Slender phlox (Microsteris gracilis) is a very early spring wildflower native to Western North America from Canada to the Midwest. Slender phlox is also found in Mexico and parts of South America. This annual is variable in shape. Slender phlox can be branching and decumbent, almost tuftlike or erect and slender. Usually growing between 2 to 4 inches in height, it can be up to 20 inches tall.

The lance-shaped leaves, glandular and pubescent, are opposite except near the stem top where they are alternate. One or more tubular flowers encased in a calyx of sepals occur at the top of the stem. The five-petals of the flower are white to bright pink with a yellowish center. The fruit is an achene (single dry seed).

Slender phlox grows in open grassy spaces, woods, seeps and other moist places.

These specimens were growing along the Pacific Crest Trail near the Crystal Lake Fish Hatchery (Shasta County CA).