The introduction of crabgrass into a yard can be a difficult thing for many homeowners to deal with. Though the grass can be unsightly and even take over broad sections of the yard, a number of options exist for dealing with the grass. These options are based not only on looking at how the plant behaves, but its general characteristics and development. Such issues can point to the most opportune times to act against this invasive species.
One of the most important things to realize about the treatment of crabgrass is that the grass is an annual. No matter how much crabgrass you see this year, the grass that appears next year is not the same. It cannot winter over, and dies. Before it does so, however, it produces seed. This seed can be stopped the next year by applying a pre-emergent herbicide before the soil reaches a temperature of 60 degrees or more consistently.
Crabgrass is native to Europe, but has shown itself very adept at finding a foothold in the lower 48 United States. However, while the grass has proven itself to be very adaptable to different soil conditions and climates, it is not considered a very competitive grass. Therefore, keeping other grasses healthy and full will often choke out crabgrass before it can get a start.
A number of treatment options exist for getting rid of crabgrass. One of those, a pre-emergent herbicide, has already been mentioned. But there are others as well, including post-emergent herbicides and blocking the access to sufficient light. Each has its advantages and disadvantages.
For those considering using a post-emergent herbicide, remember that such products will not only kill crabgrass, but could also kill desired grass species in the yard. Therefore, be prepared to re-sod or re-seed in such cases. In some warmer environments, crabgrass may never completely disappear at the end of the summer or fall as it does in some cooler climates. Therefore, a post-emergent herbicide may be one of the few viable options.
The best potential solution to the problem is to deprive the crabgrass of light. This can effectively defeat the grass with no other harsh chemicals. In order to deprive the crabgrass of light, using trees and planting shade tolerant grasses is a good idea. Also, just maintaining the proper mowing height of your desired grass should shade the immature crabgrass and prevent it from growing. Such solutions are cost effective and do very little additional harm.
It may also be possible to use post-emergent herbicides on crabgrass in situations where the grass is still small enough for spot control. However, over large areas, the post-emergent herbicide may be ineffective. Direct intervention, such as weeding, can also be tried, but this can be a very labor intensive pursuit, especially if areas of crabgrass are very large.