Q: When should I aerate my zoysia lawn?
A: The right time to aerate zoysia, Bermuda and centipede lawns is in early summer, after they have greened up but before the heat stresses them too much. A further question, though, is whether you need to aerate at all.
Remember that ^aeration^ is the process of poking multitudes of holes in the ground in order to loosen it and in order for oxygen and water to penetrate better. If your soil is hard, aerating each year will help your lawn thrive. Another reason to aerate is to fight thatch. When a lawn is not mowed very often, grass stems that fall to the ground do not decompose very fast. After years of lackadaisical mowing, the layer of dead stems builds up so thickly that your grass roots grow in ^it^ rather into the soil. Since thatch dries out so quickly, your grass suffers from wide swings in available moisture. The constant stress can kill parts of your lawn.
Aerating with a rented “core aerator” pulls up thousands of plugs of soil which are left on top of the lawn. This soil sifts into the thatch layer and inoculates it with fungi which eat the thatch. Thatch control plus soil softening far outweigh the expense of renting an aerator machine.