Newsgroups: rec.gardens
Subject: Re: Dividing Siberian Irises
From: jhwilson@miavx1.acs.muohio.edu (Jim Wilson)
Date: 21 Feb 95 17:59:42 -0500

Baker and McKenzie (djdavis@class.class.org) writes:
> 	When is the best time to divide Siberian Irises?  I live in
> Chicago (zone 5 or 6 depending on whose map you believe).  Also, how
> does one divide these most effectively?  Will I have to sacrifice a
> season of flowering if I divide them before they flower this May?

You are right that that could be a significant contributor to their
decreased performance.  These are tough plants, and they can be divided
successfully in early spring or in August-September in our areas.
There are probably more growers who seem to favor the August-September
period.

To divide, cut the foliage down to 8-12" and dig the clump.  Pull it apart
by hand if it allows that, or if it is a tightly connecting type that has
been there a while, you may need to use a couple of pitchforks to pry parts
apart.  Keep the roots wet from the time it leaves the ground until replanted.
When separating the rhizomes, leave two or three fans on each piece--a little
less separated than you would do with the beardless.  Prepare the soil well
for replanting--maybe some peat moss and manure.  Replant with the rhizomes
a couple of inches below the surface and the roots spread.  Use lots of
water as you plant, and make sure the plant remains well watered until it
is fully established; I keep my fall plantings watered until they turn
brown for winter.

Whether you'll have flowers the first year will depend upon the health
of the divisions, your planting skill, your sun and soil, and the variety.
The first year after division is not the best one, but I've usually seen
some bloom.

There are some really nice newer Siberians out now with long bloom
seasons and good form, e.g. Reprise.  The old ones, like Caesar's
Brother and Esther CDM, are still certainly worth growing too.

                                        --Jim