I've read many online articles about cutting back foliage on Bearded Iris. Already cut them back to 8" and cut out any that were fully yellow/brown but made sure to leave green fans to soak up sunlight to get ready for next year's bloom.

Since we had relatively warm weather up until this week all remaining foliage is still GREEN on both plants left in place/not divided and divided/transplanted babies.

Should I mulch after good, hard frost later in Dec. and leave green foliage on until late winter/very early spring and then remove? Don't like risk of leaving too much foliage around in case there's a problem with "pests" that I'm not seeing even though all bulbs looked amazingly "clean" when dug up and washed off.

Hesitate to leave foliage on until spring as I assume I'll not know difference between what Iris needs and what's superfluous from prior year's greenery.

These are 30 year old irises belonging to my father and I don't want to do the wrong thing!

Note that these irises were NEVER divided before this year, got no mulch except what blew onto beds, etc. and had some bloom but not what I expect they could have with proper division and seasonal care.

Any input from experienced Bearded Iris growers would be greatly appreciated.

Chance I might have left well enough alone for my father but I'm pretty sure that many rhizomes can have more blooms than he's gotten in recent years. There were plenty of healthy babies with their own little fans!