On 17 May, 17:51, wrote:
Does a chemical exist that one could spray on grass to
slow down its growth.... yet not kill it?

And can a consumer buy it?

The chemical used is normally Maleic Hydrazide. It can sometimes turn
finer grasses (Bents and fescues) brown, but this dose disappear after
a while.
You can stunt the growth for up to 6 weeks at a time. (Do a test patch
on your lawn first.
Regards
Data