Iris tenuissima is often found and photographed around the northern end of California's Great Central Valley. Below, it flourishes near Manzanita Lake, Lassen Volcanic National Forest in sunny openings in manzanita scrub, and partly shaded areas in nearby yellow pine, red fir and deciduous oak woodlands.
In Castle Crags State Park, on the west side of Shasta County, the Shasta iris is frequently seen along roadways and nearby openings in the pine-oak forest. Most plants grow as single individuals, though attractive clumps can develop in places where several generations of seeds fall in one spot.
Open areas in pine forests around Junction City, west of Weaverville in Trinity County often host Iris tenuissima. They flower most abundantly along road cuts or places where there had been a recent brushfire.