We can learn Dhamma from nature, from trees for example. A tree is born due to causes and it grows following the course of nature. Right here the tree is teaching us Dhamma, but we don't understand this. In due course, it grows and grows until it buds, flowers and fruit appear. All we see is the appearance of the flowers and fruit; we're unable to bring this within and contemplate it. Thus we don't know that the tree is teaching us Dhamma. The fruit appears and we merely eat it without investigating: sweet, sour or salty, it's the nature of the fruit. And this is Dhamma, the teaching of the fruit. Following on, the leaves grow old. They wither, die and then fall from the tree. All we see is that the leaves have fallen down. We step on them, we sweep them up, that's all. We don't investigate thoroughly, so we don't know that nature is teaching us. Later on the new leaves sprout, and we merely see that, without taking it further. We don't bring these things into our minds to contemplate. —Ajahn Chah "Tree Dhamma"