Garden Phlox (Phlox paniculata): July’s Native Plant

Phlox paniculata, also known as Garden Phlox or Tall Phlox, is an herbaceous perennial native to the eastern and central United States. This plant is in the Polemoniaceae family and is hardy to USDA zones 4-8. P. paniculata is a clump-forming perennial that grows 2-5 feet tall, with elliptical, opposite, 3-6 inch dark green leaves. They do best in full sun to part shade and moist well-drained soils. Garden phlox blooms in panicles of 5 petaled flowers that come in a variety of colors including; pink, blue, lavender, burgundy, and white. 

At Wellfield, we tip the phlox with pruners in late May to early June. Tipping entails taking roughly one-third of the height off the top, pruning back to a node. This does a few things. It promotes a shorter plant that is less likely to flop over and need staking. It can delay and prolong the bloom time, and if there are large clusters of phlox, you can get them to bloom in succession, by tipping the plants toward the front and leaving the plants toward the back alone. You will get blooms on the plants toward the back first and before they start to fade, the tipped phlox in front will start blooming and continue later into summer. Tipping phlox also promotes lateral growth to branch out from the cut, producing an increased number of blooms. Garden phlox can suffer from powdery mildew, which can be helped by thinning out a few stems and proper spacing to aid in better air flow, as well as avoiding top watering the plant. This plant can also be cut down to the ground in fall to help prevent powdery mildew the following season and to keep a tidier look.

P. paniculata has outstanding ornamental value in the garden as a straight native species and its many cultivated varieties. This can be a great border plant to line paths, planted in large swaths, or it can be used as a backdrop to lower growing perennials and shrubs.

Phlox paniculata ‘Ultraviolet’ starting to bloom in our English Cottage Garden

If you’re looking to attract pollinators to the garden, Garden phlox is a great choice. P. paniculata attracts a variety of bees, flies, moths, butterflies and occasionally hummingbirds. While Garden phlox is a food source for many, it is generally deer and rabbit resistant.

Phlox paniculata is often confused with Hesperis matronalis or dame’s rocket. Flowers of both plants can be alike in color, bloom clusters, and bloom time can also be similar. A few ways to tell these two apart are the opposite, untoothed leaves and five petaled flowers of phlox, compared to the alternate, toothed leaves and four petaled flowers of dame’s rocket. Dame’s rocket also tends to bloom a little earlier in the season than phlox. Dame’s rocket is on the Indiana Department of Natural Resources list of terrestrial invasive plants.

Hesperis matronalis, or dame’s rocket, in bloom

Phlox paniculata is a beautiful perennial that can brighten up any garden. This plant is fairly easy to grow and requires fairly little maintenance once established. P. paniculata has a long bloom time and comes in a variety of colors. Planting P. paniculata will attract several pollinators to the garden. We have quite a few varieties planted at Wellfield, many of which are beginning to bloom now. Head out to the Gardens to see this eye-catching native plant of the month!

Kyle Strain

Manager of Public Horticulture

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