[permaculture] crabgrass eradication

Dieter Brand diebrand at yahoo.com
Sat Jun 23 09:41:52 EDT 2007

  I know that crabgrass goes dormant in fall and starts growing
  again when the weather gets warm in the spring, but I was of
  the opinion that it grows from the rhizomes, apart from
  the seeds that is. I can’t really proof this, but when digging 
  out rhizomes from my vegetable garden last March, the green
  blades had only just shown above the surface, while a large 
  network of rhizomes reached at least 1 foot underground 
  with older pieces which had gone almost woody. It would 
  have been impossible for the rhizomes to grow in the few 
  warm days we had until March. And there is no reason 
  why the tiny seeds should germinate at a depth of a foot 
  or more. Perhaps, the difference can be explained by the 
  climate. We only occasionally have light nighttime frost
  in the winter.
  By the way, referring to an earlier post of yours, it is quite
  easy to dig out crabgrass from loose garden soil if you 
  use a spading fork (if that is the term used in English, it is 
  called Grabgabel in German) to loosen the soil near the 
  crabgrass, then you can carefully pull the whole bundle 
  of rhizomes out of the ground at one go. Never use a spade. 
  A spade will cut the rhizomes into smaller pieces which will 
  each grow into a new rhizome.
  Dieter Brand
  Steve Diver <steved at ipa.net> wrote:
  Dieter - 

Crabgrass is a warm-season annual that comes back from 
seed. It re-seeds heavily. It sprouts and grows rapidly
each week during the warm part of the growing season, after
the cool springtime.

It seems like you get a bunch of good work done on the 
farm and garden and everything looks clean, then you turn 
away to other chores and when you look back..... it's 
jumping out of the ground.

It depends on your cropping system and local situation.
Mulches are excellent for small-scale production. Cultivation
is common in broadscale. Thermal weed control (flame) will
nip young seedlings in combination with cultivation. Weeder 
geese were used to control annual grassy weeds on hundreds 
and thousands of acres of broadacre crops back in the 1940, 
50s, and 60s. The aim is to nip them at seedling stage. 

Paul -

Yes, green chemistry herbicides that include acetic acid,
citric acid, and other natural ingredients that act as
dessicants will nip crabgrass. 

I've got "before" and "after" photos of 20% acetic acid working
on grassy weeds (like crabgrass), broadleaf weeds, and nutgrass.

It knocks back broadleaf weeds real hard, sometimes completely
in one application.

It knocks back grassy weeds about 75%, then you have to 
come back within a week and hit them again, where the
effect goes up to 95%. But grasses have those growing
points that are hidden from spray solutions, so they
re-sprout.... which means you'll normally have to repeat
applications a few times during the growing season.

Folks, keep in mind that "eradication" of weeds is the 
mindset of chemical agriculture. 

These green chemistry herbicides will knock back and 
"suppress" weed growth, but not necessiarly "kill" 
the weeds outright. But that is often quite sufficient. 
The weeds are set back and no longer competing with the main
crop or resulting in a jungle of weeds. 

Once you get a crop up to canopy, weeds are shaded out 
fairly well which also suppresses their growth.

Steve Diver

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