Wild Blue Phlox is a delicate perennial phantom of the semi-open woods; the mostly erect stems can be from 1 to 1-1/2 feet high, unbranched and finely hairy. Some stems are infertile, some fertile. As the stems are somewhat weak, the plant may tend to lean on others.
Leaves: Each flowering stem has only a few opposite lance shaped leaves that have fine hair, smooth margins with fine hair and are stalkless, clasping to the stem with flat bases. Stems that do not flower have leaves that are smaller, somewhat more ovate, with more rounded tips.
Inflorescence: The inflorescence is a loosely branched cluster (a cyme) at the top of the stem. These clusters have glandular hair.
Flowers: The flowers range from light blue to purple, are about 1 inch across with the 5 flattened (spreading) lobes joined at their bases to form a tube as long as the flower lobes are wide. The lobes are not notched and are widest near the tips. The 5 stamens and pistil are inside the tube and do not protrude. The outer calyx of the flower is a dark green, linear in shape with 5 long pointed lobes (teeth), densely hairy.
Fruit: The mature flowers form an ovoid seed capsule containing several small brown seeds; the capsule, when mature and dry, breaks into 3 sections dispensing the seeds explosively. Seeds require 60 days of cold stratification for germination.
Habitat: Wild Blue Phlox grows from a fine rhizomatous root system in moist woods, partial shade to shade, best with dappled sun, wet-mesic to dry-mesic moisture conditions. They die back by mid-summer after setting seed. Infertile shoots will remain green longer.
Names: The genus Phlox covers 67 species, mostly in North America. The word is from the Greek phlox and means 'flame' which referred to a Greek plant that had a flame colored inflorescence atop a slim erect stem. The species name, divaricata, is Latin, meaning "spreading" or "growing in a straggling manner". The author name for the plant classification - 'L.', is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Above: 1st photo - The inflorescence is a loose cluster of flowers atop the slim stem. 2nd photo - The petals of the 5-parted flowers are widest near the tip with bases that form a tube containing the stamens and pistil. 3rd photo - Stem leaves are stalkless and hairy, just like the stem.
Below: The flower cluster as shown far below, can be quite large. Note the glandular hair on the flower stalks, flower calyx, and cluster stems. The corolla tube extends beyond the calyx teeth as far as the the petals are wide.
Notes: Wild Blue Phlox is not indigenous to the Garden area. Eloise Butler obtained plants for the Garden numerous times, first in 1907 from the Government Reservation (Ft. Snelling area), again in 1908 and 1911 from a source in Minnetonka MN; on April 11, 1912 and April 18, 1913 from Groveland Park, Minneapolis. On Oct. 12, 22 and 24, 1914 she planted 500 of the species that she obtained from the grounds of the Catholic Seminary in St. Paul. On Oct. 26, 1916 she planted 51 sourced from Groveland Park in St. Paul MN and more from Minnehaha Park in 1917 and 1920. [Only in those days could you obtain plants in that manner.] Wild Blue Phlox was listed on Martha Crone's 1951 inventory of plants in the Garden at that time. Gardener Cary George added plantings in 1987 and Susan Wilkins in 2005. Plants are found in the Woodland Garden and in the Fern Grove of the Upland Garden. It is native to most counties in the southern half of Minnesota except the far SW. Not known north of Morrison and Pine counties. In North America it is found from the central plains eastward in the U.S. and in Canada it is found in Ontario and Quebec.
Minnesota Species: There are two subspecies of P. divaricata. The accepted full species name considered native to Minnesota is Phlox divaricata (L.) subsp. laphamii (A.W. Wood) Wherry. Both the U of M Herbarium and the MN DNR list it as such. The other is subsp. divaricata which is native in North America only eastward of the Mississippi Valley. The only other two native species of Phlox in Minnesota are Wild Sweet William, P. maculata and Downy (or Prairie) Phlox, P. pilosa.
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"