The Wilting of Garden Phlox

Brilliant color can be hard to come by in the late summer garden, making phlox (Phlox paniculata), with its blooms that can last into the beginning of autumn, a valuable plant. Blooming atop green foliage in solid hues and bi-colors, garden phlox blossoms appear in pinks, white, blues, purples, peaches and lavender. Unfortunately, these perennials are susceptible to problems that may harm the plants cosmetically and physiologically. When phlox plants wilt, it is a symptom of a larger problem. Snap into action to prevent permanent damage.

Preventive Care

Provide excellent care to garden phlox as a means of preventing problems and providing plants with the strength to recover quickly. Grow garden phlox in areas that offer full sun to partial shade for best growth. Garden phlox plants thrive in moist, well-drained soil high in organic content. Gardeners should irrigate soil when the top layer feels dry to the touch to prevent both dryness and waterlogged conditions. These perennials perform best in U.S. Department of Agriculture hardiness zones 4 to 8, and in warmer zones where temperatures are not extreme and the air is humid.

Improper Watering

Improper watering is often the cause of wilting in garden phlox. When the soil is dry for extended periods of time, plants cannot receive adequate moisture or the nutrients they receive through an uptake of water. On the other side of the coin, plants left in standing water may drown. In the case of drowning, plants are so full of water that they no longer have the ability to take in fresh water or nutrients. Improper watering leads to the wilting of plant foliage as well as the discoloration of leaves, which typically die and fall from the plant. Roots die as a result of over-watering. The garden phlox becomes more susceptible to infections and pest infestations; plants may collapse and die. To control wilting due to improper watering, simply scale back or water more often so soil remains moist without drying out completely or becoming excessively saturated. Gardeners should also improve soil drainage when gardening with heavy soils by mixing compost into the top layer of soil. In addition, a 2- to 3-inch layer of organic mulch, such as wood chips, helps slow the speed at which water enters soil while helping conserve absorbed moisture. Avoid pressing mulch against plant stems.

Phlox Plant Bugs

Pests such as the phlox plant bug (Lopidea davisi) may also lead to wilting in garden phlox. These bugs have tiny orange bodies as nymphs and black-and-orange bodies measuring approximately 1/5 inch long as adults. These pests feed on flowers, leaves and stems by sucking out plant fluid. Phlox plant bug infestation symptoms typically begin with a display of white-hued flecks on foliage. As the disease progresses throughout summer and early fall, leaves wilt, turn brown, die and fall to the ground. To control phlox plant bugs, apply a botanic pesticide such as insecticidal soap to the entire plant. However, if this low-toxicity measure is ineffective, an application of a pesticide with the active ingredient acephate offers stronger control.

Black Root Rot

Garden phlox is susceptible to a disease called black root rot. Caused by the fungal pathogen Thielaviopsis basicola, this disease often lives in soil for years. It is most partial to a soil pH between 5 and 8.5 and thrives in soil temperatures between 55 and 70 degrees Fahrenheit. Infected phlox plants display yellowing, wilting, leaf drop and slowed growth. As the disease progresses, roots begin to decay and display black areas of dying plant tissue. To control black root rot, maintain sanitary conditions in the garden, particularly by sterilizing tools before moving to a new plant. Applications of a fungicide with an active ingredient such as thiophanate-methyl offer effective control when applied at the first sign of a problem. However, gardeners may need to contact a licensed professional as this fungicide may be unavailable for home use.

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