Downy Phlox is an erect native perennial forb growing from 6 inches to 24 inches high on unbranched (usually) stems that are covered with fine whitish hair.
The leaves are lance like, less than 1/2 inch wide, opposite, without stalks and have an abrupt sharp point; surfaces can have fine hair as can the leaf margin, which is without teeth.
The inflorescence is a panicle of loosely branched clusters of individually stalked flowers (cymes) atop the stem and from the upper leaf axils. Cluster stalks and flower stalks have fine hair.
The flowers have a green calyx with hairy lance shaped long-pointed lobes making the calyx longer than the corolla which forms a tube shape. The corolla tube forms 5 reddish-pink to pink lobes (white to lavender shades can exist) that spread laterally at the top of the tube to form 5 petals, which have narrowed bases and rounded tips that usually end in a blunt point; the entire flower is about 1/2 to 3/4 inch across and looking like a typical phlox flower. The lobes of the corolla are not notched but have deeper colored spots near their base. These spots are nectar guides for insects. The 5 stamens and the pistil do not protrude from the throat of the corolla tube.
Seed: Fertile flowers produce an ovoid 1/8 inch seed capsule which breaks into 3 sections dispensing black seeds explosively when mature and dry. Seeds require 60 days of cold stratification for germination. Plant in the fall and let winter do the work.
Habitat: Stems grow from a small taproot that has a fibrous root system, and stems are usually single, but multiple stems can occur as plants age. The plant grows in mesic to dry prairies and open woods and is occasionally found in open meadows. As a native species it is usually not afflicted with mildew as are many garden phlox species.
Names: The genus Phlox covers 67 species, mostly in North America. The word is from the Greek and means 'flame' which would have something to do with the colorful shape of the inflorescence atop a slim erect stem. The species, pilosa, refers to 'soft' or 'downy' and refers to the soft hair which cover most parts of the plant. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: Phlox flowers tend to look very similar so petal shape and leaves must be checked. Compare - Garden Phlox, P. paniculata; Wild Sweet William, P. maculata; and Wild Blue Phlox, P. divaricata.
Above: The long green hairy calyx with its five pointed lobes is longer than the corolla tube which also has fine hair. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: The inflorescence consists of many clusters atop an unbranched stem.
Below: 1st photo - The 3-section seed capsule that will split open when dry and explosively discharge the seeds. 2nd photo - A small grouping of plants.
Below: 1st photo - Note the fine hair on the stem, leaf veins and leaf edges. 2nd photo - The root system of Downy Phlox.
Below: Flower color can vary between many shades of pink depending on soil and amount of sun.
Notes: Downy Phlox is indigenous to the Garden area. In addition, Eloise Butler planted it in 1907, '08, '09, and '18. Martha Crone planted it in 1945. Cary George planted some in 1993. It is a plant of the Tall Grass Prairie. In North America the plant is native from the Dakotas south to Texas and then east to the coast. In Canada it is reported in Alberta and Ontario. Within Minnesota it is found in most counties except in a northern tier above and east of a diagonal line running from Carlton NW to Kittson, i.e. those not in a deciduous forest area. In Illinois, Maryland, New Jersey, New York and Pennsylvania it is listed as "endangered".
Minnesota Species: According to USDA there are 9 accepted subspecies of this plant. Both the U of M Herbarium and the Minnesota DNR list the Minnesota native subspecies as var. fulgida (Wherry) Wherry. [Note: USDA uses the title 'subspecies' and then lists the 'variety' under the subspecies, although in 8 of the 9 subspecies there is only the one variety, whereas MN authorities have dispensed with the subspecies label.] The only other two native species of Phlox in Minnesota are Wild Blue Phlox, P. divaricata and Wild Sweet William, P. maculata.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"