August, to the farmers throughout the South of Mid-America, means that crops are "laid by," and the time for taking it easy has arrived. This is true to a large extent of the gardener, also. Much of the hottest part of the summer has passed, and only a few more days of extreme temperatures will remain to sear the garden flowers.
Actually, plants undergo a physiological change and begin a resurge of growth for fall bloom. Many annuals or seasonal color plants have made their contributions and passed on. Others will be making their last efforts to reproduce themselves. Nature forms the flower on a plant for the sole purpose of attempting to reproduce its kind.
Some of the attempts never succeed, but the flower that is produced does reward the gardener who provides the cultural requirements for the plant. This attempt at reproduction is the reason why lawn grasses are all throwing out unsightly seed heads, and why late planted annuals will bloom on short or under-sized plants. This natural phenomenon makes it possible to have a splash of color in gardens until frost curtails all visible activity in the garden.
Iris in August is a very important month for the bearded iris throughout most of the South. Most new plantings begun in July can be continued during August. August is also a good time to divide and reset the old clumps. Many gardeners divide and reset approximately two weeks after flowering has ceased. Others wait until August and do all of this work at one time.
The foliage should be cut on a slant into fans four to six inches above the rhizome, and all faded or dried leaves should be completely removed. Dig the rhizomes out and remove all the soil either by shaking or washing. Cut away the old corky rhizomes with a sharp knife and dust the exposed area with lime, which will cause this cut to sear over as a precaution against soft rot. By horticultural standards one healthy "fan" is necessary for each rhizome, but actually two or three "fans" will insure more bloom the first season.
With more moisture present throughout the South, soft rot will appear in many plantings of irises. This fungus disease is most destructive and difficult to control. It is sure to be present where irises have been planted too deep, or where there is poor circulation of air. A precautionary measure is to soak the rhizomes in a fungicide 30 minutes before planting.
When this fungus disease is discovered in the iris, the rhizomes must be dug immediately. You can either prune roots or cut all of the diseased portion cut away. The remaining parts should be thoroughly dried, dusted with lime or other drying agent, and treated with a fungicide. If possible, these should be replanted in another area of the garden. The soil where the diseased plants were growing should be discarded to prevent further spread of the disease. The matured fungus bodies are very tough, and resist many treatments that will kill other types of fungi.
As a general rule, irises are not susceptible to a great number of pests, but many are influenced by weather conditions and excessive moisture can cause infestations of all kinds. The wise gardener will be on the lookout for these following periods of excessively wet weather.