Perennial Phlox

Phlox paniculata

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Photo of perennial or summer phlox flower cluster.
Perennial phlox has big, showy clusters of flowers. A tall, late-blooming native wildflower of woodland borders, steamsides, and gravel bars, it is also an old-fashioned garden favorite.
Other Common Name
Summer Phlox; Garden Phlox
Family

Polemoniaceae (phloxes)

Description

Perennial phlox is a tall, late-blooming perennial phlox with big, showy, fragrant clusters of flowers. The flowers are in dense, pyramidal, terminal clusters in many shades of purple, red-purple, rose, and rarely white. Cultivated forms come in many different colors and color patterns. The individual flowers have the typical phlox shape, with a narrow tube that flares out with 5 flat petal lobes. Blooms July–October. Leaves opposite, sessile (stalkless), oblong to lance-shaped, prominently veined, and spaced apart on stems.

There are many horticultural cultivars in a great variety of colors that are found at garden centers and in home landscaping. This phlox is an old-fashioned favorite, and some of the cultivated varieties can be found growing untended at old homesites.

Size

Height: 2–4 feet.

perennial_summer_phlox_side_9-2-15.jpg

Photo of perennial or summer phlox flower cluster, seen from side.
Perennial Phlox (Summer Phlox; Garden Phlox)
Many “natural” occurrences of perennial phlox might actually be remnant populations of garden plants.

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Photo of perennial phlox cultivated variety
Perennial Phlox (Cultivated Variety)
There are many cultivars (varieties bred for specific traits) of perennial phlox. This cultivar has dark purple centers and more compact flower heads than the natural form.
Habitat and conservation

Occurs in moist soils in borders of woods, streamsides, below bluffs, and along gravel bars. Because it has been a favorite garden plant for so many years, and many cultivars have been developed, many “natural” occurrences of this plant might actually be remnant populations of garden plants. Look around for old foundations, cisterns, and other cultivated perennials and trees to see if you’re at an old homesite.

image of Perennial Phlox Summer Phlox Garden Phlox distribution map
Distribution in Missouri

Cultivated statewide; occurs naturally generally south of Missouri River and in east-central counties.

Human connections

An old-fashioned garden favorite that your grandmother might have grown, perennial phlox bears big, colorful clusters of flowers starting in midsummer and continuing to bloom for a long time. Most people use it as a perennial border flower.

Another bonus for the gardener is that hummingbirds are attracted to the flowers.

Some cultivars have problems with powdery mildew on the leaves, phlox bugs, and root rot, but native strains are more hardy. Check into disease resistance before purchasing.

Ecosystem connections

A variety of butterflies, skippers, and moths, including the hummingbird-like sphinx moths, visit the flowers. Perennial phlox is especially attractive to the cloudless sulphur, a large, clear-yellow butterfly that migrates southeast in late summer and fall.

This phlox is also a late-summer nectar source for hummingbirds as they are gaining strength for their fall migration south.

Herbivorous mammals and insects chew the foliage.

Several types of insects also eat the leaves or suck the sap.