On Aug 21, 11:30 am, z wrote:
On Aug 21, 6:01 am, Eggs Zachtly wrote:





Richard Thoms said:

Quote: JL wrote on Thu, 16 August 2007 23:28
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I had a section of lawn that had crabgrass in years past.
This spring I used a product that contains Dimension (thanks ahlg).
It worked great. I have some stray crabgrass plants
that I deal with spot treatment.

Will I ruin my Dimension for next year if I de-thatch
this fall/next spring? That is, how long do I have to
wait for the crabgrass seeds to finally die before I'm
able to dethatch?
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I'm just curious. Why would de-thatching interfere with the pre-emergent?

The pre-emergent creates an invisible "barrier" that the weeds can't poke
through. Any distruption of that barrier renders it useless.

--

Eggs

Two can live as cheaply as one, for half as long.

Hmm. That's what about.com says as well.http://landscaping.about.com/od/weed...crab_grass.htm
I'm a little surprised; I don't know about the commercial stuff, but I
use corn gluten as a preemergent, which just inhibits root
development, so I never thought about whether "puncturing" it would be
a problem.- Hide quoted text -

- Show quoted text -

It's the same concept. Neither one forms a physical barrier that
crabgrass can't grow through. What they do is establish a top layer
of soil that crabgrass can't germinate in. If you disturb that layer
by dethatching, aerating, etc, you lose the protection.