The length of wildflower season as well as the abundance of wildflowers is dependant on winter snowfall and spring rain. On very wet years some flowers persist even into September. Some of the most common wildflowers in Fossil Butte National Monument include blue flax (Linum lewisii), leafy bluebell (Mertensia oblongifolia), sego lily (Calochortus nuttallii), Hood's phlox (Phlox hoodii), Wyoming paintbrush (Castillejalinariifolia),mule's ear (Wyethiaamplexicaulis) and sticky geranium (Geraniumviscosissimum).
