The Crater Lake rockcress (Boechera horizontalis) is a candidate for listing as threatened or endangered by the state of Oregon. NPS Photo. Mt. Shasta Arnica (Arnica viscosa)grows between volcanic rocks on Wizard Island. NPS Photo. Crater Lake National Park contains several plants of conservation concern. These are plants that are rare, sensitive, or threatened in some manner. Plants are considered rare or sensitive when their distribution is limited due to having small population sizes across a large area, or having all of their populations concentrated in a small area. Plants that are threatened or endangered have legal protections to help keep their habitats intact. Even though all of Crater Lake National Park is protected, special management attention is focused on Crater Lake’s plants of conservation concern.