My son in Christchurch has thistles scattered over his lawn. What's the best way to get rid of it?
Gardening in Christchurch NZ
I don't know what type of thistles are troubling your son, but I'm going to guess that thistles are pretty much the same the world over. These articles should explain pretty well how to deal with them. https://www.gardeningknowhow.com/plant-problems/weeds/canada-thistle-control.htm