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Question: Last year my lawn was filled with crabgrass. What is the best way to get rid of it?
Answer: Crabgrass is one of those notorious weeds that everyone thinks they have in their lawn. Lawn care companies and chemical manufacturers use it to promote their products. In reality, most people probably don't have crabgrass itself, even if they do have a weed problem of some kind. One of the first rules for all methods of getting rid of a nuisance is to be sure of its identity before attempting any remedies. Crabgrass control is no exception to this rule. Crabgrass is an annual plant type. This means that it lives for a season during which it blooms, produces seeds and then dies. Even if you don't get a cold winter in your area, it still dies. For everyone in cold winter areas it will die with the first frost in the fall. If you think you have crabgrass and you see it during the cold weather months, you don't have crabgrass and you must figure out what you do have before you waste your time and money (and potentially harming the environment) throwing chemicals on your lawn. Tall fescue is a clump forming grass that is noticeable in the spring when crabgrass is still in its infancy and not readily visible in a lawn. Tall fescue is a perennial that is completely immune to crabgrass controls. Even if I could put pictures of crabgrass in your newspaper, it would still not be easy for most people to look at the picture and be positive of identifying the same plant in their lawn. Even descriptions that crabgrass has short leaves that taper to a point and are sparsely hairy don't help too much. The best method of identification is to have someone who knows what it really looks like show it to you. Unfortunately, that is after the best time to treat your lawn to prevent its growth. There are several steps to preventing weeds from growing in a lawn. The first is to have a healthy lawn of good grass plants. The second is to prevent the weed's growth and the third is to kill it after it is in the lawn. Let's start with the second step because that is what most people want to do in the spring each year. They will see numerous advertisements suggesting that they need to use a pre-emergent on their lawn. Pre-emergent weed killers are typically an excellent method to controlling weeds and a huge waste of money if you don't have the weeds. A single crabgrass plant can produce over a thousand seeds in it short life. About half will sprout the following year and about twenty-five percent the next year and after a few more years they will be gone, except for a few that could sprout many years later. If you can prevent five hundred new crabgrass plants from sprouting, you have prevented thousands of their seeds from growing too. Crabgrass seeds are known to begin sprouting only after the soil temperature stays above 55 degrees for five days in a row. They can continue sprouting for more than two months. Crabgrass prevention chemicals need to be applied to the soil before the soil warms up to the 55 degree level. Some chemicals do not last for more than a month or two, so if the chemical is applied too early it will be less effective on late sprouting seeds. Some pre-emergent chemicals also work post-emergently. They will still be effective after the seeds germinate. Typical pre-emergents should be applied about the same time as forsythia flowers are finishing up and before lilacs begin blooming and about the time dogwood trees are in bloom. There are many brands of crabgrass controls and different formulations of the chemicals in the products. For effective control of crabgrass, you must follow the directions on the package. Using too much or not enough and applying it at the wrong time will all cause it to be less effective and possibly even harmful to your lawn and its surroundings. Different portions of your lawn may warm up sooner depending on the sun and shade areas created by trees and buildings. After a pre-emergent has been applied, do not disturb the soil surface. The chemical barrier must remain or else some seeds may sprout and not come in contact with the chemical. You can not aerate the soil, de-thatch the lawn or use a slit seeder because they all ruin the chemical barrier. You can not add good grass seed for several months after applying the pre-emergent because it will prevent good grasses from sprouting too. Once your lawn has not had crabgrass for several years, you should not use a pre-emergent for a problem that no longer exists in your lawn. You can wait until it shows up and use a post emergent to eradicate it during that season and if you desire, you can use a pre-emergent the following year. Post-emergent weed killers are often less effective on weeds. Following instructions is very important for effective results. Crabgrass seeds (and other weed seeds too) sprout better in thin bare areas of soil. They get the sunlight and warmth they need. If the lawn grass is thick and full, there will be fewer weed seeds sprouting. Mow your lawn at the proper height for the species and only take of about one-third of the grass blade during each mowing. Water and fertilize it properly and it will remain healthy with fewer weeds. |