves, which we also destroy. Make certain that everything you use (knives, spades, etc.) are sterilized after use or thrown away.
``Rot is very easy to transfer from bed to bed. Once the rot gets in a bed, it often will take out all the iris in that bed and can be easily transferred to other beds.
``You can sterilize the soil, which will destroy the bacteria in the soil. The common household method of handling this is to cut out the rot with a sterilized knife, dipped in a solution of Clorox brand bleach and water, and hang the rhizome in the sun. The sun tends to take the Clorox out of the rhizome.
``Another method is to cut or dig the rot out of the rhizome while it is in the soil and generously sprinkle Comet brand household cleaner, which contains bleach, around the rhizome. Some people take a 5 percent or 10 percent solution of bleach and water and pour that in the soil around the rhizome, after the rot has been removed.
``There are commercial products available, but we are not certain they are any better than Clorox.
``Irises seem to put in or take out something from the soil, which tends to have a negative effect on the soil over time. Iris growers may disagree, but more and more evidence supports the need to rotate iris. If you can use virgin soil, you will raise the best iris, but you can still get rot during hot, wet weather.
``We're told that commercial growers rotate their iris, growing iris one year, then for two years they put in different crops. The fourth year, they go back to iris. You can grow almost any flowers, daylilies, annuals, perennials, vegetables or grass in the area where you had been growing iris.
``Rot doesn't normally affect beardless iris, such as Siberian iris. If you want to avoid rot, you may want to grow the beardless type.''
Thanks to the Mulls for taking time to help solve the problems of iris and rot. They sell daylilies and iris from their home garden. Call them at 858-5521 or fax 858-5529.