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| MN Lawn Care Tips Tips for Creating a Beautiful Lawn in Minnesota |
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Dethatching
and Aerating Lawns
by Bachmans.com
Dethatching and Aerating Thatch buildup and soil compaction are conditions that cause lawns to struggle. When severe, they can ruin a lawn. Luckily, both problems can be resolved. Simply dethatching or aerating the lawn will provide an immediate fix, but it is also important to find out what the contributing factors are and make some changes so that the solution will be long-term, not just temporary. All About Thatch Thatch is a layer of debris, made up mostly of grass clippings, that accumulates above the soil and below the blades of grass. This isn't just a layer of freshly cut grass clippings. To see it clearly, simply dig out a scoop of your lawn (don't worry, you can put it right back when you're done) and look at it from the side. You should be able to identify the soil, the thatch and the top growth of the lawn grasses. The thatch layer will look like a tightly knit layer of brown debris. While thatch is primarily composed of cut grass blades, it also contains the bits and pieces of leaves and twigs that have fallen onto the lawn. In a healthy lawn, the thatch layer will decay naturally, providing nutrients for the lawn. A healthy lawn will have a layer of thatch about a half inch thick. Having no thatch layer isn't the goal either, because that can open the lawn to drought and heat stress. Thatch not only provides nutrients, it also helps shade and protect the crowns of the grass plants and helps conserve moisture. Lawns with a healthy layer of thatch do not need dethatching. Sometimes the lawn can have too much thatch. Excessive thatch happens when the lawn is fertilized too often, the grass clippings are too long, or there aren't enough of the microorganisms that digest the thatch present. Most often, it is a combination of these factors. When the thatch layer is too deep (in excess of a half inch), the lawn will begin to thin. Lawns with heavy thatch tend to have a shallow root system, making it harder to maintain the grass. Thatch can keep water, air and nutrients from getting to the roots. Also, lawns with excessive thatch are more likely to have problems with diseases. All About Dethatching Dethatching removes excess thatch. It is best to dethatch the varieties of grass grown in our area in early fall. (When lawns are dethatched in spring, there is a much greater risk of damaging the newly awakening grass crowns.) If a severe thatch problem is discovered in spring, you are faced with deciding if more damage will be done by dethatching in spring or by leaving the thatch on the lawn for the summer. When it is time to dethatch, mowing the lawn fairly low just before starting will make the job easier. If you are up to it, in small areas remove thatch by raking back and forth. Hand raking is a backbreaking way of removing thatch from any but the smallest areas. There are several better ways to accomplish this task. If the thatch isn't so severe that it is smothering the crowns of the grass plants (over an inch deep), consider using a core aerator to solve the problem. The cores of soil will pull up the microorganisms needed to digest excess thatch naturally, turning it into nutrients for the lawn. For a more serious thatch problem, there are mechanical dethatchers. These machines are usually rented for the day or many lawn care companies offer this service. The best type of machine for dethatching is a vertical mower. It has a row of blades that cut grooves into the thatch and pull it up. The other alternative is a power rake. This is like a lawn mower with spring tines attached to the blades. Power rakes work, but they don't pull up as much thatch and they pull up more grass than a vertical mower, sometimes damaging the lawn. If you are using a mechanical dethatcher, it is better to set it too high than it is to set it too low. Since you almost always have to go back over spots several times, the blades can be lowered when you become accustomed to working with the machine. Once the thatch is pulled up to the surface, it should be raked up and either composted or disposed of. Do not allow it to sit on the surface of the grass for very long. There are also liquid products that can be applied to the lawn to speed up the breakdown of thatch. They are not as reliable as mechanical dethatching and should only be considered to aid digestion on a healthy lawn, not to resolve a thatch buildup problem. All About Soil Compaction Plant roots need air in the soil and good drainage. In their absence, root systems will be shallow and weak. In lawns, signs of compacted soil include poor drainage (puddling), excessive weeds despite the use of good weed controls and poor grass growth despite good maintenance practices. When the soil is compacted, nutrients and water are slow to get to the roots, further weakening the plants. Soil compaction is a problem in high traffic areas or where heavy equipment has been used for construction, grading or even mowing. There are fancy pieces of equipment that can actually measure soil compaction, but that isn't really necessary for the homeowner. If you don't know if your soil is compacted, you can check it out yourself. Take a sharp shovel into the lawn and try to dig out a scoop of turf and the underlying soil. If it isn't a struggle to sink the shovel in at least half way, your soil isn't too compacted. Look at the sample you removed. There are probably lots of grass roots that extend 4-6 inches below the surface. You will be able to see spaces in the soil between the particles and it will crumble fairly easily. If you have to jump up and down on the shovel to get it into the soil, you have a problem! Look at the sample you removed. There probably won't be a deep, extensive root system for the grass. It will also look fairly solid and will be hard to break up. This soil needs aeration. All About Aerating Aeration is best done in late summer or early fall. Depending on your soil type and the traffic on your lawn, it may need aerating every two or three years. Despite all the claims about aerating your lawn by wearing spikes attached to your shoes, mechanical core or plug aerators are the only good way to aerate a lawn. They pull up a core of soil and leave it on the surface. This does the best job. Core aerators can be rented, or many lawn care companies offer this service. These machines should pull out plugs that are about the size of your little finger. It may sound like too many holes, but the aerator should be run back and forth until there are 20-40 holes in every square foot. The holes allow for air, rain and nutrients to penetrate the soil better. It also gives the roots room to grow. The lawn will look rough for a few weeks, but this is the right amount. Leave the cores on the surface to dissolve over the next few weeks. The soil in the cores contains millions of microorganisms that help digest thatch naturally, creating a healthier lawn. If we have a long dry period after core aerating, run the sprinkler to help break down the cores. Avoid using aerators that are simply rollers with spikes. They just push soil aside, adding to the compaction problem. The up side of core aerating is that it encourages deep rooting, increases air in the soil, improves water and nutrient penetration, helps break down thatch and encourages growth of beneficial soil microorganisms. The down side of core aeration is that it also brings up quite a few weed seeds from the soil bank. You may want to consider using a preemergent herbicide the following spring to minimize the weed problem. "Dethatching and Aerating Lawns". Bachmans. March 11, 2009 <http://www.bachmans.com/tipsheets/lawn/Dethatching.cfm>.  |
