Garden Detective: Crabgrass needs diligence to make it disappear

Where can I find out information about crabgrass? It is really getting out of hand in my backyard in the lawn and around the little garden area.

About two years or more ago, it all started. I have tried all the Bayer and other grass weed killers. But to no avail; it just keeps thriving.

I have tried to pull them out around the garden but the roots still survive. Help!

Ed Diaz, Dixon

According to the UC master gardeners, crabgrass spreads primarily by seed. Crowd out the potential for crabgrass by increasing the vigor of your lawn.

The UC Guide to Healthy Lawns, available at, has detailed advice on lawn care. Mulching, hoeing and hand-pulling when plants are young are all effective cultural methods to control crabgrass invasion.

If using herbicides, be ready to apply them in late winter. Pre-emergent herbicides for crabgrass control in turf areas need to be applied during the last week of February or first week of March.

To be effective, the herbicide must be applied before the crabgrass germinates. In Central and Northern California, crabgrass begins germination around March 1 to 15 when soil temperatures reach 50 degrees to 55 degrees for at least three days.

If you have a heavy infestation of this pesky weed, it might be advisable to re-apply the pre-emergent again in late June.

If you still have crabgrass during the summer and fall, you can spot-treat it with a product made for crabgrass control such as Monterey Weed-Hoe, manufactured by Monterey Lawn and Garden Products of Fresno. Ortho has a similar product. These herbicides will kill only the crabgrass, not the lawn grasses. If you use these products, make sure to apply it before the crabgrass forms seed.

You can learn more in the Cooperative Extension’s Pest Note 7456, devoted to Crabgrass. You can find this pest note online at . Or send a self-addressed, stamped, business-size envelope to: Pest Note No. 7456: Crabgrass, UC Cooperative Extension, 4145 Branch Center Road, Sacramento, CA 95827.