Curl-leaf Mountain Mahogany - Cercocarpus ledifolius

 

Curl-leaf Mountain Mahogany (Cercocarpus ledifolius) is a small tree or shrub in the Rose Family (Rosaceae). It has dense wood and waxy green leaves. 

Generally the plant looks like the photo below, mainly green with grey stems. The trees can live for over a thousand years in some places.

 

However, in the spring, small yellow flowers emerge.

The flowers eventually develop into seeds that are nicknamed hellfeathers, because if they spiral down inside your shirt, you might be saying a few expletives. 

For more info on Curl-leaf mountain mahogany, see this Wikipedia page.