If you take a botany class, you learn that the leaves or stems of certain plants have aromatic compounds. My mother had a Florida anise, Illicium parvifollium, in our yard and she would always crush a leaf when we walked outside and let us inhale that wonderful licorice fragrance. Another tree whose leaves have a distinctive but not so pleasant smell is our deciduous black cherry, Prunus serotina. The stems and leaves and fruit pits of this native tree is filled with cyanide related compounds and if you break the stem and sniff you get a nose full of that bitter almond essence. Interesting, deer can eat the fresh leaves to their hearts content, but the toxic compounds become accessible when the leaves wilt and broken limbs which have fallen into horse or cattle pastures have caused animal deaths.