Naida sent this link where there is a good article, from “Michigan State University Extension News Gardening in Michigan”, on the Monarch research:
https://www.canr.msu.edu/news/monarch-butterfly-research-update-may-2019
Monarch Butterfly Research Update
May 20, 2019 by Linda Welch
Monroe County Master Gardener Association 
great article and oddly enough, this is something I have already been doing— different reasoning but none the less……so I am happy that it has been beneficial for the Monarch.