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Bob,
Thanks for all the information. Living further
south, we deal with nut sedge, which is not affected by any of the
compounds you mentioned. I use Manage (Monsanto), which is labeled for use in
turf grasses. Generally, the sedges are warm weather weeds and the first
application is long after Siberian bloom.
Dennis Hager
on Delmarva
----- Original Message -----
From:
c*@cablespeed.com
To: s*@yahoogroups.com
Sent: Monday, July 19, 2004 10:20
PM
Subject: Re: [sibrob] RE: Roundup and
other herbicides
Like a lot of other people we use Roundup (2.5 oz/gallon)
all year round in
the Siberian beds (though always trying to avoid direct
contact of the
spray with the irises). Every year a handful of flowers
show the pale
colors and changed form typical of Roundup injury, but I've
never seen the
vegetative parts of a plant much affected or had one die,
so there is some
degree of resistance which is a blessing. Here are a few
more observations
on herbicides and Siberians:
Snapshot (2.5%
granular) is a pre-emergent herbicide mixture - a sort of
improved version
of Treflan. We use it very widely around the new seedlings
and it has
never caused any problem. As long as it is rained or hoed in
soon after
application, it does a great job. Poast (common name;
sethoxydim) is a
grass-selective compound. I never saw any problems with
Siberians
oversprayed with this. However, a few years back I switched to a
closely-related compound Select (clethodim) because it is supposed to
control annual bluegrass which Poast doesn't. This was a mini-disaster.
Sprayed on the plants while they had bloom stalks, it blasted every bud -
they just dried and withered. Fortunately it was used on a very limited
area. The plants themselves weren't killed, but it was a nasty surprise
and
the last time I used Select. Not entirely grass-specific, whatever the
claims! The last grass-specific herbicide that we use now as a primary
compound is Fusillade II (fluazifop-P-butyl). This seems to be pretty much
harmless to irises, though I haven't sprayed them when in bloom. Lastly, a
really useful compound is Lontrel (Stinger; common name: clopyralid))
which
is a plant hormone analog like 2,4-D. It works wonders on thistles
and
compositae like dandelions and ragweed and a few other significant
weeds.
It doesn't seem to harm the irises but it does cause twisting of
the flower
stems so it shouldn't be used when they are in bloom. With
care, you can
get just about every weed with these compounds. But, these
mixed
experiences do clearly show that the flowers are often the most
sensitive
part of the plant and that, as Harold says, some initial tests
on a limited
area before believing anything you read or are told can save
some grief. It
would be interesting to find out how other people with
large plantings
handle weeds. Weed pressure is relentless and makes most
of the work in
growing Siberians for us. Bob
Hollingworth
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