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CULT: Irises and Boron

Bill Shear writes:

<< I see an urban myth in the making: leaf spot is caused by boron
 deficiency--I read it on the internet!  >>

I think most people are capable of recognizing a speculative thread  for what
it is and are sane about repeating such speculation, especially if the
speculation, or exploratory discussion if you prefer, arose from an
observation in an older source. I think they also know that an unfaded cover
is not the only measure of a publication's worth and it is precisely because
our knowledge changes and more sophisticated scientific information becomes
available to us that we may find it useful from time to time to reeximaine
older observations about things. These are not invariably sound, but neither
are they invariably unsound. 

Now, what anybody on this list read from my original posting was that in 1947
the American Iris Society, in THE IRIS: AN IDEAL HARDY PERENNIAL published the
suggestion that boron levels might be checked in relation to leaf spot. This
information was included in an article by Geddes Douglas called "The Fourteen
Points of Bearded Iris Culture", which is very measured in tone and remains
useful today. The article was based on resposes to a survey sent out by AIS to
eighty-five experts "scattered across the whole country", this reflecting the
thought that "there are several radically different climatic-geographical
areas in the United States". Here is the entry:

<<Question No. 13, What treatment do you recommend for leaf spot? drew these
1. Cut off diseased portions and burn.
2. Spray with lime-sulphur solution in spring.
3. Spray with Fermate
4. Check boron deficiency in soil.>>

As I have followed the discussion, Dr. Shear informed us that while boron is
an essential trace element for plant life, deficiencies are rare. At which
point Dr. Mann informed us that boron needs vary from plant to plant and less
than optimum levels for some agricultural crops are found in differing areas
and soil types throughout the country,  including her own. She proposes to
investigate the matter further.  We apparently have no data about the boron
requirements of bearded irises, but we are told that the line between adequate
boron and toxic boron levels is a very fine one, and it follows that, if we
don't want to risk hurting the garden, a good soil test is, as always, advised
before treating with boron, or any other soil amendment with the possible
exception of compost. 

I thank all of you for the information on boron, which I solicited. I wish I
understood soil science better, but I am learning. For what it may be worth
the very worst spontaneous outbreak of fungal leafspot I have ever seen was
throughout a very large monoculture (tilled) planting in acidic sandy soil in
a rural area following a period of highly unsettled weather involving
unseasonable high temperatures, heavy rain, and a hailstorm which caused
physical damage to the leaves. This planting is otherwise meticulously grown
and treated.

Anner Whitehead, Richmond,Va
Henry Hall henryanner@aol.com


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