Crabgrass

Anyone who has a lawn in Minnesota knows what crabgrass is and how hard it is to completely exterminate from your lawn. Crabgrass is a simple plant in regards to how it grows and survives here in Minnesota , but alleviating it from your landscape will not be so simple.

Biology:
Crabgrass is a warm-season; annual which grows best in the middle of summer when the temperatures are hot. It is not shade tolerant so you will see it congregate along sidewalks or in cracks, on the edge of the lawn by the road or your driveway. The plant winters over as seed and comes up in mid to late- May. The plant itself is killed off by fall frost.

How can I decrease the incidence of crabgrass without chemicals?
Keep a healthy lawn that is made up of a dense stand of grass. Keeping the grass healthy will keep it dense and have less surface area for opportunistic weeds such as crabgrass to invade. Make sure you are using the correct fertilizer and watering program for each season, if not, you could be placing undue stress on your lawn.

Raise your mower height to 2 1/2 to 3 inches during the warmer months. This will increase shade on the soil surface and decrease the chance of the crabgrass seeds from germinating.

Why do I need to apply Crabgrass Preventer in spring?
A spring application of crabgrass preventer destroys crabgrass seeds as they start to germinate which makes them unable to take root and emerge from the soil. It is important to apply this chemical in late April to late May to make sure the product is applied before the seeds have time to germinate. After the seeds have germinated, a pre-emergent (before the plant emerges from the soil), will no longer be effective. Read all directions on the package before you apply. Make sure to always water in your product after you have applied. There are only a select number of products that can be applied along with reseeding, ask a lawn care professional if you have any questions.

Are post-emergent herbicides for crabgrass effective?
There are chemicals that can knock back crabgrass, but not completely get rid of it. These chemicals can be tried when the plant is very young and is not likely to be as successful. Even at this time the plant itself has a very extensive root system and post-emergent sprays will not affect this enough to destroy the plant.