Five major native plant communities exist in the park:
- Deciduous riparian forest
- Pinyon-juniper woodland
- Mixed mountain shrubland
- Sagebrush shrubland
Deciduous riparian forest covers more than half of the park, where boxelder, green ash, river birch and narrowleaf cottonwood are dominant species. Pinyon-juniper woodlands consist primarily of Rocky Mountain juniper, pinyon pine, mountain mahogany, Mormon-tea, blackbrush, mountain sagebrush, serviceberry and skunkbrush. Mixed mountain shrubland occurs as a transitional zone between the deciduous riparian forest and the pinyon-juniper woodland. Gambel oak is the dominant overstory tree in the shrubland.
Diverse wetland, riparian and aquatic plant communities have become established on seeps, in small ponds and along the river. The lush plant growth at the base of the falls gives the area a tropical feeling during the summer months. Sandbar willow is usually the dominant riparian shrub. Reed canary grass, broad-leaved cattail and woolly sedge are the dominant emergent vegetation. The hanging garden sullivantia, a plant known only from wet canyon walls of western Colorado, is present in at least one hanging garden at Rifle Falls.