Maple tree seedlings started to grow last weekend and are now spreading heavily through lawns. There is no need to worry about these because they will all die when you mow the lawn. It might take one or 2 mowings because the trees have to be tall enough for you to cut off the leaf. If the seedlings are too short the mower will pass right over them. If you want to live in a jungle you can save the trees and try to mow around all of them. If your children have cabin fever send them outside to dig up and transplant the trees (it will occupy them for days!)
Why are there so many this year?
I do not yet know the science behind it, but last fall we had a bumper crop of helicopters. I have a gutter helmet on my roof and I still had to get up there and blow the helicopters off. The helicopters are the seedlings that you see growing in the lawn.