Photo by: Photomara / Shutterstock.

A summer garden mainstay since colonial times, garden phlox owes its enduring popularity to its heady clouds of billowy blooms, no-fuss nature, and slender stature. But the real icing on the cake is the long flowering season, with the first blooms opening in July and often lingering through September. “Phlox carries the garden through the dog days of summer, holding down the fort until the asters and blazing stars come on board,” says plant specialist James Locklear, author of Phlox: A Natural History and Gardener's Guide.

Garden phlox is also one of those rare perennials that you’ll find in nearly every hue on the color wheel, even hard-to-find shades of blue. In fact, the choice of colors and cultivars is so vast, it can be daunting to choose among them. Here’s a look at some of our top picks, along with advice for incorporating phlox into your own garden.

On this page: Phlox Basics | Grow Your Own | Care Tips | Pictures

PHLOX BASICS

Botanical name:

Phlox paniculata

Common names:

Garden phlox, summer phlox, tall phlox, border phlox

History and origin:

Phlox are native to many parts of the eastern and central United States. They were exported to Europe in the early 18th century, and many of the early cultivars originated in England and Germany. Several cultivars that are still grown in gardens today were developed in the 1930s by German plant breeder Karl Foerster, who once declared that "a garden without phlox is not only a sheer mistake but a sin against summer."

Zones:

4-8

Height:

1 to 5 feet, depending on the cultivar.

Characteristics:

The dainty five-petaled flowers of garden phlox (from the Greek word for “flame”) are packed by the dozens into dense clusters, or panicles, ranging in size from 4 to 6 inches tall and 6 to 8 inches wide. The flowers are often sweetly fragrant, and some cultivars are adorned with central eyes in contrasting colors. While most phlox have green leaves, some have variegated foliage with creamy white or yellow margins.

Bloom time:

Although the typical bloom period for garden phlox is July through September, you can extend the flowering season by choosing cultivars that have been bred to bloom a bit earlier or later than the norm. Often phlox are categorized as early season, late midseason, and late season bloomers. By planting varieties of each, you’ll have phlox in full flower all summer long and well into autumn.

Cultivars:

There are well over a hundred cultivars of garden phlox, resulting in a great diversity in plant height, panicle sizes, and flower color. The Dutch have been the most ambitious breeders in recent years, says Locklear, aiming at bigger flowers, exotic colorations, and much shorter plants that can be used at the front of the border or in containers. In the U.S., many of the newest cultivars have been singled out for their improved resistance to powdery mildew and other foliar diseases. Heirloom cultivars with smaller flowers are also making a comeback because they are reminiscent of those grown in Victorian-era cottage gardens.

Pros:

  • Long-lived, often lasting in the garden for decades under hospitable growing conditions.
  • Provides color in the heat of the summer, when many other perennials begin to fade.
  • Attracts bees, butterflies, and hummingbirds.
  • Rarely needs staking.

Cons:

  • Susceptible to damage caused by powdery mildew.
  • May be grazed on by deer and rabbits.
  • Although phlox are easy to start from seed and often self-sow, the offspring of most cultivars do not remain true to the color of the parent plant.

GROW YOUR OWN

Light requirements:

Although phlox flowers best when given full sun, it is actually a native woodland plant and doesn’t mind a bit of shade, especially when grown in hot southern climates. As a general rule, aim for about 6 hours of sun exposure daily.

Soil:

Grow in moist, fertile, well-drained soil enriched with compost or other organic matter. Phlox prefers soil that’s slightly alkaline and will benefit from regular applications of lime if your soil tends to be acidic (see Garden Soil 101).

How to plant:

If you are growing bare-root or potted plants, put them in the ground in spring after the danger of frost is past, spacing plants about 18 to 24 inches apart to ensure good air circulation. Thoroughly water, and then apply a layer of mulch around the root zone to help keep the roots cool and moist. You can also grow phlox from seeds, but they must be started indoors in late winter (see Starting Seeds under Fluorescent Lights).

Propagating:

The easiest way to clone your garden phlox is by division. Simply dig up the plants in early spring or late summer and separate the clumps into sections with a sharp knife and replant immediately. Each division should contain at least 3 or 4 shoots and a portion of the root system. It’s also possible to propagate phlox from stem cuttings taken in early summer.

Photo by: Pelevina Ksinia / Shutterstock.

Using in the garden:

Few perennials can perk up the languishing midsummer landscape like garden phlox. Use them in mass plantings, cottage gardens, meadow gardens, pollinator patches, cut flower gardens and containers, or wherever where you need to add a punch of color. Because garden phlox is available in a wide range of heights, you can find varieties perfect for the front of the border, back of the border, and anywhere in between.

Plant and seed sources:

One of the most extensive online sources for phlox, including heirloom varieties dating back to the early 1900s, is Perennial Pleasures Nursery in Vermont. Grower and manager Rachel Kane specializes in garden phlox (her favorite perennial) and grows 142 cultivars, offering more than 80 varieties for mail order.

Other online purveyors of phlox plants and seeds include:

CARE TIPS

Watering:

Phlox doesn’t like drought and should be watered during dry spells or whenever you see the foliage begin to wilt. Ideally, phlox should receive about an inch of water per week during the growing season. To keep the foliage healthy, water at the root zone rather than overhead.

Dividing:

To prevent overcrowding and improve the vigor of your plants, divide them every 3 to 4 years. Telltale signs that phlox is ready for division include sparser blooming and centers that begin to weaken or die out.

Pruning and deadheading:

Phlox doesn’t normally require pruning, but if you want to delay blooming and get bushier plants with more flower heads, pinch or cut back the stems by one-third to one-half in early summer. Deadheading the spent flowers may also extend the bloom period and prevent unwanted reseeding.

Mildew prevention:

The No. 1 enemy of garden phlox is powdery mildew, a fungus that attacks the plant’s leaves and causes them to become shriveled and gray. The malady is particularly prevalent in humid climates during the hot, muggy days of summer. Plants growing in partial shade are also more susceptible. The best preventive measure is to improve air circulation by selective thinning of the plant stems and providing adequate spacing. The problem can also be avoided by planting mildew-resistant cultivars, such as all the varieties featured here. When thinning plants, remove all but four to five strong stems in early spring.

Winter care:

After the first killing frost, cut back the stems just above above the soil line and remove and discard the foliage, especially if your plants have been affected by powdery mildew. In colder regions, protect the roots by applying a layer of mulch before the ground freezes.

PICTURES

Swipe to view slides

Photo by: Volcko Mar / Shutterstock.

P. paniculata ‘David’

Bearing large heads of pure white flowers, ‘David’ floats like billowy clouds among the other perennials in the summer garden, providing cooling contrast to the heat of brightly colored flowers. A good choice for growing in hot, humid climates where other phlox can struggle, becasue it is one of the most mil­dew-resistant varieties. Also try ‘Delta Snow’, another white-flowered cultivar with contrasting lavender eyes

Height: 3 to 4 feet

Bloom time: Late summer to early fall

Photo courtesy of Walters Gardens, Inc.

P. paniculata ‘Bright Eyes’

Combining two cheerful shades of pink into one delightful bloom, ‘Bright Eyes’ will enchant you with its rosy-pink centers that peep out from a halo of soft pink petals. The huge dome-shaped flower heads are up to 9 inches long, held atop strong stems that remain upright without staking. Also try ‘Eva Cullum’, another two-toned charmer with medium-pink flowers and deep-pink eyes.

Height: 18 to 24 inches

Bloom time: Midsummer to early fall

Photo by: Andrew Pustiakin / Shutterstock.

P. paniculata ‘Blue Paradise’

Almost like a floral mood ring, the blossoms of ‘Blue Paradise’ seem to shift color throughout the day, depending on light exposure. They appear medium purple under bright daylight, but take on violet-blue tones at dusk and dawn or during cloudy days. Paler centers and tiny red eyes add to the allure. Also try ‘Ending Blue’, another color-shifting phlox with blooms that appear to be lilac-pink in bright daylight and soft purple-violet during the evening hours.

Height: 2 to 3 feet

Bloom time: Late summer to fall

Photo by: Andrew Pustiakin / Shutterstock.

P. paniculata 'Peppermint Twist'

You’ll feel like a kid in a candy store when you first lay eyes on 'Peppermint Twist' and its equally enticing counterpart, ‘Twister’. Both look like peppermint pinwheels, with the first bearing medium-pink flower petals with contrasting white stripes and the latter showing off white petals and bold magenta stripes. Use either one of these delightful dwarf cultivars to add whimsy to a container planting or the front of the border.

Height: 12 to 18 inches

Bloom time: Midsummer to early fall

Photo by: Garden World Images / Alamy Stock Photo.

P. paniculata ‘Shortwood’

‘Short­wood’ is a chance seedling that inherited the best traits from both of its parents — the strong mildew resistance of ‘David’ and the colorful pink blossoms of 'Eva Cullum'. It is the only variety to garner a top five-star rating in a multiyear evaluation of more than 70 phlox cultivars conducted by the Chicago Botanic Garden. It was lauded not only for its prolific rosy-pink blooms, which covered the plant from mid-July to early October, but also for its superior immunity to powdery mildew and spider mites. Also try 'Blushing Shortwood', which has pale lilac flowers accented by strokes of white.

Height: 3 to 4 feet

Bloom time: Midsummer to fall

Photo courtesy of Walters Gardens, Inc.

P. paniculata ‘Red Riding Hood’

Bright cherry-red flowers with a hint of carmine infuse the fading midsummer garden with a strong punch of color. A compact, bushy growth habit makes this a good selection for the middle of the border and vase cuttings. We also love ‘Red Super’, which has mesmerizing fuchsia flowers with dark red centers.

Height: 24 to 30 inches

Bloom time: Midsummer to early fall

Photo courtesy of Walters Gardens, Inc.

P. paniculata Flame® Series

Barely over a foot tall, this new series of dwarf cultivars from The Netherlands is ideal for containers, courtyards, small urban gardens, and even as an edging plant at the front of the border. A wide array of flower colors is available, including two new captivating options: Flame White Eye (white with star-shaped fuchsia eyes) and Flame Blue (deep blue buds opening to pale lavender-blue petals). Despite their diminutive stature, all members of the series feature large, fragrant blooms.

Height: 15 to 18 inches

Bloom time: Midsummer to early fall

Photo by: Lana B / Shutterstock.

P. paniculata ‘Orange Perfection’

This dazzling garden phlox takes you on a spin to the warm sector of the color wheel, producing giant 5 to 6 inch clusters of vivid salmon-orange flowers accented with bright fuchsia eyes. The color will bleach somewhat in strong sun, so grow this phlox in a spot that receives some afternoon shade for the best color intensity. Looks stunning when planted with black-eyed Susans and salvia.

Height: 32 to 40 inches

Bloom time: Midsummer to early fall

Photo by: Del Boy / Shutterstock.

P. paniculata Natural Feelings Series

A garden phlox without petals? That almost unthinkable incongruity is the real asset of the Feelings® series of phlox from Holland, which was bred to replace the petals with narrow bract-like florets, resulting in plumes of color that remain lush and full from late July well into September. The flowers are also remarkably long-lasting when used in bouquets. Natural Feelings features vivid mauve-pink florets accented with delicate brush strokes of bright green. Other showy varieties in the series include Red Feelings with ruby red bracts and Fancy Feelings with star-shaped deep pink bracts.

Height: 2 to 3 feet

Bloom time: Midsummer to early fall

Photo by: Sharon Dickson / Millette Photomedia.

P. paniculata ‘Shockwave’

Named for its shocking yellow and green variegated foliage, this compact cultivar will brighten up the perennial garden or a container planting even when it’s not in bloom. In sum­mer, the vivid yellow margins lighten to creamy yellow and dense clusters of lavender-pink flowers with white starburst centers emerge, creating a striking contrast.

Height: 12 to 18 inches

Bloom time: Mid to late summer

Photo by: Dency Kane / Millette Photomedia.

P. paniculata ‘Norah Leigh’

Here is another phlox appreciated just as much for the foliage as the flowers. The boldly variegated leaves are creamy white with narrow brush strokes of green, a color combination that beautifully complements the white flowers and bright pink eyes. Also try ‘Crème de Menthe’, which pairs green and white variegated foliage with pearly pink flowers accented by pale-plum eyes.

Height: 2 to 3 feet

Bloom time: Midsummer to early fall

Photo by: Susan Marie Sullivan / Shutterstock.

P. paniculata ‘Robert Poore’

Named after a noted Mississippi landscape architect, this heat-loving cultivar thrives in sultry southern climates, where it has proven to be one of the most mildew-resistant varieties. The showy heads of magenta flowers, which sit atop sturdy 5-foot stems, command attention even when planted at the back of the border. A good companion plant with the equally heat tolerant P. paniculata ‘David’.

Height: 4 to 5 feet

Bloom time: Mid to late summer

Photo by: Rock Giguère / Millette Photomedia.

P. paniculata ‘Sherbet Cocktail’

Another cultivar bred in The Netherlands, this phlox is notable for being the first to include yellow in its floral color palette, starting with almost pure yellow buds that open to reveal soft pink petals and creamy yellow edges. The large clusters of densely packed florets are held atop strong, compact stems.

Height: 2 to 3 feet

Bloom time: Mid to late summer

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