Eucalypt leaves, dry, spent, given back to the earth. Hard, resistant, they take longer than any other leaf to break down. They make better mulch than compast for that reason. I really love the smell Eucalypt, fresh or dry, but the best is when the end of summer is near and the summer storms come and the rain brings out such a wonderful feast of smells, an olfactory orgasm if you like. Petrichor (the word for) the smell of rain on dry soil and leaves, atmospheric aromatherapy, wonderful stuff. Never despise a dry leaf, food for the senses.