By Gay Wilhelm and Trish Grenfell, UC Master Gardeners of Placer County
Q: What can I do to stop crab grass in my lawn?
A: Who hasn’t done combat with crabgrass? But there is help and NOW is the time to take action.
Using a pre-emergent herbicide in mid to late February will help prevent germination of seeds. These are often found in turf grass fertilizers available in garden centers in February. The trick is find the right week in February—but it differs from year to year. The warmer the February, the earlier germination occurs. If you wait too long,
post-emergent herbicides can be used after the crabgrass is established, but it is more effective when the crabgrass has only a few leaves. Be sure to read the label on any pre- or post-emergent herbicides to make sure that the product can be used on your type of turf grass. If the temperature is over 95 degrees, do not use herbicides as the turf may be damaged.
There are two kinds of crabgrass in California—smooth crabgrass and large or hairy crabgrass. Both are spread by seeds and from rooting of the nodes that lie on the soil. AHA! So if you are digging up this pest, you need to be sure to remove all the nodes. Leaving a node is leaving a new crab grass plant.
An important defense is to look at your lawn maintenance practices. Vigorous growing lawns can combat an invasion of crabgrass. Crabgrass is not very competitive. Proper mowing height for your type of turf grass and fertilizing when the turf is growing will help crowd out crabgrass seedlings. Turf grasses adapted to your area will also increase vigor. Watering practices are also important. Overwatering or light daily irrigations can make turf more susceptible to invasions. Infrequent deep watering will lead to a healthier turf.