I've read that you get a clover when there is a rainbow in town! From the moment I've read that piece of info I haven't had a rainbow though, so I still can't test if thats true.
I had read this too. I had two clovers on the ground and just tried pulling them with a rainbow in the background. Nothing. I don't know if it has to be a double rainbow? That is my next test. But a single rainbow did NOT work.