Crabgrass has been the bane of landscapers and lawn enthusiasts since the first yard appeared. The fancy, scientific name for the most common crabgrass found in North America is Digitaria sanguinalis. This weed is sometimes called finger-grass because the stems where the seeds develop shoot off from the main plant and look like, well, skinny fingers. So, the question becomes how to get rid of the weed before it can get a toe-hold, or, in this case finger-hold, in your yard.

A Bit More Science

Crabgrass grows best in direct sunlight in lawns that are watered very lightly. It also thrives in under fertilized, poorly drained lawns and areas where the grass is particularly thin. It's an annual plant that develops from seeds distributed the year before. The scary thing is one plant can throw off over 150,000 seeds before fall frost kills it off. The main plant can grow up to twelve inches in diameter and, when it dies, can leave huge holes in your lawn that are perfect for the next generation of the weed to develop.

Generally, the crabgrass seeds are dropped in the fall and sit in your yard as a seed through the winter. In the late spring or early summer, the seeds begin to germinate and grow very quickly. They can outgrow most types of grass and vegetable and can take over a yard or garden by pushing out the more desirable plants. As the seeds begin to germinate, they produce an enzyme that is crucial to the plant's development. The importance of this enzyme will become clear a little later.

What Can I Do?

A full, lush lawn is the best way to keep crabgrass out and good grass in. As time passes, the soil in your lawn gets packed down tighter and tighter. A light aerating in the spring can help open up the soil to allow water and nutrients to reach the roots of whatever grass you grow. If the soil is already really hard and compact, you may want to think about hiring a professional to come out with a piston driven aerator to really loosen up the soil. You don't need to hire a professional every year, but it may not be a bad idea every five to seven years. Fertilizing your yard can also help provide the grass with much needed nutrients so it can grow and thrive. During particularly dry years, a good watering plan will help the grass stay healthy, too. Get some grass seed into areas that are really thin or bald, especially areas that see sun all day long.

Proper mowing also helps the lawn stay healthy. Most grasses grow best at about two and a half to three inches long. Not only does this let the blades of grass grab enough sunlight for photosynthesis to occur, it shades the soil underneath the grass. When crabgrass gets its start, it is low to the ground and, if the sun can't reach it through the grass, it won't be able to grow.

If you mow your grass before it gets too high, leaving the clippings in the yard is a good idea. As the clippings decompose, they return the nutrients back into the ground, where they do the grass the most good. Also, alternate your mowing patterns. If you can develop four or five regular patterns and alternate them throughout the spring, summer and fall, your grass will stand up straighter and you can avoid those unsightly ruts that happen when the tires of your mower pass over the same area again and again.

Herbicides

Every yard, no matter how well maintained, is still going to have areas where crabgrass can grow and thrive. Along sidewalks and in the cracks between the sections, next to landscaping features and near the foundations of the house are all places that crabgrass grows. It can also show up in the landscaping where whatever groundcover you use, pine needles, bark or stones, gets thin. In these areas the best way to combat crabgrass is a pre-emergence herbicide.

Do you remember the enzyme I mentioned above that is important to the seed's germination process? Most of these herbicides block the production of the enzyme, stopping the growth process. Timing is critical, though, in the application of the herbicide. If you put it on too early, the herbicide will sink too far into the soil before the seeds start to sprout and miss out. If you put it on too late, the enzyme will already have been used and the herbicide will do no good. Different parts of the country, with different weather patterns, are going to vary in the best time to apply an herbicide. Make sure to check with your local lawn and garden center to find out how to tell what the best time is going to be in your area. Also, make certain to follow the directions on the container, as well as any warnings. It is possible that these herbicides can be bad for other plants, as well as for humans and animals.