Monday, March 17, 2014

Lawn Care 101: Aeration vs. Dethatching

If your lawn doesn’t seem to be greening up as you would expect, even when you fertilize, you may have other problems. If no disease or insect activity is prevalent, you should check the thatch layer and see if this is excessive (over ¾” to 1” thick). Excessive thatch is a common problem with thick, full-sun established lawns that are fertilized regularly. 

Thatch refers to the living and dead layer of organic material (grass clippings, dead sheaths, excessive surface tillers and rhizomes) which, if allowed to become too thick, can prevent proper aeration, water penetration and fertilizer uptake. 

Dethatching the lawn means utilizing a mechanical dethatcher that literally combs or rakes through the lawn just above the soil line with a reel of metal tines that pull the thatch out of the lawn. If this needs to be done, a remarkable amount of thatch can be brought up from the base of the lawn, sometimes as much as a two to three inch layer of material, which then needs to be raked or vacuumed up and removed. Dethatching has an excellent aeration value and “opens up” the lawn for excellent water and fertilizer penetration. As with all renovative procedures on a lawn, power dethatching should be completed when the lawn has good rejuvenative, recovery capability. In other words, my favorite months to do this are April, May and September. In many cases, I recommend an immediate fertilization and possibly overseeding. This is an excellent procedure to recommend if it needs to be done.       The fees for this are priced out on our lawn renovation pricing schedules. 

Aeration is a process in which the soil underneath the lawn is penetrated, either by a hollow tine that pulls out a soil plug varying in size from 3/8” to 3/4” and varying in depth from 2 ½” to 6” in the case of deep tine aeration. Aeration is sometimes accomplished with a vertical knife machine. This procedure is recommended in lawns which are typically grown in sunny conditions (not in all cases) that are suffering from over-compaction. This over-compaction might be caused by poor subsoil or it might be caused by excessive wear, such as in the case of an athletic field or golf course. In these more intensively used turf environments, it is not unusual to core aerate four or five times per year. Sometimes a light sand topdress follows the core aeration. This procedure is stimulative to the grass population as it allows air, water and nutrients to penetrate directly to the root zone. This can be thought of as a pruning of the roots. Just like pruning a hedge, the roots can rapidly regenerate – especially when the aeration (as we recommend) occurs during seasonal periods with the faster recovery. This is typically April, May and September. Following the aeration with fertilization and, as indicated above, a light topdress can also be recommended. It is always necessary to prepare the client for the appearance of the aeration. It is desirable and typical to leave the cores on top of the lawn. In many cases, we use a chain link drag to break these cores up which provides a nominal topdress of soil material on the lawn surface. Using a turf core puller to take three or four samples from the lawn and examining the subsoil can indicate the necessity of recommending core aeration. Indicators are poor root penetration toward the subsoil as well as a very dense compacted soil.

Joe Schmid
David J. Frank Landscape Contracting, Inc.

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