Ecologically, the park uplands are dominated by montane grassland and short-grass prairie species, including Arizona fescue, Parry oatgrass, blue grama, needle-and-thread grass, western wheatgrass, Junegrass and squirreltail. 
Common wildflowers and shrubs include Indian paintbrush, scrub oak, golden aster, gilia, copper mallow, wallflower, sulfur-flower, wild rose, locoweed, fringed sagewort, rabbitbrush and snakeweed. A sparse montane coniferous forest grows on the flanks of slopes and ridges, where both ponderosa and limber pine are present with an understory of mountain mahogany, rabbitbrush, currant and Spanish bayonet.
In moist canyons, Douglas fir becomes the dominant tree, mixing with Colorado blue spruce, ponderosa and limber pines. Stands of aspen grow in shallow soils over bedrock and around rock outcrops along the lower slopes of canyons and drainages, along with shrubby cinquefoil, common juniper, thimbleberry, waxflower, valerian, yarrow and pussytoes.
Diverse wetlands, riparian and aquatic plant communities have become established around the reservoir in seeps, tributary drainages and below the dam. Found here are pale blue-eyed grass and few-flowered ragwort, both considered to be rare plant species.
View the Eleven Mile & Spinney Mountain Plant list for more information.
