Artist Tim Knowles has created a series called, "Tree Drawings", in which he connects pens and brushes to the branches of trees, allowing their natural sway in movement in the wind to create the design.
The results are amazing, and quite surprising. Check them out:
"A series of drawings produced using drawing implements attached to the tips of tree branches, the wind’s effects on the tree, recorded on paper. Like signatures each drawing reveals the different qualities and characteristics of each tree."
Reminds me a bit of the bicycle drawing machine.
Tree Drawings [Tim Knowles]