Controlling Lawn Thatch  

Thatch is a layer of undecomposed stems and roots that accumulates near the soil surface.  Grass clippings do not  contribute to thatch accumulation.  The rate at which thatch accumulates is determined by the type and vigor of   the grass in the lawn.  A thatch-prone bluegrass sod, that  is given lots of water and fertilizer, forms thatch more  rapidly than other grasses given less care.  

Thatch is a normal part of any lawn and only becomes harmful when the thatch layer is thicker than 1/2 inch.  When thatch becomes excessive, the lawn may root into the thatch rather than the soil.  Thatch does not hold  
moisture so lawns rooted into thatch will not tolerate dry  weather or cold temperatures.  In fact, a very thatchy lawn can be rolled up just like a rug when it dies out.  

Thatch management can take several forms.  

The easiest management technique is available to homeowners with underground sprinklers.  A 20 minute watering at mid-day, every day, helps control thatch by keeping it wet.  Such a watering also is adequate for  
watering the lawn.  

Three other options are open to homeowners without underground sprinklers.  They are power rakes, coring and topdressing.  Power rakes, or dethatchers, use power driven tines to tear the thatch out of the lawn.  Much of the lawn gets  torn out in the process.  While this is the most common  
way to dethatch, it is probably the least desirable. Sections of very thatchy lawns may need to be reseeded due dethatching injury.  Early September is the best time to use this type of thatch removal.  

A more desirable alternative is coring.  The limitation here is the availability of the coring machines.  Coring machines remove cores of soil and sod.  The hole allows air and moisture to penetrate the thatch  and help in its  
decomposition.  

A thin layer of soil can be applied over the lawn to  help decompose the thatch layer.  This topdressing may also be combined with coring.  The soil introduces  micro-  organisms that help decay the thatch. 

POWER RAKING (DETHATCHING) 

A VERY MESSY AND LABOR INTENSIVE JOB. PRIOR TO PERFORMING THE ACTUAL DETHATCHING OPERATION, MOW THE YARD AND BAG 
THE CLIPPINGS AT LEAST TWICE.  THEN POWER RAKE. AFTER POWER RAKING, THE YARD WILL  NEED TO BE VACUUMED TO REMOVE THE OFFENDING RESIDUE. WHEN FINISHED, UP TO 75% OF THE VEGETATION WILL BE REMOVED.  THIS CAN ONLY BE PERFORMED AFTER THREAT OF FROST  IN EARLY SPRING OR DONE IN EARLY FALLTO PREVENT PERMANENT DAMAGE TO LAWNS. THE AVERAGE 7,000sq ft SIZE YARD CAN PRODUCE OVER 1500LBS OF RESIDUE.