Irises are one of the near-perfect plants, in my opinion. They are tough, take little water or fertilizer, are deer-resistant, and best of all they bloom in a variety of gorgeous colors.
They ask only that you divide them every three to five years to keep them at their healthy best. As a reminder of their toughness, my daughter in Denver recently received some in the mail from her cousin in Minneapolis. Those had come from my mom's garden in Minnesota about 10 years ago.
Our discussion today applies to bearded iris, of which there are more than 300 species, many of which have been hybridized. Dutch and Siberian irises are different in growth and need different care.
You can identify bearded iris by their three upright "petals," called "standards," and three that curve downward, called "falls." The three that curve downward have a fuzzy strip in the middle, which is why they are called "bearded." Dutch and Siberian irises have smooth falls.
Irises make new growth buds on rhizomes, which are thickened underground stems. Rhizomes have roots on the bottom and plant buds on the top. Once the rhizome has produced a flower, it will not do so again, which is why they need to be divided periodically. New rhizomes will grow in the old bed, but if left untended, your iris bed will eventually become crowded with unproductive rhizomes.
September is the ideal month in the Rogue Valley to divide irises. Scorching hot weather has passed, but the soil is still warm enough to promote growth of new roots. You will need a garden fork or pitchfork, a tarp or old sheet on which to work, a sharp knife, scissors or pruners, a felt-tip marker or plant tags and the garden hose.
Beginning about a foot away from the clump, use the fork to loosen the rhizomes and lift them out. Working on the tarp, shake off any loose soil and gently tease the rhizomes apart. Try not to break the rhizomes if you can help it. Hose off any remaining soil so you can see what you're working with.
Now cut off and discard small or old-looking rhizomes, as well as any that have insect holes or rot. Keep only rhizomes that are fat, are at least 3 inches long, have roots on the bottom, and buds on the top. Cut the leaves to about 6 inches long and write the color or variety name on the remaining leaves. Roots can be trimmed to about 6 inches.
When replanting the rhizomes, remember they like full sun and well-drained soil. Dig a hole 2 or 3 inches deep and wide enough that the roots aren't crowded. Make a little mound for each plant, high enough so the rhizome will come up to soil level. Set the rhizome on top of the little mound, letting the roots hang down. If you are planting several irises in the same bed, allow 12 to 15 inches between plants. Rhizomes must not be buried — they will rot.
Cover only the roots with soil to which you have added a little bonemeal, being careful not to bury the rhizome. Water the new planting well, then sit back and enjoy your new, revitalized iris bed next spring. After blooming, cut back the flower stalk to prevent the formation of energy-sapping seed heads.
Coming up: Cliff Bennett of Chet's Garden Center will teach a class on the fall care of perennials. The class will be held from 7 to 9 p.m. on Wednesday, Sept. 11, at the Southern Oregon Research and Extension Center, 569 Hanley Road in Central Point. The cost is $5. Call 541-776-7371 to register.
Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at firstname.lastname@example.org.