Kenneth Hixson
Sat, 08 Nov 2003 18:36:51 PST
Hi, Carolyn: In addition to Roy and Boyce's remarks:
>I've had some bad experiences with a pre-emergent getting down too 
>deep in the soil and inhibiting root growth
>but I've also had success when 
>I have had sufficient organic matter to bind the pre-emergent very 
>close to the surface. 

	At one time I had a small nursery, and weeds overwhelmed me-especially
at first.  When I considered using a pre-emergent (at that time Casoron for
fall application and Simazine for spring), several things I remembered
caused me
to decide not to use pre-emergent herbicides.

	First, my nursery management professor several times complained that many
nurseries didn't get good results from Casoron because they went elk hunting
when they should have been applying the Casoron--meaning that timing of the
application to catch germinating seedlings before they got too large and 
grew roots below the pre-emergent, was critical.
	Second, I visited one nursery in Washington where after several years
he couldn't grow plants in the ground, in fact even weeds wouldn't
preventing weeds had been his intent, but even his crops wouldn't grow.  He 
finally began to grow plants in containers, as even plowing the soil (turning 
over the top 8") wasn't enough.  He finally sold the property and established
a new nursery elsewhere.  I know he used Casoron, he may have used Simazine,
but I wasn't present when he used either.
	Third, a local nursery here in Oregon growing rhododendrons.  They
applied Casoron around established plants in the ground, and felt that the
plants simply did not grow well afterward.  Even by moving plants to another
area of the nursery that hadn't been treated, the plants did not grow well
for a year or two.  These nursery owners were careful to apply the right
amounts, the soil was highly organic and mulched with bark mulch, and they
felt the Casoron prevented new roots from growing on these older
Note that both of these nurseries were applying Casoron to rhododendrons,
have a fine, fibrous, and shallow root system, as contrasted to something like
the coarse, deep root system of roses.
	Newer herbicides, or different crops, probably would give different results,
but I for one would be very careful to test in small areas before using.

	Ultimately, in my nursery, I did manage to control weeds fairly well without 
the use of pre-emergent herbicides.  It did take time, and the weed
changed, depending on which weed control techniques had been used.  So far,
seems to work for everything, but a combination works fairly well.  Note
that, when
you manage to control one weed, a different weed often becomes dominant, so
changing techniques and herbicides is necessary.


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