Question
Dear Floyd,
I have just bought a house in Northern California with a large back yard completely covered in dense crab grass. I would like to remove it without spraying. Do you have any suggestions? There are also several fruit trees in the yard whose roots I am worried about damaging while trying to remove the crab grass.

Thank you,
Jessica

Answer
Good morning Jessica:
Crabgrass is a grassy weed commonly found throughout most of the United States. It dies in the fall just before winter, but it drops thousands of seeds before then which will germinate the next spring. Crabgrass will germinate when soil temperatures are greater than 55 to 60 degrees F for 7-10 consecutive days, and continues until soils reach 95 degrees F. Other annual grasses germinate as soils get warmer than 60 degrees. In the mid-west , where I reside, crabgrass usually, but not always, begins germination about the time the Forsythia begin to bloom.
Crabgrass and other annual grassy weeds can be treated through both chemical and non-chemical methods. Your choice of non-chemical requires much patience and a number of years of proper lawn care practices to encourage a dense stand of turfgrass which is the best way to prevent weeds from invading.
Mowing height is very important. Lawns mowed higher (over 2 1/2 inches) tend to have less problems with annual grasses such as crabgrass. Close-mowed lawns allow weeds like crabgrass to invade due to more sunlight exposure in the root zone. This is the reason Crabgrass often invades areas of bare soil.
Shallow and infrequent watering will only weaken the roots of your grass, while allowing the crabgrass to thrive and take over. Water lawns deeply and less frequently. When you water, wet the soil to a depth of 4 - 6 inches. This usually requires the equivalent of 1/2 - 1 inch of rainfall.
When properly fertilized in the spring and fall, a lawn stays deep green, dense and vigorous and a dense turf is better able to resist the invasion of weeds.
Remember that Crabgrass is an annual plant and it will die as temperatures drop in fall.
If after a few years you do not see an improvement you may want to consider preemergent chemical use or even a complete lawn renovation program. If you get to that point let me know and I will guide you.
As far as the roots of the fruit trees are concerned, you will not be able to grow a good stand of grass beneath them as grass does not grow well in shaded areas. You should consider some type of shade tolerant ground cover in those areas under the trees.
Have a good lawn!
Floyd McMahon