Dear Tamsin:
I know Eb will give you the real response, but I had to put in my two cents. There is an old gardening saying in this country that Bearded Irises must be divided only after Memorial Day (the end of May) and before Labor Day (the beginning of September). It certainly would have been simpler to say, "Divide them in summer," but that is a relative term depending on what part of the country you live in. The problem is, so are those deadlines. Down here in the south, nobody in his right mind would divide Irises in early summer, because they won’t have bloomed yet and they will be too stressed by the heat to re-establish. On the other hand, maybe up in Maine, where the growing season is so short, if you don’t get them divided by the end of June, you’re out of luck. The rule worked perfectly when I lived on Long Island . . . but no matter, I would never have fainted at the sight of a neighbor dividing them two weeks after Labor Day unless we were having a freakishly cold spell! So I think your neighbor may be a little out of line, though I hate to say it of a fellow Master Gardener. He probably just thinks you, as a real live hort, should know better!
Here in South Carolina, I often wait until the end of September to divide my Irises. It’s just too hot too long to do it any sooner. Plus, that way my rebloomers often get a chance for their second bloom! Yes, I always have an ulterior motive!
Let me know if you want some Immortality, the classic white rebloomer. I divided them 2 or 3 years ago and they have spread like a rumor. In a couple weeks, or when you find a new place for your Iris bed, come over and we’ll dig you some up. I am really proud of them. This year I’m putting it a bunch of Let’s Boogie off by themselves, where their riotous colors won’t bother any neighbor plants. I usually stick with rebloomers, but I’m just crazy about those colors on Let’s Boogie!
By the way, what do you do with all that diseased foliage from your "scrap heap" border? I can’t burn it (within city limits), I refuse to risk the compost pile with it, and I don’t have a place to bury it.
Have a lovely day!
Kay
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