Is there a method to dethatch zoysia best without harming the runners? I went over a small portion of my lawn yesterday with a thatch rake, and came up with a ton of thatch, but felt like I was catching in the zoysia quite a bit. I tried to exercise care and back off when I felt it catching, but it still felt like it was doing some harm. Is this just a natural effect of detatching, or was I going at it too aggressively?
You do have to dethatch a zoysia lawn whenever the thatch buildup gets too thick, and because of the growth habit of zoysia, the vertical mower or rake will naturally pull up stolons. Try not to dethatch more often than you have to. When you are done dethatching, you can mow off the ends that stick up, if they bother you. The lawn will quickly regrow any areas where the ground was exposed. You can minimize damage by trying not to dig in much, but some pulling up of runners is inevitable. This is normal and will self correct pretty fast. Lawns do benefit from a small amount of thatch, to maintain soil moisture, and build the organic matter content in the soil.
Do not dethatch near the end of the growing season, or your lawn will not have time to recover. Also, fertilizing generously before and after dethatching will help the plants regrow and fill in.
There are also environmentally healthy products that inoculate thatch with microbial digesters, which break down the thatch into soil-building humus. Applying a nitrogen fertilizer at the same time will help. Example product: earth smart thatch digester (estd)
Here are some resources for further reading: