I've managed to get rid of some by sending my sims to burn them several days in a row. After about the fourth time, my sim or a random townie will throw away some ashes. It can take up to 8 tries to burn all the leaves to ashes, then another four trips to get rid of the ashes. But yes it would be nice to have a fix so I'm not interrupting my plans or keeping sims up until they're ready to drop walking around their neighborhood to get all the leaves. It takes so long that I only bother with the ones near where my sims live.