Katmai's diverse plant communities include:
Sitka spruce, western hemlock, shore pine, lodgepole pine, black cottonwood.
Devil's club, salmonberry, blueberry, crowberry, red elderberry.
Fireweed, lupine, bluebells, forget-me-nots, glacier lilies.
Bluejoint grass, reedgrass, sedge, rush, cotton grass.
Sphagnum moss, feather moss, wolf lichen, reindeer lichen, crustose lichen.
This rich vegetation supports the park's famous brown bears, salmon runs, and diverse wildlife.