September 5, 2003 at 10:19 a.m.
If you are preparing a new bed, remember that location is important. In addition to the cold treatment during the winter months, they also need warmth and bright light to trigger proper growth in the spring. The soil near foundations will warm up faster, particularly on southern and western exposures, resulting in earlier flowering. These areas should be well mulched to keep soil temperatures at a constant level and sheltered from winds. The soil should also have good drainage.
New beds need to be free of debris, such as rocks and roots. Work in organic material such as peat moss, fine compost or shredded leaf mulch. This should be worked in to a depth of 10 to 12 inches. It may be beneficial to work in some 5-10-10 fertilizer according to the directions on the bag. This must be mixed into the soil very well before planting the bulbs.
Iris rhizomes sit just below the surface. To dig up a clump, slide your garden fork carefully beneath the clump and lift it out of the soil. Spread the clumps out on the lawn and wash them off with a garden hose. Once you can see the rhizomes, it's not difficult to cut each clump into smaller parts for replanting. Each clump of iris will have two or more fans of leaves growing out of its rhizome. Use a sharp knife to divide the rhizome attached to it. Discard the oldest woody part of the original rhizome, along with any parts that are soft or rotted.
Next, trim away broken roots and cut the green foliage back to four to six inches. You can replant the rhizomes immediately or store them for several weeks in a cool, well-ventilated place.
Plant groups of the same iris in drifts with their leaf fans facing outward from the center of the garden. Leave a minimum of eight inches between each rhizome for expansion. Rhizomes should be positioned horizontally, right below the surface.
Dig a shallow hole for each rhizome, with a small ridge of soil for it to sit on. Spread the roots to both sides of the ridge. Put more soil over the rhizome and roots and water it thoroughly.
When the soil begins to freeze in November, mulch the iris with four to six inches of straw or marsh hay, or ten to twelve inches of dried leaves.
The iris borer is a serious problem for iris growers. The borer hatches from eggs laid on leaves in early spring. A sign of iris borer activity could be the premature yellow and brown foliage on the entire plant. When you lift up the iris rhizomes, trim away rotted portions or discard the entire plant. The iris borer causes a bacterial soft rot that eventually kills the entire plant. A spring spraying of Orthene or Cygon when the leaves are five to six inches tall has been the usual defense.
Parts of this article were taken from earlier writings by Bee Tolzmann, Master Gardener and Deb Brown, U of M horticulturist.
To learn more about this topic or others, go to the U of M Extension Service web page at www.extension.umn.edu and search. Or, you may call our Yard and Garden Line anytime and leave a message at (612) 624-4771. A Master Gardener will return your call. The Master Gardeners also staff the Extension Office on Monday from 4:30 to 8 p.m. Call (651) 674-4417 or drop by with your samples and gardening questions.
Applications for the 2004 Master Gardener Training program are now available from your county extension office. The deadline for Chisago County is September 19, 2003.
You can be a Master Gardener
The Master Gardener program was created in 1977 and is administered by the University of Minnesota Extension Service. Most counties in Minnesota have a Master Gardener Program.
To be a Master Gardener you need to have an interest in gardening and a desire to share this with others. You must be enthusiastic, willing to learn, and able to communicate with diverse groups of people. You must attend the Master Gardener Core Course, which consists of 48 hours of classroom instruction by University specialists, and complete an internship of 50 volunteer hours the first year. To continue as a Master Gardener, you must perform 25 hours of volunteer service each year through your local Extension office.
Volunteer activities include answering phone requests for gardening information, working with community groups, holding plant clinics, giving presentations, setting up horticultural displays, writing articles for local newspapers, and teaching community education classes. Master Gardeners may also function as resource individuals for horticultural questions in their local Extension offices.
To apply for the program, contact your local county Extension office by calling (651) 674-4417. The application deadline is September 19. The 2004 Core Course will be held in St. Paul from January 13 to February 7, T, TH evenings from 6 - 9 p.m. and Saturday, from 9 a.m.-4 p.m. Information can also be found on the Master Gardener website: www.hort.agri.umn.edu/MG/mast gard.htm
The University's Yard and Garden Clinic has experts to answer questions on horticulture, plant disease, and insect problems between 9 a.m. and 1 p.m. weekdays. Call (612) 624-4771 in the metro area or (888) 624-4771 from outside the metro area. There is a $5 fee, which can be billed to a major credit card.
The clinic is one of the services available through Yard and Garden Line. Also available are free recorded messages 24 hours a day from Info-U. And at no charge, callers can request a return call from a Master Gardener volunteer in their county or can speak to a wildlife or water quality expert.