Friday, June 7, 2013

Time to Kill Crab Grass

 Baby crab grass.  No other grass looks or grows like it.

Crabgrass is already starting to sprout as Heron’s Bill sets seed; it’s been a warm spring.  Now is the time to most easily get rid of it.  It is an annual relative of Bermuda grass and has the same kind of flower stalks, with four branches.
 Young Crabrass, flat spreading.  Credit:

Young crab grass, upright and easily pullable.  Credit:

Crabgrass breaks all the rules of annual weeds.  Most annuals are easiest to pull when flowering, because they have shrunk their roots in order to grow their flower stalks.  Crab grass is hardest to pull then, at least if it is well watered; it puts down strong, wiry roots from its stem joints as it flowers, and becomes even more firmly rooted.

Crab grass seed stalk.  Note the resemblance to Bermuda grass.   Credit:

Other weeds are more easily pulled from damp soil.  Crabgrass puts down deeper, stronger roots when it is growing in damp soil; in dry soil, it makes little root, living literally on dust and dew.
Right now, it is about an inch high in bare soil areas with lots of sun.  It’s still waiting to sprout in cooler areas.  Its seeds are fine; they don’t come up through mulch, though they will come up on top of it.  In areas where it is coming up or where you know it seeded last year, it is time to mulch or hoe it out. 
In lawns, an inch of compost will stop crab grass and other small seeds from sprouting, smother small weeds and moss, and feed the grass.  Cut the grass to one inch, cover with compost, and let the grass grow through it.  Keep the grass cut at 2 inches or more to keep weeds from invading.
          On open soil, it comes up thick, but mulch is easier to spread.  Cover it with 2 inches of compost, Walk-on fir (shredded bark-wood mix) or one inch of 4 x 8 sand (1/4-1/8 inch river sand).  (Avoid fine bark; it kills soil life.) 
Cover it with Walk-on, and your work is done.  In the sand, anything that sprouts can be cut or pulled below the crown with a hula hoe (aka scuffle hoe or stirrup hoe) and raked out.  You can use deeper sand, but it feel like walking on a beach.  You can also use the hula hoe on young weeds in bare soil if it is at all loose, but then you have bare soil to track around and grow the little buggers all summer.
          While it is easiest to mulch it out as or before it sprouts, it can be easily pulled until it flowers, and even then if the soil is not watered well.  Not that dry soil is good; other weeds are a pain in dry soil, from which they are hard to pull.
          You can also kill it when it is well-rooted, by cutting it below the crown with pruning scissors.  The roots, while wiry, have no food in them; cut off the plant, and they die in the soil.  This also works on puncture vine and star thistle in dry soil where they do not pull.

Published on Yahoo Voices
Rycke Brown, Natural Gardener        541-955-9040

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