How to Grow and Care for Phlox

Phlox is a common garden plant that comes in many forms, with nearly 70 species of perennial and annual varieties, from creeping to tall, with flowers that bloom from mid spring through late summer. The three main types grown in gardens are creeping phlox, woodland phlox, and tall phlox. Colors range from white to shades of pink, purple, and blue. Most phlox will bloom in partial shade conditions. The taller varieties make excellent cut flowers and are attractive to pollinators. It is a favorite choice for cottage gardens.

Phlox Care

Different types of phlox require slightly different care, but all phlox have some basic care elements in common.

• Plant phlox in well-draining, rich, slightly acidic soil.
• Plant phlox in an area with partial to full sunlight.
• Give phlox space between other plants to promote air circulation to prevent mildew, and water them at the roots, not from above.
• Top dress them with compost in the fall (they shouldn't need any other feritlization).

Light

Most phlox bloom well in partial sunlight but will also tolerate full sunlight. Woodland phlox will bloom in partial to full shade.

Soil

Phlox need well-drained soil that is rich with compost. The soil should be neutral to slightly acidic.

Water

It's best to water phlox at the base, instead of from above, to help prevent mildew forming on the leaves. Phlox are somewhat drought tolerant but need regular watering during their blooming season.

Temperature and Humidity

Tall phlox may wilt a bit on a hot summer day. Give them cool water at the base if the flowers or stems droop. Humidity can be an issue for phlox because of a tendency for powdery mildew to form on the leaves. This mildew is harmless to the plant but is somewhat unsightly, causing a pale gray bloom to appear on the leaves. The best way to prevent powdery mildew on phlox is to make sure the plants have adequate air circulation, so be sure they have space. If they start to get crowded they can be easily divided.

Fertilizer

Generally phlox don't need any fertilizer, but if your soil is thin you should add some amendments. Tall and woodland phlox also benefit from a bit of top dressing with compost or composted manure in the fall.

Types of Phlox

There are numerous varieties and cultivars of phlox and a few different types, but the most commonly grown in gardens are creeping phlox, woodland phlox, and tall phlox. There are also annual phlox available in many nurseries.

Moss Phlox (Phlox sublata)

Also known as creeping phlox (not to be confused with Phlox stolonifera) or moss pinks, Phlox sublata forms a mat of spiky leaves covered in flowers in mid spring. The plants are low growing, reaching at most 6 inches in height. Moss phlox come in a wide variety of colors, from white to soft blue to hot pink, and work very well in rock gardens and along paths.

Creeping Phlox (Phlox stolonifera)

It can be easy to confuse this variety with Phlox sublata, but there is one important difference: moss phlox likes full sun, while creeping phlox does fine in partial shade. The most well-known cultivars are 'Blue Ridge' (small pale blue-purple flowers) and 'Sherwood Purple' (larger pale purple flowers).

Woodland Phlox (Phlox divaricata)

Woodland phlox (Phlox divaricata), aka wild blue phlox, are shade-loving flowers that are among the first perennials to bloom in spring. The roots form a strong mat and the stems grow about 12 to 14 inches tall with star-shaped flowers of white or periwinkle blue. 'Blue Moon' is a common cultivar with pale blue flowers; 'Chattahoochee' is a new hybrid with pale blue flowers with a showy magenta center.

Annual Phlox (Phlox dummondii)

Phlox dummondii are small colorful annuals with hues as vivid as perennial phlox. They're great to use in container plantings, and with a bit of deadheading will bloom continuously all summer.

Wild Phlox (Phlox maculata)

Wild phlox, also known as meadow phlox or wild sweet William, grow freely in meadows near woodlands and shady roadsides. They come in a range of pale pinks and purples, grow about 2 feet tall, and provide lovely delicate color in the spring countryside.

Tall Phlox (Phlox paniculata)

Tall phlox, also called garden phlox, form cone-shaped clusters (panicles) of flowers in a rainbow of colors from white to pastel pink to deep blues, purples, and magentas, some with colorful eyes. They grow between two to four feet tall depending on variety, with some new dwarf hybrids. Well-loved cultivars include 'David', 'Eva Callum', 'Blue Paradise', and 'Bright Eyes'.

Pruning Phlox

Phlox don't really need pruning so much as they need deadheading. Snip the tops of the plants once blooms are spent, this will encourage more blooms. Once the flowering season is over, cut phlox back as desired, and they will regrow in spring.

Propagating Phlox

Phlox are very easy to propagate from divisions. As long as there is a bit of root attached, phlox cuttings also propagate readily. Apart from moss phlox, phlox tend to grow hardy root systems that can be pulled apart or cut into pieces. Divide the roots in the fall and replant as desired in your garden. They should flower in the spring but if not, they will catch up the following year.

With moss phlox, you need to find the rooted sections beneath the mat of spiky leaves. Cut away any dead or dried leaves. Replant the root section with some leaves attached.

Overwintering Phlox

Being very cold hardy, phlox don't need any special overwintering care. They do benefit from a top dressing of compost or manure in fall, and you may also put a light layer of natural mulch around them to protect the roots from extreme cold.

Common Pests and Diseases

Phlox have two main issues: hungry wildlife, and powdery mildew. Rabbits and deer love to nibble phlox. They like the flowers of woodland phlox, and then they'll eat the young leaves of tall phlox, which can delay the buds from forming. Using a natural repellent spray made for deer or rabbits should deter them.

Powdery mildew on the leaves can be prevented by leaving room between plants so the phlox can get adequate air circulation. Watering at the base of the plant and not from overhead can also help prevent mildew.

Phlox may also be bothered by spider mites, especially in warm, unusually dry weather. The leaves may turn yellow and curl downward. These can be removed by spraying your hose on the undersides of leaves to dislodge the mites and their young.

How to Get Phlox to Bloom

Phlox are prolific bloomers in the garden. But there may be various reasons why they don't bloom as vigorously as they should. Be sure to give adequate sun exposure to the varieties that like sun (tall phlox and moss phlox especially, which need six hours of sunlight). Powdery mildew can weaken the plant and this may affect the bloom output. Trim any mildewy leaves or cut those stems out to help keep the plant healthy. Dividing phlox plants that have become large or overgrown will also help to ensure healthy bud and flower production. You can divide plants in early spring or in the fall.

Deadheading, Trimming and Pinching

Moss phlox can get a bit leggy which can affect the formation of flower buds; be sure to keep the plants trimmed. The best time to shear them is after the first flowering in spring; sometimes moss phlox will give a second gentle round of flowering in late summer. You can also deadhead the spent flowers to keep the plants neat and make room for more blooms.

Some gardeners swear by cutting tall phlox back by about a third in early summer, to encourage more branching and more flowers. You can also pinch back the pairs of leaves at the top (like you would with mums) through the first week of July to encourage fluffier panicles of flowers.

Blooming Months

Woodland phlox start blooming in late April to early May and bloom for few weeks. Moss phlox start blooming usually in May. They have shorter bloom times than tall phlox, which usually start flowering in late June to July. To extend the summer bloom period, plant varieties of tall phlox that bloom across the season: some start flowering in late June, some not until August. The 'Early Start' cultivars begin blooming in early June. 'Franz Schubert' is a pretty pale lilac heirloom that blooms from late summer to early fall.