Garden or Summer Phlox in the wild version has whitish to magenta-pink flowers. The white flowers however, especially in a dense flower head, are usually a sign of a cultivated variety that when found has either been planted or has escaped from cultivation. The plant grows from 2 to 4 feet high on erect stems that usually have many branches near the top forming the inflorescence.
Leaves of the Garden Phlox are opposite, oblong to lance shaped, widest at the middle and have prominent lateral veins that do not reach the leaf margin but curl upward - an identifying characteristic. Leaves are usually more than 1/2 inch wide whereas native phlox species are less than 1/2 inch wide. They either have very short stalks or are sessile; they have smooth surfaces but some fine hair on the margins which are without teeth.
The inflorescence in cultivated varieties is a dense rounded cluster of showy flowers atop the stem (a panicle). In the more wild versions, the panicle is more broad and open.
The flowers are stalked, have a green calyx with 5 lance-shaped pointed lobes that are 1/2 as long as the corolla tube. The calyx may or may not have fine hair or glandular hair. The corolla of the flower has 5 lobes that join to form a long narrow tube. The upper end of the lobes spread laterally into 5 distinct lobes with a rounded but slightly angled tip. The 5 stamens with yellow anthers and the style do not protrude beyond the throat of the corolla tube. The style has a 3-lobed stigma.
Seed: Fertile flowers produce an ovoid seed capsule which has the 5 pointed lobes of the calyx persisting. When mature this capsule splits into 3 sections and discharges the dry seeds.
Habitat: Garden Phlox grows from a taproot with a fibrous root system and grows best in loamy soils with moist to moderate moisture conditions in full sun. During flowering times the plant, if a garden variety, needs good moisture. Clumps can form from the root. Garden Phlox is susceptible to powdery mildew.
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, paniculata, means 'with panicles' and refers to the inflorescence structure of this 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 these native species - Downy (or Prairie) Phlox, P. pilosa; Wild Sweet William, P. maculata; and Wild Blue Phlox, P. divaricata.
Above: The inflorescence forms a branched panicle with some additional branches from the upper leaf axils. 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: 1st photo - The calyx with its 5 thin lobes is 1/2 as long as the corolla tube. 2nd photo - Stamens are tucked inside the tube with the 3-lobed stigma of the style at the throat of the corolla tube.
Below: Comparison of the larger lower stem leaves (top leaf) with the mid to upper stem leaves (bottom leaf). Both are stalkless, smooth surfaced with prominent lateral veins.
Below: The leaf underside is paler in color, prominently shows the lateral veins and shows fine hair on the leaf margin.
Below: The characteristics of cultivated Garden Phlox are a rounded flower panicle. The plants at Eloise Butler are white.
Below: Cultivated Garden Phlox in the Upland Garden.
Notes: The first specific mention of Garden Phlox in the Garden is in Eloise Butler's log for Oct. 15, 1914 when she notes planting one near 'the others' so this is not the first appearance. On 26 Sept. 1917 she brought in 3 plants from Groveland Park in St. Paul. The existing white flowered plants in the Upland Garden probably arrived by avian seed delivery or by a planting by Martha Crone that she did not note in her log. Garden Phlox is native to certain states in the Eastern United States from Pennsylvania to Florida, west as far as Illinois and Louisiana. In Minnesota it, particularly the white flower version, is considered by both the U of M Herbarium and the MN DNR to be an introduced plant that has escaped from Garden cultivation or has purposely been planted. The three native species of Phlox found in Minnesota are noted above in 'comparisons'.
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"