The many different species vary from low ground covers such as Iris cristata at only 6 inches tall to some of the large Japanese iris at 3 to 4 feet tall. Bearded iris ranges from about 6 inches in the miniatures to more than 3 feet in the large types. Their growth rate varies by species and type. The bold sword shaped foliage is also an excellent contrast to the more mounded forms of many garden plants. Bacterial soft rot is the most serious iris disease.
Soft rot causes the rhizomes to become mushy and have a disagreeable odor.
Remove any yellowing leaves promptly to help prevent spread of the disease. Iris leaf spot, caused by a fungus, is the most common disease. Remove all leaf and other debris in fall, since diseases and insects often overwinter on old foliage. Iris borer is the most serious insect pest of iris. Bacterial soft rot readily attacks borer-infested plants.