When do I cut yellow iris foliage back?
Certified GKH Gardening Expert
You will only want to cut it back once it is fully dead. This will be shriveled and brown by the time you will do so.
Sometimes, this can be normal. If this is happening while there is little foliage on the plant, then there could be an issue.
Fungal issues can be common where there is lots of rain, or when they get overwatered for an extended period of time.
A fungicide may be necessary. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
This article will help you to care for Iris plants: https://www.gardeningknowhow.com/ornamental/bulbs/iris/iris-plant-care.htm