Defeating Crabgrass

defeating crabgrass potential main photoIn the effort to have a healthy lawn, crabgrass can be a tough opponent. This weed gets its name from the way that it sprawls from one central root across the ground, keeping a low profile like the invader that it is. But if you are armed with some knowledge, a plan, and the right weapons, this stubborn rooting grass can be beaten.

In this blog post we will cover:

  • Overview of Crabgrass
  • Lawn Maintenance
  • Crabgrass Prevention


crabgrass along drivewayCrabgrass is a warm-season annual weed.  The good news is that this means that you have a fresh chance to stop it EVERY spring! It is native to Europe but was imported to North America as forage. It thrives in areas that absorb heat, such as right next to driveways, curbs, sidewalks and south-facing slopes. Crabgrass grows very quickly in hot, dry conditions. It loves compacted soil and clay. It usually forms into mats that smothers more desireable grasses and more often than not steals nutrients.

Crabgrass reproduces by aggressively spreading its seed all over your lawn. It germinates in the spring once the soil has warmed up to 55-60 degrees for at least a week. The weed grows through the summer, produces seeds and drops them, then dies off with the first hard frost. In fact, before dying in the fall, a single weed can distribute thousands of seeds which will germinate in the following spring.


fertilizer spreaderThe best weapon you have against crabgrass is a thick, healthy lawn, which will provide a dark canopy of grass blades over any crabgrass seeds and prevent them from sprouting. There are several things that you can do achieve this.

Reduce Soil Compaction: Compacted soil deprives grass’ roots of the air and water circulation that they need. In their place, weeds will thrive. Running an aerator, like those that Koopman Lumber rents, over any compacted soil areas to loosen them up.  A word of caution though – when you aerate, you are also pulling up dormant crabgrass and weed seeds and spreading them on the top of the soil where they want to grow.  So always treat for crabgrass when you aerate, regardless of the time of year.

Mow High: Grass should typically be mowed to the maximum height your mower allows. This will allow the lawn grass to protect its turf more successfully against weeds. Also, be sure to keep your mower blades sharp so that they cut the grass cleanly instead of tearing it. Like most plants, lawns grow best if you clip off the growing points and allow the grass to branch out and become denser. Koopman offers sharpening services to keep your mower cutting at its highest performance level.

Water Thoroughly: To encourage your lawn to grow a deep root system, water thoroughly once a week. This will make the whole lawn hardier and heat tolerant. Short, frequent watering only promotes shallow, weaker root systems.

Reseed & Overseed: Thin or weed-damaged areas should be reseeded in the fall. The warm days, cool nights and morning dews make this the best time of the year for putting down grass seed.


If you haven’t done the kind of maintenance we just discussed, or if your neighbor hasn’t and seeds from his crabgrass spread to your lawn, there are preventive steps you can take to deal with the crabgrass waiting to germinate and take over your lawn.

Most importantly, you want to treat the lawn before the crabgrass seedlings sprout. You can do this by applying a pre-emergent treatment, which is a crabgrass preventer, in the spring. This treatment creates a barrier at the surface of the soil. As the seeds begin germinating, they take in the herbicide and die. Understanding this is important to remember for two reasons:

1. First, doing anything to puncture this barrier will defeat the purpose. This means that you need to do any raking, dethatching or aerating before putting down crabgrass preventer.

2. Second, the same herbicides that kill off crabgrass seeds will also kill off any grass seed that you put down.  So don’t put down seed and traditional “Step one” fertilizer together.  One solution is to take care of controlling the crabgrass in the spring, then do any seeding in the late summer or early fall. Make sure to wait at least eight weeks to seed after putting down crabgrass preventer.  The other is to use a product like Jonathan Green’s Crabgrass Preventer Plus New Seeding Fertilizer, which allows you to apply grass seed on the same day.  It is a selective herbicide meaning it will only kill the crabgrass, not the good grass.

Applying at the proper time is essential because the window is short. The ideal soil temperature for crabgrass preventer is 52 degrees Fahrenheit. The best way to know when crabgrass is ready to germinate is by watching the bright yellow forsythia plants.  When they are in bloom, put down Step 1 – or crabgrass control.  One of the big benefits of Jonathan Green’s crabgrass control is that it has both a PRE and POST emergent control.   That means that it will kill crabgrass seedlings even AFTER they sprout.  So if you’re running late – go with Jonathan Green.

Once finished, make sure to sweep any fertilizer that landed on any hard surfaces back into the lawn.

Even still, you may get some young crabgrass plants popping up in your lawn. They should be pulled out as soon as you see them. They will only leave a small hole in your turf which desirable grass types can quickly fill. If you wait too long and the crabgrass matures into a full seed head, pulling them out will leave a larger hole in your lawn and allow thousands of seeds to spread. At that point, it’s better to leave the plant alone since it will die in the fall.

Another option is to spot-treat problem areas by spraying them with a post-emergent herbicide. This option is effective at eliminating immature crabgrass that has not yet gone to seed. Post-emergent herbicides are usually applied with a hand pump sprayer. This is best to do on a hot day where there’s very little wind. Temperatures that are too low will make the product ineffective.  As when using any chemical, be sure to wear safety gloves and eye protection. We recommend keeping a small bottle handy and just walk the lawn every few days and fire away at new sprouts.


By following these steps, you can reclaim your lawn from the scourge of crabgrass!  Here at Koopman, we have the tools and treatments you will need, from crabgrass preventers to pump sprayers and fertilizer spreaders to garden hoses and lawn sprinklers.  Combine that with our know-how and you’ll be equipped with everything that you’ll need to battle crabgrass and win!  When you start with good seed and keep building up the soil, you’ll soon have a great canopy of green grass that will be much easier to maintain in the long run.

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