If you've noticed parts of your iris plants turning soft and mushy, usually with a foul smell, bacterial soft rot (BSR) may be taking its toll. It usually appears in the spring as the weather warms. Some causes of BSR include:
- too much water/rain
- poor drainage
- soil too rich
- too much nitrogen or use of manure
- plants are too deep
- winter mulch not removed soon enough.
Problems can also be caused the nitrogen/manure application in the fall. Plants exhibit lush growth, but turn to mush in mid-spring. Go easy on fertilizer.
Too much soil over the tops of the rhizomes traps both heat and moisture. The poorer the drainage, the more important it is to keep the plants near the surface of the soil. Remove mulch from the plants early in the spring. The ability of mulch to retain heat and moisture can have the same effect as planting too deep.
Follow these steps to salvage iris afflicted with BSR:
- lift plants, trim dried leaves and diseased foliage
- cut or scrape rotten or mushy spots
- place iris in solution of one part bleach to 10 parts water and stir for one minute
- place plants in a cool, shady place to dry for a day or two
- dust any wounds with sulfur
- once plants are dry, replant in prepared bed.
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