From: jwilson@bach.udel.edu (Jim Wilson)
Subject: Re: Siberian Iris question (was Those Wonderful Iris!)
Date: Tue, 8 Jun 1993 02:37:53 GMT

bbeer@stein2.u.washington.edu (Bob Beer) writes:

> Fertilization: Spring and Fall, and avoid high-nitrogen
> fertilizers.  Lots of iris dealers sell special Spring and Fall
> formulas.  Iris, especially the tall bearded ones, are "heavy
> feeders."  Before you plant them, it is a good idea to mix some
> fertilizer right into the soil.  Manure is good (composted, not
> fresh) too.  I don't believe they are extremely picky about pH, but
> avoid really acid soil.

I'd like to expand upon a couple of Bob's comments, mainly in the idea
of differentiating between types of irises, because that really does
make a difference in some of these areas.  The real heavy feeders in
the iris family are the Louisianas, and to a lesser extent the
Japanese; the others like a little balanced food, but they willfood
but do great with not much.  Most iris do appreciate some composted
manure in the soil, but be careful not to overdo it in some climates
with beardeds or you will be encouraging rot.  Bearded iris don't like
really acid soil, but Siberians and Japanese and Louisianas love it
and won't do well in neutral soil--a pH of 5.8 is a good target that
will keep many of these beardless types happy.  All of these like lots
of sun, and very few irises don't, but there are some like I. cristata
and I. tectorum that do prefer partial shade.

			Splitting hairs and dividing irises, --Jim
-- 

Jim Wilson, Instructional Technology Center, University of Delaware
Newark, Delaware 19716                      jwilson@brahms.udel.edu