How to Plant and Grow Phlox

Phlox is one of those dependable summer flowers any large sunny flowerbed or border shouldn't be without. There are several different kinds of phlox. Garden and meadow phlox produce large panicles of fragrant flowers in a wide assortment of colors. They also add height, heft, and charm to a border. Low-growing wild Sweet William, moss pinks, and creeping phlox are effective as ground covers.

Where to Plant Phlox

 Because there are so many types of phlox, there is no single best planting site. Tall garden phlox should be planted in full sun, whereas woodland phlox needs partial shade to thrive. But what all phlox has in common is that the soil should be fertile and evenly moist, with excellent drainage that is slightly acid, neutral, or alkaline. 

The design options for phlox are as numerous as the phlox types, from the front or back of the border to a rock garden or woodland. Phlox can be planted as specimens but especially the low-growing types are particularly striking as drifts.

How and When to Plant Phlox

You can plant phlox either in the spring after there is no more danger of frost, or in the fall, at least one month before the first fall frost to give the roots time to get established. 

Dig a hole at least twice the size of the nursery container and deep enough so that the top of the root ball is level with the soil surface. Backfill the hole and gently tamp down the soil around the base. Water immediately.

Spacing depends on the type of phlox because the width or spread of the mature plant varies greatly. Plant tall garden phlox about 18 inches apart and leave about 2 feet between creeping phlox types.

Phlox Care Tips

Light

The light requirements for phlox differ so you need to make sure you match the variety of phlox to the light conditions of your intended planting site, or vice versa. Tall garden phlox needs full sun to thrive. Woodland phlox, on the other hand, should be in partial shade—light conditions that mimic its native habitat as an understory plant.

Soil and Water

 The soil should be moist and rich, with excellent drainage. Poorly draining soil is problematic and should be avoided. In terms of pH, phlox is undemanding; it grows in a pH range between 5.0 and 8.0.

Water the plant until it is fully established and shows vigorous new growth. After that, phlox has moderate watering needs. Ideally, it should receive 1 inch of water per week but most types tolerate short dry spells. Mulching around the base of the plant helps to retain soil moisture.

Temperature and Humidity

Phlox is winter-hardy down to zone 3 but it does not do well in a hot climate or extreme humidity.

Fertilizer

If planted in rich, fertile soil, phlox does not require any fertilizer other than a one-time application of a balanced granular fertilizer in the spring after the plant has come out of dormancy. For the amount to use, follow product label directions.

Pruning

 Phlox needs more cleanup than pruning, which ensures that plant diseases such as powdery mildew are not perpetuated. In the fall, after the first killing frost, cut the stems back to a height of 2 inches. In the spring, remove all dead foliage from the plants. This also makes room for new growth.

Potting and Repotting Phlox 

For container plants, choose a short variety such as creeping phlox. Plant it in a container with large drainage holes and fill it with well-draining potting mix. Potted phlox looks best when it fills the container so plant more than one and leave at least 6 inches between plants. Keep in mind that unlike phlox planted in garden soil, potted phlox needs frequent watering and also repeated fertilization, as the nutrients wash out.

When the roots have filled the pot or grow out of the drainage holes, repot the plant in a container that is 2 inches larger in diameter. Fill it up with fresh potting soil.

Pests and Problems 

As a native plant, phlox has few serious problems. The most common one is powdery mildew, which is unsightly but not deadly. It can be prevented by providing good air circulation between plants and removing infected foliage to contain the spread. There are also phlox varieties bred for powdery mildew resistance.

How to Propagate Phlox

Phlox often reseeds itself freely. If you want the small volunteer plants elsewhere, dig them up and replant them in another spot. They will undergo a transplant shock but if you keep them well-watered, they will recover after about a week.

Otherwise, you can also propagate phlox from stem cuttings. In the late spring, take a 4-inch cutting of a healthy stem and remove the lower leaves. Dip the cut end in rooting hormone powder and insert it about halfway in a 4-inch pot filled with damp potting mix. Place the pot in a location with bright light but away from direct sunlight and keep it moist but not soggy. It will take at least a month for roots to develop. Wait until the cutting has grown a bunch of new leaves before transplanting it in garden soil.

Types of Phlox

'Blue Paradise' Phlox

Phlox paniculata 'Blue Paradise' offers purple-blue flowers that appear to change color throughout the day. It grows 3 feet tall and 2 feet wide. Zones 4-8

Creeping Phlox

Phlox subulata is a low-mounding plant smothered with bright flowers in spring. Its slender 1/2-inch leaves are evergreen, stiff and prickly. It seldom tops 6 inches tall. Zones 3-8

'David' Phlox

Phlox paniculata 'David' is a disease-resistant selection with fragrant, pure-white flowers that grows 4 feet tall. Zones 4-8

'Franz Schubert' Phlox

Phlox paniculata 'Franz Schubert' bears big flowerheads of lilac-pink blooms in summer and early fall. It grows 3 feet tall. Zones 4-8

'Laura' Phlox

Phlox paniculata 'Laura' grows about 3 feet tall with mildew-resistant leaves and large dense panicles of fragrant purple flowers accented with a white eye. It is very long blooming from midsummer to fall when it attracts hummingbirds and butterflies. Zones 4-8

'Miss Lingard' Meadow Phlox

Phlox maculata 'Miss Lingard' bears strongly fragrant pure-white flowers in early summer. It grows 3 feet tall and 18 inches wide. Zones 5-8

'Natural Feelings' Phlox

Phlox paniculata 'Natural Feelings' displays unique, thready lavender-pink flowers from midsummer to fall. It grows 28 inches tall and 20 inches wide. Zones 4-8

'Orange Perfection' Phlox

Phlox paniculata 'Orange Perfection' shows off coral-pink flowers from summer to fall. It grows 32 inches tall and 14 inches wide. Zones 4-8

'Peppermint Twist' Phlox

Phlox paniculata 'Peppermint Twist' is a groundbreaking selection with pink flowers striped with white. It grows 16 inches tall and 14 inches wide. Zones 4-8

'Sherbet Cocktail' Phlox

Phlox paniculata 'Sherbet Cocktail' offers unique purple flowers tipped in chartreuse. It offers good disease resistance and flowers from midsummer to fall. It grows 28 inches tall and 20 inches wide. Zones 4-8

'Volcano Purple' Phlox

Phlox paniculata 'Volcano Purple' is a compact, disease-resistant selection with rich purple flowers. It grows 26 inches tall and 24 inches wide.

Woodland Phlox

Phlox divaricata is a shade-loving wildflower with fragrant, lavender-purple flowers in spring. It grows 1 foot tall. Zones 4-8

Phlox Companion Plants

Candytuft

Sparkling white candytuft, with its cool evergreen foliage, brightens any rock garden or wall for several weeks in spring. At bloom time, plants are covered with umbels of pure white flowers that fade to pink. Compact selections are now available. Where happy, this plant will spread. Supply good drainage, and cut back spent flowers to keep plants neat.

Baby's Breath

With its loose, billowy panicles of tiny single or double pink or white flowers, baby's breath provides a lightness and airiness to flower gardens. The creeping forms drape beautifully over rock walls. After bloom time, shear the plants to deadhead and for neatness. Plants prefer sweet (alkaline) soils with full sun and excellent drainage.

Shasta Daisy

Easy, always fresh, and always eye-catching, Shasta daisy is a longtime favorite. All cultivars produce white daisy flowers in various degrees of doubleness and size. The sturdy stems and long vase life make the flowers unbeatable for cutting. Shasta daisy thrives in well-drained, not overly rich soil. Taller sorts may need staking.

Blazing Star

Valued for its unusual flower shape, blazing star sends up erect spires of usually magenta, sometimes white flowers. Emerging from grasslike foliage, the blooms make a dramatic statement in flower gardens with other perennials, annuals, or even shrubs. Well-drained but moisture-retentive soil is a must for this prairie native.