[Arid_gardener] Fw: When to apply Pre-emergent herbicide?

[Olin Miller]

----- Original Message ----- From: "Olin Miller" <olindmiller at att.net>
To: <User536444 at aol.com>
Sent: Monday, August 27, 2007 2:44 PM
Subject: When to apply Pregent herbicide?


>I believe your landscaper is pretty close.  But you might want to wait 
>until
> the seeds ripen and drop from the plants
>
> We often think of weeds as cool season and warm season.  But there are 
> also
> some that don't seem to care about the season.  There is some thought that
> warm season weed seeds germinate in the spring when the daylight and
> darkness hours are equal (12 hours) and the cool season weeds germinate in
> the fall when daylight and darkness hours are also equal.  Ideally, this
> would occur at the vernal equinox (1st day of spring - March 20) and the
> autumnal equinox (1st day of fall - September 22).  Thus pre-emergent
> herbicides should be applied around March 1 and September 1, well  before
> germination.
>
> To be more precise, the 12 hour light/12 hour dark dates are more like 
> March
> 18 and September 26 because the earth's atmosphere bends the sun's rays
> enough to make them visible on the earth on those dates..
>
> I don't believe there is much in the way of scientific evidence that this
> system works but, hey, it is a system.
>
> Note:  This information is from my personal experience and observations 
> and
> should not be construed as a recommendation from the U of A Cooperative
> Extension Service.
>
> Olin Miller, Master Gardener Volunteer
> U of A Cooperative Extension, Maricopa County AZ
> ============================================
>
>
> ----- Original Message ----- From: <User536444 at aol.com>
> Sent: Monday, August 27, 2007 6:57 AM
>> ...
>> ...  when is the
>> best time to spray to prevent the germination of weeds?  The  landscaper
>> says
>> now but the weeds are in bloom.  It seems that there is a  time of year
>> when
>> if sprayed, they will not grow.
>> ...
>> Juanita Guidry Copeland
>