Lawn Thatching and Thatch
 
Define Thatch:
Lawn thatch is the excessive build up of unwanted material in your lawn that can choke out air, water, and sunlight. Excessive build up of thatch in your lawn can cause grass to stop growing and even become more prone to insects and lawn diseases. Thatch is composed of dead grass build up, pine needles, or moss.  It can also refer to the dead layer of sod that is left over after an insect infestation.

When is the best time to thatch a lawn?

The best time to thatch the lawn with a thatching rake is in the spring and in the early fall. Lawn thatching allows your lawn to recover before it gets too hot or too cold. Most lawns will not look that bad after they get de-thatched. Because lawn thatchers take a lot of moss or bad grasses out of your lawn, the lawn may need to be re-seeded in order for it to heal properly.  (If there is a lot of moss you may also need to add iron to get rid of the remaining moss before seeding.) Lawns with 'dead thatch' can be very tricky to deal with if insect damage is extensive. (See 'dead thatch' below) Lawn thatching can be done using a lawn thatcher or a thatching rake. 
 
Why use a power rake? (Thatch lawn)

Power-raking or dethatching a lawn can remove harmful yard build-up. This can allow water, air and sunlight to reach the surface of the soil. Lawns can grow better once lawn thatch has been removed. This can be done with a machine or by using a thatch rake.


Benefits of Lawn Thatching

In order to maintain a healthy lawn and keep it looking its best it may be necessary to thatch your lawn on a yearly basis. To know whether or not your lawn needs to be thatched annually, you need to be able to recognize whether or not you have a
thatch problem. Below are some of the most obvious signs that a thatch problem exists in your lawn:

 1.   You have a lot of moss in your lawn. Moss is referred to as living thatch.  It causes problems for your lawn because it is ugly and because it can out grow cool season grasses. Often these thatch problems are fairly easy to fix. The best way to fix a thatch problem caused by moss is to thatch it out with a thatching machine. A thatching machine works great because the moss has virtually no roots.  Having a thick healthy lawn going into the Winter, will make it less likely to have a severe moss
infestation.

 2.  Another sign that you have a problem with thatch is if you have dead grasses building up in your lawn.  This relates directly to two factors.  The type of grass you have in your lawn, and varying amounts of sunlight available to your lawn throughout the year.  The way to treat this is to thatch the lawn and then reseed it with better grasses. Unfortunately, this may only be a short term fix and you may end up needing to tear out the whole lawn and replacing it anyway. 

3.   Another sign that you have a thatch problem is if you have pine needles building up around the edge of your lawn.  Not only do the pine needles choke out water and sunlight, but they are also acidic.   You may need to use lime when over seeding these areas to counteract the effects of the acidic pine needles.  

4.   How do I de-thatch a lawn or get rid of thatch?
There are four ways to manually thatch your lawn.  If it is a small lawn, you could do it by hand. De-thatching a one thousand square foot front yard could easily take one man two or three hours. It is really backbreaking work. Most people prefer to de-thatch or thatch a lawn by renting a machine. These machines are called lawn thatchers or power rakes.  Another way is to hire professional to do this for you. Rates vary according to area, but in Seattle we typically charged $100-1$20 for a two thousand square foot yard including clean up.  With two people this will take about an hour. If you are doing this by yourself, you should plan on three to four hours. Bigger lawns will of course take longer. Before thatching make sure to mow your lawn about 1/3 shorter than usual. If you normally cut your grass at 1.5",cut it down to 1".  It is best to thatch when the grass is dry. A wet lawn    can very quickly turn into a messy problem.

5.   If the main problem is moss, try using iron first to get rid of the moss or lawn thatch.  (Sweet soil is an alkali that may raise the PH to inhibit future growth, however it is not very effective once the moss is already there.)  It may be important to stay on top of it, by adding moss out to your lawn in the Spring and the Fall. In Seattle, the best time to put the iron on the lawn is when it is actively growing.

6.   How often do I need to thatch my lawn?
It depends on the lawn and the type of climate. Most experts recommend thatching once every 3-5 years. Some yards may not need to be thatched for many more years.  You can determine if you have thatch by placing your foot on the grass and seeing if your foot makes an impression that stays on the lawn.