Re: monoculture

Mary Forte wrote: 

<< Well, I've really noticed this year that my irises planted out in my mixed
beds have little to no leaf spot.  My irises that are planted in iris-only
beds have much more leaf spot...  So I'm wondering if my irises in the mixed
beds are spot-free because they are  farther apart from each other, or if it's
because of something happening with  the plants surrounding them ...>>

The consensus in horticultural circles is that plants growing in monoculture
conditions, that is all of one kind together--all bearded irises, for
instance--will be more likely to suffer from problems than plants in mixed
conditions. They tend to give each other problems and fungi and things can
spread unimpeded. Separating the plants physically also probably helps. I do
not know of any beneficial companions with iris-specific prophylactic powers.

<< The other possible clue is that all the bare ground in the mixed beds is
mulched.  Maybe it has to do with keeping the soil from splashing up on the
leaves.  I don't allow any mulch in my iris-only beds, but after this year,
I've been wondering if I could. >>

Not mulch per se, Mary, but top dressing thinly may be beneficial. For
aesthetic purposes I cover the soil around most of my bearded irises with a
one chip--not one inch--one chip deep layer of pine bark mulch, keeping it
well away from the rhizomes. I noticed this year before I distributed it that
the soil splashed up onto the leaves much more without it. This very thin
layer does not affect drainage or circulation of air that I can see. I haven't
had much trouble with spot at all. But I also soak every rhizome that comes
into the yard in a ten percent bleach/water solution for fifteen to thirty
minutes, depending on the source. 

Anner Whitehead, Richmond,VA, USDA Zone 7
Henry Hall Henryanner@aol.co,
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