How do I know when there ready, Its almost sept. here in minnesota, and the trees have there seeds, but when do I collect?
I think that you pick them up off the ground when they are falling. Try giving the branch a little shake and see if they start spinning down. PS It's almost september everywhere john ;)
For best results, collect and sow maple seeds when fully developed but still soft and green rather than hard and brown.
For most Acer with seeds that mature in the fall, picking from the tree, while still in the condition that Ron B suggests, around mid-september usually works just fine.