Shasta knotweed (Polygonum shastense), closeup of small branch showing rough, scaly twigs, folded leaves, and 5-petaled white flowers.  At 10,380ft along trail between Saddlebag and Steelhead Lakes in 20-Lakes Basin, Hoover Wilderness, Sierra Nevada mountains, California USA.
<a href="//commons.wikimedia.org/wiki/User:Dcrjsr" title="User:Dcrjsr">Dcrjsr</a>
CC BY 3.0
<span class="int-own-work" lang="en">Own work</span>