Is there a method to eliminate crab grass at thie time of year, other than pulling the plants manually?
Hello and thank you for contacting Toronto Master Gardeners about crabgrass control .
June and July are the months when crabgrass emerges . It thrives during hot dry weather , grows long purplish flower spikes midsummer to fall , sets seed which disperse by wind, lawnmowers, people and animals walking . The plant (but not its approximately 15000 seeds) is killed by frost .So getting it out now before it flowers ( and those seeds sink into next year’s seed bed where they are viable for years) is the best possible step to controlling it .
There are no chemical controls and no effective organic killer so , the only effective way to rid your lawn of it is to dig it out. This can be a lot of work if you have many weeds but doing it steadily over time gradually reduces infestations . Try using a pitchfork for large areas but otherwise, hand digging each individual plant works. After the rain we have had , this will be an easier job.
Getting the roots is satisfying but not necessary ..it is those seeds we are after. Do not compost the plants and when shaking dirt off the roots , try not to shake the seed heads .
The bright side is that your digging aerates the soil and keeps you in touch with the health of your lawn . Sprinkling grass seed into the holes mitigates the pockmarked lawn though it is likely too hot for the grass seed to germinate right now .
Deterrents : Shallow and frequent watering weakens the roots of your grass while allowing crabgrass to take over, so water less frequently but deeply to a depth of 4-6 inches ( about 1/2 to I inch of rainfall ) .Let the lawn grow to 2 ½ or 3 inches to reduce the amount of sunlight and warmth that reaches dormant seeds .
Thank you for asking us and for being so alert to the health of your lawn . Your neighbours will love you for reducing the neighbourhood seed bed load .