Crabgrass weeds emerge from seeds present in the soil. They sprout when the weather first begins to warm in early spring. It only takes one seed to start a crabgrass infestation. If there is any in your neighborhood you probably are going to get it too.
Seedlings sprout quickly, forming a clump with extensive roots where the soil is moist. Once established, it is difficult to weed out because of it roots at each node. These are called tillers because they, in turn, put down additional roots along their length and the process repeats exponentially. A single crabgrass plant’s root system can easily stretch nearly 4 feet in any direction. One plant will create a thick mat of both visible top and invisible root growth, which eventually smothers lawn grasses.
Growth is slow during spring months, by June the plants are producing their tiller roots and shoots; and flowering by late July and August. Once started, germination continues throughout the summer and into fall. Prior year crabgrass that did not die off from winter frosts may even produce new growth and a second crop of seed in spring or early summer.
Obviously, once infested, the important thing is to control the weed before it sets seed or you will have tens of thousands more seeds that can remain a threat for up to 3 years. The next spring they will sprout and the vicious cycle begins again.
In short, crabgrass seeds from up to 3 years earlier are probably sitting in your lawn even as you read this, just waiting to infest your lawn all summer long. Once the soil temperature (not air temperature) reaches the 50-to-55 range for at least 7 to 10 days in a row, their seed dormancy will end and they will germinate for up to six weeks.
Because crabgrass loves hot sun-baked open spaces and has tremendous growth, survival, and reproductive capabilities it is especially hard to fight here in our Valley. To succeed you must seek it out, not only in your lawn; but also in adjacent places such as cracks in sidewalks or along the edges of a driveway, etc. This will involve mulching, hoeing, and pulling when the plants are young and before they seed. If this all sounds like a lot of work – it is!Prevention Is Better Than Cure
Prevention Is Better Than Cure
Prevention is faster, cheaper and easier than cure, and timing is everything. Your first and best line of defense is to stop the crabgrass seeds BEFORE they sprout.
You can do some of this by mulching. However, be careful – mulch that has lain undisturbed in the soil for a while can actually provide an adequate growth medium for weeds. To stop weed seedlings germinating in your mulch, it is important to move the mulch about periodically with a rake to prevent their establishment.
In most cases, mulching alone will not do the job and should be supplemented by a pre-emergent weed control that prevents the seeds from germinating. But there is a very narrow window because pre-emergent herbicides must be applied one to two weeks prior to crabgrass germination, which will occur here in our Valley within the next few weeks – so NOW is the time to move on this.
Alden Lane Nursery recommends Bonide Crabgrass Preventer with Fertilizer – A granular lawn fertilizer containing a premium pre-emergent weed killer which controls Crabgrass, Foxtail, Goosegrass, Poa Annual and other annual grasses in established turf lawns and landscapes.