Timing for thinning out milkweed
What week in august can i remove abundant milkweed without destroying butterfly reproduction . In southeastern Michigan ( ann arbor)?
Washtenaw County Michigan
From egg to Monarch adult takes about 30 days. If you see eggs or larvae, you will know about how long to wait.
However, Monarch produce late into the season, and not all survive because of cold temperatures and killing frosts, while others develop “just in time” and fly south:
So, I would wait until your area has had a couple hard frosts before pruning milkweed, if you are conserving the butterflies.
For next season, consider this study of pruning in June in order to generate fresh growth and attract monarchs- https://www.canr.msu.edu/news/regrow-milkweed-for-monarchs-a-citizen-science-study