My Fellow Turfgrass Combatants,

Good job.  Carry on with your great work in the service of your lawn.  In this block of instruction, I will discuss THATCH.  That's right; you heard me.  THATCH.  Thatch buildup results because you are not following orders.  So, it is your fault.  Thatch can be a good thing - but like many good things; too much is NOT good.

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

Write this down: You will never have more than 0.5 inches of thatch.  Now repeat after me; "I will never have more than 0.5 inches of thatch in my yard."  AGAIN!  I CAN'T HEAR YOU!  Okay.  If you have more than that, its time to get out of your Class B uniform and get to work.

How do I "de-thatch" or remove thatch from a lawn?

There are four ways to manually get rid of thatch from your lawn.  If it is a small lawn, you could do it by hand.  De-thatching a 1,000 square foot front yard could easily take 2 to 3 hours.  It can be real back breaking work - or, awesome PT - depending on how you look at it.  Most people prefer to do de-thatching or thatch removal by renting a machine (Like I do - I also have a thatching rake I can pull behind my tractor).  These machines are called a lawn thatcher or "power rake".  These lawn thatchers should cost between $65 and $120 for a 4 hour rental.  Another way to do it is to hire someone to do it for you.  Rates vary according to area.  They typically charge about $150 to $200 for a 2,000 square foot yard, including clean up.  Clean up can be a big deal.  Depending on how much thatch you have, you could have several large trash bags or a couple pick-up trucks full of dead grass.  With two people this takes about an hour.  If you are doing it by yourself, you should plan on 3 to 4 hours.  Bigger lawns will take longer.  Before thatching, make sure to mow your lawn about 1/3 shorter than usual.  If you normally cut your grass at 3", cut it down to 2".  It is best to thatch when the grass is dry.  A wet lawn can very quickly turn into a mess.

If the main problem is moss, try using iron sulfate first to get rid of the moss.  (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 iron to your lawn in the spring and the fall.  The best time to put the iron on is whenever moss is actively growing.

When is the best time to thatch a lawn? (“Power Rake”)

The best time to “de-thatch” a lawn with a thatching tool or machine is in the spring or in the early fall.  That falls in line with the doctrine I have been spouting off to you - don't mess with your lawn in the middle of the summer or the middle of the winter.  Lawn thatching in the spring or fall allows your lawn to recover before it gets too hot or too cold.  De-thatch before you core aerate.  Most lawns will not look that bad after they get de-thatched.  Depending on how much thatch and other organic material the machine pulls up (sticks, stones, debris), your lawn could look like western Iraq.  Because lawn thatchers can 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 sulfate 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. 

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 to 5 years.  Some yards may not need to be thatched for many more years.  You can tell if you have thatch by placing your foot on the grass and seeing if your foot makes an impression that stays on the lawn, not unlike the drought diagnosis I mentioned in my section on irrigation.  You may also be interested in finding out more about dethatchers or power rakes...the different types of weapons for this sort of operation.