There are several native plant communities that occur at the Ridgway State Park including the following (in order of prevalence):
- Pinyon-Juniper Woodland
- Sagebrush Shrubland
- Riparian Forest and Shrubland
- Mixed Mountain Shrubland
- Ponderosa Pine Woodland
- Western Slope Grasslands
- Saline Bottomland Shrubland
The Pinyon-Juniper Woodland is the principal forest type found in the park. Pinyon pine, Utah juniper and a rich understory of shrubs and grasses comprise this plant community, which occupies dry slopes and hills throughout the park. The second most common plant community in the park is the Riparian Forest found along the park’s riverways that is composed of Narrow-leafed cottonwood, Gambel oak, Coyote willow, Water birch as well as many shrubs and grasses. The least prevalent forest is the Ponderosa Pine Forest, which occurs in drainages along the west side of the reservoir and in Pa-Co-Chu-Puk and is dominated by Ponderosa pine, Rocky Mountain juniper, Gambel oak and the occasional Colorado Blue spruce.
The most prevalent of the shrubland plant communities in the park is the Sagebrush Shrubland found on open dry areas throughout the park. The dominant species are Big sagebrush, rabbitbrush and Indian ricegrass. The Mixed Mountain Shrubland community is diverse, including mountain mahogany, Gambel oak, serviceberry, Squaw-apple, Big sagebrush and Skunkbrush sumac. This shrubland occupies the drier slopes and provides understory for the pinyon-juniper community. Alkaline flats along Alkali Creek support a Saline Bottomland Shrubland, which includes Four-wing saltbush, rabbitbrush, Alkali sacaton, squirreltail and Western wheatgrass.
As for other plant communities found in the park, Western Slope Grasslands are in the open areas and consist of the sod-forming grasses of Blue grama, Galleta and Western wheatgrass, as well as the bunchgrasses, Needle-and-thread grass and junegrass. Wetlands with cattails, water sedge and horsetails exist around the reservoir and in the Uncompahgre River Valley, above the reservoir and below the dam.