Thatch

In my post about aeration I mentioned thatch a few times, so I thought I should share my two cents' worth on that subject.

Some people confuse thatch with dead grass blades.  Thatch is the dead compacted organic material that accumulates above the soil but below the base of the grass plants.  If you can see it without digging, it's not thatch.  When we start aerating I'll try to post a picture of a plug so you can see the thatch layer.  

Thatch is good, in the proper balance.  A layer of thatch 1/2" thick keeps roots cooler and cushions the grass plant.  Bacteria break it down into nutrients that are re-used.

Too much, though, causes problems.  Water can't reach the roots as well, and runs off or evaporates instead.  Too-thick thatch harbors insects and disease, and since water can't penetrate well, neither can fertilizer or pest controls.

But power raking or de-thatching is not a good answer.  Power raking removes huge amounts of organic material but destroys the grass crown ( the part of the plant where roots and leaves emerge).  It really trashes the lawn, opening the turf to weeds, and it can take an entire summer or more for the grass to recover.

So the problem isn't thatch, then, but thatch that doesn't decompose.  Fertilizing properly adds nutrients that help with bacterial action to break it down, but too much fertilizing makes thatch worse.  Aeration does wonders (see Aeration).  When we're asked to de-thatch a lawn, we always suggest an aeration instead.  Unless, that is, someone wants to re-seed the area.  But that's another topic.