General Information on IrisPlanting Instructions
Plant iris rhizomes mid July through mid September in order for the Iris rhizome to put down roots before the winter. Plant in a well drained sunny location. The rhizome's back should be level with the soil. Water only when planted.Use a low nitrogen fertilizer (first number). Alfalfa pellets are now being recommended as a fertilizer. We use alfalfa at Cedar Ridge with good results and apply it once a year in the spring. Water only when very dry. Best time of day for watering, as it is for all flowers, is early morning. Remove dead or badly spotted leaves from outside fans.
Insect and Disease Control
Best control of disease is to clean up all dead foliage from around the iris in the spring and burn. Borer eggs and fungus spores of leaf spot winter in this material. Do not water iris late in the day as this encourages fungus.
Check fans in spring/early summer for saw toothed leaves which indicate borer. They are, at this stage, between the layers of the fan and can sometimes be killed by squeezing the fan and squashing them. If all else fails use Cygon 2E as instructed. If the iris borers are not killed they will kill the iris.
A more environmentally friendly method to control borer is the use of beneficial nematodes. The type suggested by the supplier is Guardian and should be put on in the spring. Temperatures must be between 15-32 degrees C. when applied as nematodes will not survive below this temperature. They are available through NIC RR#2 Stevensville ON L0S 1S0 (905) 382-2904. Website is www.natural-insect-control.com
Bacterial Soft Rot
Bacterial soft rot is caused by too lush a growth (nitrogen), too rich a soil, too much water, failure to clean dead leaves in the spring or an injury to the rhizome. Agricultural gypsum sprinkled on infected plants is beneficial. Dig and scrape rot from rhizome and air dry for several days. Dust with sulphur of gypsum and replant.
Iris web sites