Geranium cuneatum, subspecies hololeucum
Geranium cuneatum, subspecies hololeucum, or Hinahina as it's commonly known, is one of four subspecies found in Hawaii, and is native to the Hawaiian Islands. In Hawaiian "hinahina" means silver (Silversword plants are known as ʻĀhinahina). If you check the undersides of the leaves, especially on a plant that's away from the road and not coated in dust, you'll note the silvery pubescence from which the name comes. Hinahina are the only woody geraniums in the world.
Before the eradication of many of the feral sheep and goats on the mountain, there were very few of the hinahina around as they are eagerly browsed by the feral ungulates. It's one of the upper vegetation margin plants that has really come back strong since the removal of most of the sheep and goats.