Thatch is the mat of fibre between the grass and soil on your green. Although some thatch (5-6mm) is desirable too much can have a devastating affect on the playing surface.
When thatch builds up beyond the optimum level it can quickly cause problems with surface drainage, which in turn can encourage fungal diseases like fusarium patch and this can kill off huge areas of turf if left unchecked. Recovery from such attacks can also be troublesome and expensive.
This tendency to encourage disease is related to thatch’s ability to soak up and hold large quantities of water. Indeed if you squeeze a sample of thatchy turf you will usually see water appearing as if you were squeezing a wet sponge.
Conversely in summer, thatch can cause the opposite problem, when it dries out completely it becomes hydrophobic and will not re-wet. When this happens, no amount of irrigation or summer rain will make the thatch take in water, and the much needed liquid is simply shed off the surface of the green leaving the soil below parched and grass plants struggling to survive.
To deal with severe thatch, we might suggest a regime of aeration including scarification, hollow-tining and top-dressing.
It is important to get the thatch layer reduced as quickly as possible and this usually means that the major work is left until autumn when the disruption to play is minimised.
Other recommendations might include application of wetting agents in summer to help the soil to re-wet properly, but this must be done alongside a surface breaking operation like sarrell rolling or pencil tining