Iris hartwegii is part of the middle altitude yellow pine forest flora, in a band extending the length of the western Sierra Nevadas. It disappears at higher elevations where fir trees replace the pines, and in lower regions dominated by deciduous oaks. Though found sporadically throughout the pine forests, Sierra iris blooms in especially good numbers only in situations where direct sunlight reaches the forest floor. Sometimes you can find virtual carpets of iris blooming in old logging sites, road cuts, or areas of forest thinning or recent forest fires.