So what is up with crabgrass? Well, it is an annual summer grass. It likes the hot stressed out areas of your lawn the best. The areas of your lawn that are trimmed with a string trimmer are usually cut lower then the rest of the lawn. Pavement, rock beds, walls, a foundation or even the South face of an evergreen shrub reflect heat back on the lawn. The competing lawn doesn't like it. The crabgrass not only doesn't mind the heat, it likes that lack of competition.
A few technical facts about the weed. Crabgrass begins to germinate when the soil is about 55 degrees. Another thing happens at about this soil temperature too, Forsythia blooms. Do you know Forsythia? It is that shrub with straggly twigs, bunching up from the ground. It has yellow flowers on it early in the Spring. It blooms before it has leaves on it. It must be the first shrub to bloom and it is more often planted at the older homes in town. When we see Forsythia blooming we know crabgrass is getting it's start, even though we can't see it yet. Crabgrass is an annual plant. That means it germinates, reaches full growth produces seeds and dies all in one season. Its whole life cycle is lived in one season. This means crabgrass can only start it's life from the seeds that were dropped by the weeds the summer before.
I could have probably skipped telling you all about what it likes and how its life goes and just got right to how to kill it. That is what you really want to know. Well, how to get rid of this pest is all answered in it's life cycle.
First, the natural and obvious way - pull it when you see it. This prevents next season's seeds. Keep the competition strong! Be careful not to mow too low or do your trimming too low. Fertilize, aerate and practice good watering of your turf lawn. Crabgrass doesn't like your strong lawn it likes the weak lawn areas. A healthy lawn is 90% of the fight.
Secondly, you can use a pre-emergent herbicide. These can give good control but timing is the key. Pre-emergents don't kill seeds or growing plants, they kill germinating seedlings. (A word of caution - don't use them if your seeding a new lawn.) One thing that can be hard about the timing is that the soil on the North face of your home is a colder than on the South. It warms up at the edge of the road quicker than in the shade. Cool dry Springs set back the germination time. Germination is earlier in years with wet warm Springs. Use the pre-emergent according to it's labeling. Do not over use the product this can cause damage. If the label allows consider putting it over the entire lawn at half the recommended rate early in the Spring and another half rate mid-spring. Say at about the beginning of April and then again about mid-May. Never going over the total maximum application rate. Sweep granules off the side walk with care, don't use a leaf blower and blow it far from the edge that the crabgrass loves. Then water in the product according to the label. If you are using the product before your sprinklers are turn on for the season, time the application just before rain or snow.
You can use post-emergent herbicides too. These crabgrass killers really only kill crabgrass when it is young. By the time you see two to three of those branches out of the first branch post-emergents won't really work anymore. When you see a well established plant pull or dig it out. Remember it is not coming back from that plants roots in the next year, only it's seeds.
One final tip, don't pick out and try just one of these controls - combine them all. To get the best results use all of your tools, a holistic approach. If you want to control crabgrass without the use of herbicides, pull it and keep your lawn very healthy. It will be more pulling work but you will get reasonable control over it.
Longmont yard care