Learn About Phlox

How to Sow

Phlox: Bare Root or Potted Plant Perennial

How to Plant

Planting Bare Root Plants:

  • Select a location in full sun with a well amended soil that is evenly moist. Make sure there is good air circulation.
  • Prepare the bed by turning the soil under to a depth of 6-12, inches removing any debris, and lightly raking as level as possible.
  • The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
  • Dig a hole deep and wide enough to accommodate the bare root.
  • Set the plant such that the crown is at or just slightly below the ground level. Allow roots to fan out from the crown at around a 45 degree angle. Roots should spread out separately, like stretched fingers, from the crown, and not bunch up. It may be helpful to build a cone-shaped mound of soil in the bottom of the hole and spread the roots around it. It is important to set the roots such that the crown is roughly level with the ground.
  • Cover the roots with soil and tamp down firmly to get rid of air pockets. Fill the soil to just below the crown, where the top growth and leaves will emerge. Make sure all the roots under the crown are in good contact with the soil.
  • Water well to fully saturate the roots and soil.
  • Wait until new growth starts to appear before applying a layer of mulch.

Planting Potted Plants:

  • Select a location in full sun with a well amended soil that is evenly moist. Make sure there is good air circulation.
  • Prepare the bed by turning the soil under to a depth of 6-12, inches removing any debris, and lightly raking as level as possible.
  • The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
  • Plant on a cloudy day or in late afternoon to reduce transplant shock.
  • Dig a hole for each plant large enough to amply accommodate the root ball.
  • Unpot the plant and gently loosen the root ball with your hands to encourage good root growth.
  • Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
  • Use the plant tag as a location marker.
  • Thoroughly water and apply a light mulch layer on top of the soil (1-2 inches) to conserve water and reduce weeds.

How to Grow

How to Grow

  • Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their germination.
  • Mulches also help retain soil moisture and maintain even soil temperatures. For perennials, an organic mulch of aged bark or shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time.  Always keep mulches off a plant’s stems to prevent possible rot.
  • Careful watering is essential in getting perennials off to a good start. Water thoroughly at least once a week to help new roots grow down deeply. Soil should be damp at about 1 inch below the soil surface. You can check this by sticking your finger in the soil. Water early in the morning to give all leaves enough time to dry. One inch of rain or watering per week is recommended for most perennial plants. You can check to see if you need to add water by using a rain gauge.
  • Until plants become established, some protection from extreme winds and direct, hot sunlight may be necessary. Good air movement is also important.
  • After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
  • “Deadhead”, remove spent flower heads to encourage continuous flowering and prevent seed development.
  • Remove and discard foliage after a hard frost in fall.
  • In colder regions, apply another layer of mulch (1-2 inches) after the ground freezes in fall. Evergreen boughs (from Christmas trees) provide additional protection. Remove this mulch in the spring.
  • Divide in spring every three to four years to avoid overcrowding.
  • Plants may need staking; stake entire plant up to the flowers.

Growing tips

Growing Tips

  • To control height, delay bloom and increase the number of blooms, pinch plants back by ½ of their height in late spring/early summer.
  • Many gardeners do not cut back perennial flower seed heads in the fall, but wait until early spring before the new foliage appears. This provides food for wildlife over the winter.
  • Avoid overhead watering and divide clumps before plants get overly crowded.
  • Plants are intolerant of dry spells.
  • Harvest phlox flowers when 1/3-1/2 of the flowers in the panicles are open.

Common Pests and Problems

Common Disease Problems

Aster Yellows: Plants are stunted, develop witch's brooms (excessive growth), petals turn green and become deformed. This virus-like condition is spread by leafhoppers. Burpee Recommends: Remove infected plants and control leafhoppers. Remove weeds in the area which serve as alternate hosts to the disease.

Curlytop: This is a virus disease that is characterized by yellowing, stunting and eventual death of plants. It is spread by leafhoppers. Burpee Recommends: Control the leafhoppers which spread the disease and remove and destroy infected plants.

Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Some phlox varieties are resistant. Contact your Cooperative Extension Service for fungicide recommendations.

Root Rots: A number of soil borne pathogens cause root rots. Burpee Recommends: Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.

Septoria Leaf Spot: This diseaseis most severe during rainy seasons in closely planted gardens. Circular spots with gray centers and dark margins appear on the lower older leaves. Fungal spores are produced and darken the center of the spots. Burpee Recommends: Remove and destroy infected plant debris. Don't handle or brush against plants when they are wet. Rotate plantings. Remove weeds growing nearby.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects that can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Leafhoppers: Leafhoppers cause injury to leaves and stunt growth. They also spread disease. Burpee Recommends: Remove plant debris. Use insecticidal soaps. Consult your Cooperative Extension Service for other insecticide recommendations.

Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.

Stalk Borer: The larvae of this insect tunnel up and down inside the plant stem causing the plants to wilt. By the time the plant wilts it is too late to save it. The larva is 1.5 inches long, greyish brown with one dorsal stripe and two lateral stripes on each side. The lateral stripes on the front half are interrupted and the lower brown stripe extends forward onto the side of the head. The eggs hatch in May to early June, after the moth lays them the previous September or October. Burpee Recommends: Remove and destroy all plant debris and nearby weeds.

Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.

FAQ

Phlox FAQs

What are the white spots on the foliage of my phlox? It is most likely powdery mildew, a very common disease of phlox. Remove infected leaves and destroy them, and make sure your plants have excellent air circulation. Some varieties, such as 'David', are resistant.

Can phlox be used as cut flowers? Yes, they make great cut flowers.

Is phlox deer resistant? Yes, it can be fairly deer resistant.

Does phlox attract pollinators? Absolutely! Butterflies and moths are attracted to phlox, as well as bees and hummingbirds.

How can I use phlox in my garden? Use it in the border, as a cut flower, in a wildflower garden.

 

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