Lesson learned here was that pounding on the sidewalk makes holes in your fabric!
Moving to pounding on the deck and trying some yellow colored leaves from a silver maple also gave satisfying results. This tree started turning before the red maple and the leaves did take more pounding before they released color.
Adding in a leaf from a Japanese maple looked rather uninteresting during pounding but once the fabric was unfolded the look was better than anticipated.
On this last sample a red leaf from an oak tree was still hanging on the branch and although it seemed that nothing other than the veins of the leaf would show, once opened the result was very satisfying.
Still to be determined, will the color stay in the fabric after heat setting with an iron and washing? Of course, many art quilts will never be washed so an application where washing isn’t important is also a possibility. Stay tuned…