Fall crabgrass control is pretty much limited to the normal die back in the fall. There are several products in the market that are labeled for post emergent control. One of the products labeled for post emergent crabgrass control is Q4. Q4 has a broad spectrum of weeds that it controls. The product costs quite a bit more than your average weed killer, but it will definitely do the job. Depending on the extent of the crabgrass in your lawn, you might have to apply the product several times for full control. The best time to use a product such as Q4 is when the weed is actively growing. If you treat in the fall after a hard frost, you are probably wasting your time and money.
Fall crabgrass control natures way.
When you are seeking fall crabgrass control for your lawn, it is best just to let nature take its course. You probably have an out break of crabgrass if you neglected to apply a pre-emergent product in the spring to your lawn. Since fall is here, the best thing to do is just let the crabgrass in your lawn die out naturally. If you live in a cooler climate, crabgrass will start dying out when night-time temperatures get down in the 30’s and 40’s. By now the damage to your lawn is already done and fall crabgrass control won’t do much to save your lawn. If you have had quite a bit of crabgrass in your lawn this year, you probably have quite a few seeds left behind in the process. An average yard hold tens of thousands of weed seeds just waiting to germinate. obviously all of those seeds do not germinate, but they may stay in your soil for quite a few years to come.
If you want to keep your lawn crabgrass free, apply two applications of pre-emergent crabgrass control in the spring about a month and a half apart. If you start to see a crabgrass out break after you have applied both rounds of pre-emergents, consider post emergent control with a product like Q4. If your lawn is in pretty rough shape, it may take several years of quality weed control applications to give you the results that you want.