Viewing post #917941 by crowrita1

Pretty much, Mary Ann. Generally, if I "leave them alone," in 2-3 years, I have a clump (again, depending on cultivar...some clump faster, and some, ..not so much). The "center " of the "clump", will start to "thin out", at 3-4 years ( by then, there are usually 2-3 layers of rhizomes in the center....in effect, choking each other out). After that, the cycle continues,....first a thinning of the center, followed by a "thick" center (as the spent rhizomes decompose, it makes room for new rhizome and root systems. When I "steal" rhizomes from a clump (rather than dig, divide, and re set), I usually take from the center of the group...makes for a little harder removal, but, opens up the space for more "blooming size " rhizomes to develop.
Like Paul has said....we all do it in a slightly different way, depending on "our" conditions.....and they ALL seem to work, pretty well . I don't think it really matters...all that much just HOW you "place the rhizomes" , in multiple rhizome plantings (as far as "direction"), unless you want a "show garden" clump, for display purposes.......for most of us, we are either digging and resetting the plants when either , bloom starts to fall off from overcrowding, disease or insects, or grass, make it necessary , or we are sending off iris starts to our iris buddies.....so ,it's some now, some next year, and maybe, if it's been a real, good "season", the whole bed needs done at the same time. A gardened will soon figure out both the growth rates of the plants, and what works best in your conditions.....the iris seem to do pretty well *despite* our "care".