Phlox Care

Phlox is a genus of 67 species of perennial and annual plants in the family Polemoniaceae. They are found mostly in North America in diverse habitats from alpine tundra to open woodland and prairie. Some flower in spring, others in summer and fall.

Low growing phlox is a great ground cover, growing in mounds 4-6 inches thick.

Medium height varieties, great for mass plantings, rarely grow taller than 2 feet high.

Tall phlox, great for a backdrop or border, grow in clumps reaching between 3-5 feet high.

We offer all sizes of this plant. The star shaped blooms come in pale blue, red, white, pink, or purple. Hardy in USDA zones 2-9, this plant likes full sun to partial shade.


Planting Phlox

The best time to plant Phlox is in early spring, after the threat of frost has passed. Choose a sunny location with moist well-draining soil. Good air circulation is important, so space plants 18-24 inches apart. Dig a hole twice the size of the pot’s diameter. Place the plant in the hole with the top of the root ball even with the soil. Fill in the hole and water it thoroughly. Mulch around the root zone to keep roots cool and moist.

Watering Phlox

Newly planted Phlox definitely will need weekly watering until established. During a normal growing season, unless you have rainfall, an inch of water per week is recommended. During the heat of the summer, foliage can wilt easily, which is a sign that more moisture is needed. When watering it is best to keep the foliage as dry as possible. Water in the morning at the root zone, avoiding the leaves. A 2-3 inch layer of mulch will help the soil to hold moisture.


Fertilizing Phlox

When first planted, it is a good idea to fertilize your Phlox. To promote growth and vigorous blooms, fertilize your Phlox annually in the late winter or early spring. Use a general purpose slow-release fertilizer for flowering plants and follow the instructions on the packaging. You will want to fertilize this plant again in late summer just before it goes dormant. Water well after each application.

Pruning Phlox

Phlox plants normally do not require pruning. If you desire a bushier plant with more flower heads, cut back the stems by one half in the early summer. In addition, if you would like to shape your plant, you can trim it back after blooming. It is perfectly fine to let the plant grow naturally and skip pruning all together. Deadheading spent flowers can encourage a second bloom or prevent unwanted reseeding.


Caring For Phlox in Pots

Plant your Phlox in a good quality potting mix, adding fertilizer if the mix does not contain any. This fast growing plant will fill a container quickly, so choose one that is large with drainage holes. Space multiple plants 6 inches apart to allow for spread. Water your Phlox regularly, allowing the soil to completely dry in between. Place the pot in a sunny location and apply a general purpose fertilizer every 7-14 days. You can cut the plant after blooming to shape the plant and encourage a second bloom.


Winter Care for Phlox

Phlox is a perennial plant that will return year after year. Hardy in USDA zones 2-9, this plant will need some protection to survive the winter. After the first frost, cut the stems back to the soil line. Before the ground freezes, apply a 2 inch layer of mulch on top of the plants. This will protect the roots from a damaging freeze thaw cycle and preserve moisture in the ground. When the risk of frozen temperatures is over, remove the mulch and uncover the plants.

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Common Phlox Care Questions

Does Phlox Like Sun Or Shade?

Phlox can do well in either full sun or partial shade, however, the more sun the more flowers they will produce. 

Does Tall Garden Phlox Spread?

Most phlox will spread and dividing them every few years, early in the spring before new growth is evident, is a good idea to help with sufficient air circulation. If you're transplanting, be sure to give them about 18 inches of room to grow into.

Are Phlox Invasive?

Tall garden phlox varieties are non-invasive but there is a similar-looking plant, Dame’s rocket (Hesperis matronalis) from Eurasia that is very invasive. Dame's rocket has 4-petaled flowers instead of 5 and belongs to the Mustard family (Brassicaceae), not the phlox family.

What Is The Growth Rate For Phlox?

Phlox is a fast-growing plant and if planted in a container, will quickly fill the empty space so be sure to choose a planter large enough to accommodate the expected mature size. 

Phlox Leaves Turning Yellow And Brown?

Yellow leaves on phlox are likely caused by too much water. Heavy moisture causes waterlogged roots, a lack of oxygen and also blocks the plant from absorbing nutrients. If this continues, root rot ensues and the leaves will eventually fall to the ground. Yellow leaves which eventually brown can be indicative of a fungal infection in phlox, powdery mildew

Phlox Annual Or Perennial?

There are varieties of phlox that are perennials and some that are annuals.

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Author Chris Link - Published 07-08-2021