Lawn Care Blog - Lawn Care Service Blog

Lawn Care Tips - When to Put Down Crabgrass Pre-emergents

Posted by Kathy Wilder

Feb 23, 2011 9:28:00 AM

The perfect time for crabgrass pre-emergents is now!  We’ve crabgrass resized 600had some crazy weather this winter – a blizzard, record-setting snowfall, and freezing temperatures.  Then we warmed up like spring was here.  In fact, temperatures warmed up by 100 degrees in Nowata, OK, within a week – from minus 30 to the 70’s.  That’s a first!  But spring isn’t really here yet, so it’s urgent to get the pre-emergents down before it gets here.  (BTW, if you’re a Fairway customer, this is the application we’re currently doing.)

Crabgrass pre-emergents are essential to the well-being of your lawn, because crabgrass is a nasty, spreading weed that grows great in the heat and can virtually take over a lawn.  Killing it after you see it is much more difficult and requires using material that will temporarily damage your grass.  And, those materials aren’t effective until temperatures are consistently in the 80’s, by which time the crabgrass will have a good start.

Pre-emergents go down into the soil and form a barrier so that the crabgrass doesn’t germinate.  A pre-emergent will not kill crabgrass that is already up and growing.  Crabgrass may germinate when we have consistent weather in the 70’s, and the way it’s been, who knows?

A second pre-emergent application will extend the life of the barrier.  There is some argument that one application is enough, but we have always had the best success with two, and we’ve been doing this for 32 years.  Why take a chance?

You need a post-emergent broadleaf weed control also.  If you’re a DIY, I recommend getting to the lawn and garden store and buying some crabgrass pre-emergent very soon.  But the good thing about having a lawn care company do it for you, is that although your first application of the year is all about the crabgrass pre-emergent, most companies also include post-emergent broadleaf weed control in the application.   And you really need that, because those 70 degree days warmed up the soil, and weeds like chickweed and dead nettle are coming up everywhere!  (Also, lawn care companies have access to materials that are not available over the counter, and their technicians are licensed to apply it properly and safely.)

Other things you can do to discourage crabgrass:  Many things come into play in keeping not just crabgrass out of your lawn, but most weeds in general. 

  • Water deeply and infrequently (twice per week instead of daily) during the summer.  Crabgrass has shallow roots, and will dry out faster than bermuda which has deep roots if you water properly. 
  • Mow properly and frequently.  Download our free mowing tip sheet.

Weed control is ongoing.  Please don’t skip the first pre-emergent application because your lawn looks dormant so you don’t think you need anything yet.  We’d like to say that if you’re on a lawn care program, or if you’ve done it yourself religiously, that your crabgrass and other weeds are gone.  But nature has a way of prevailing.  Weed seeds are everywhere.  They get blown around by wind, carried around by water and squirrels, and pooped out by birds just passing over.  Read more about the nature of weed control.

Note:  Do not put down pre-emergents in areas where you are planning to seed this spring.  Seeding of cool season grass, like fescue, should be done in the fall, but we know people sometimes do it in the spring.  If you use a lawn care company, always tell them when you're planning to seed!

“Preemergence herbicides are the foundation of a turfgrass weed management program.”  -- John Boyd, Professor and Extension Weed Scientist, University of Arkansas

Topics: weed control, crabgrass pre-emergents

Subscribe to Email Updates

Posts by Category

see all