Phlox bloom profusely from midsummer to fall creating a mass of color. These highly fragrant flowers range in color from white to shades of pink, lavender, purple and bi-colored blooms. Grown in the background, phlox create an excellent backdrop to smaller plants and reach heights of 2-½ to 3 feet. Phlox return each year in larger clumps, needing division every few years to encourage vigorous growth and abundant blooms.
Select a sunny location for phlox. Six to 8 hours of direct sunlight is best, but phlox tolerate partial shade. Reduced bloom size and pale color result if phlox do not receive adequate light.
Plant phlox in well-drained soil rich in organic matter. Till the soil to a depth of 8 to 10 inches, and add generous amounts of well-rotted manure or garden compost to the soil. Mix in well with existing soil. An addition of balanced fertilizer (10-10-10) is beneficial. Follow the recommended application rate on the package. Mix the fertilizer in well to prevent injuries to young roots.
Place the phlox plant in the soil so that the crown of the plant is 1 inch below the surface of the soil. Plant nursery specimens at any time up until frost. Bare roots purchased from mail order companies require planting several weeks before the first frost to allow roots to form and the new plant to become established.
Mulch newly planted phlox for the first winter or two to prevent damage from harsh weather. Mature phlox benefit from winter mulching, but will survive without it. Mulch not only protects the plants from winter damage, it prevents plants from sending up new shoots during brief warm spells before the weather is warm enough to sustain phlox.
Water thoroughly when soil dries. Phlox thrive in moist soil and benefit from an application of water once a week. Apply water to the roots and avoid getting the foliage wet to discourage disease. If wetting the foliage is unavoidable, water early in the morning allowing foliage to dry in the summer sun.
Fertilize in spring when the first flush of new growth appears and repeat an application just before blooming. Water-soluble fertilizer designed from blooming flowers provides the nutrients phlox require.
Deadhead blooms to encourage continued blooming. Once flowers have faded and the plants stop producing blooms, cut phlox back by several inches. This often produces a second flush of smaller blooms.
Divide roots every 2 to 3 years by digging the plants and separating into several clumps. Replant to the original depth in a new location.