Perennial Phlox for Home Landscapes

Selecting perennials for the home garden can be a bit intimidating as there are hundreds of plant species and innumerable cultivars available.  Among those that deserve consideration are several species of Phlox (The word phlox is Greek meaning flame and refers to their brightly colored flowers).

Garden phlox (Phlox paniculata) is the most widely grown phlox species in home landscapes.  Garden phlox is a clump-forming, upright plant which produces large, showy flower clusters in summer.  Plants are generally 2 to 4 feet tall.  While the species itself is seldom grown in gardens, numerous cultivars are available.  Gardeners can choose from white, pink, red, blue, and purple flowering cultivars.  Unfortunately, many cultivars of garden phlox are susceptible to powdery mildew.  Powdery mildew produces a grayish white coating on the stems and leaves of infected plants.  Infected leaves turn yellow and eventually dry up and turn brown.  Severely infected plants are unsightly.  Good cultural practices, such as adequate plant spacing and the removal of infected plant debris in fall, can reduce the severity of powdery mildew.  Gardeners can also minimize powdery mildew problems by selecting mildew resistant cultivars.  Cultivars that possess good to excellent mildew resistance include ‘David’ (white flowers), ‘Laura’ (purple flowers with white eyes), ‘Orange Perfection’ (orange flowers), ‘Robert Poore’ (magenta flowers), and ‘Wendy House’ (reddish purple flowers).  Garden phlox grows best in moist, fertile, well-drained soils in partial to full sun.  Watering may be necessary during hot, dry periods. 

A picture illustrating purple Phlox paniculata
A picture illustrating purple Phlox paniculata. Cindy Haynes, Department of Horticulture

Spotted phlox (Phlox maculata) is similar to garden phlox in appearance and cultural requirements.  However, there are several differences.  Spotted phlox is earlier flowering, has darker green leaves, conical flower heads, and better mildew resistance.  Plants are generally 2 to 3 feet tall.  Spotted phlox is native to Iowa.  It is most commonly seen along roadsides and prairie swales in northeast Iowa.  The species has mauve-pink flowers.  Cultivars include ‘Alpha’ (rose-pink flowers with darker eyes), ‘Natascha’ (pink and white striped flowers), ‘Omega’ (white flowers with pink eyes), and ‘Rosalinde’ (purple-pink flowers). 

Another native Phlox species is woodland phlox (Phlox divaricata).  It is commonly found in moist, partially shaded woodland sites.  Woodland phlox produces loose clusters of fragrant, blue to violet flowers in spring (April to June).  Plants are typically 12 to 15 inches tall.  Woodland phlox is an excellent plant for woodland gardens.  It can also be used in the front of perennial beds or planted in clumps amongst other low-growing, shade tolerant perennials.  Attractive cultivars include ‘Blue Moon’ (lavender blue flowers), ‘Clouds of Perfume’ (lavender blue flowers), ‘Fuller’s White’ (grows 8 to 12 inches tall, white flowers), ‘Louisiana Blue’ (purple flowers), and ‘May Breeze’ (white flowers).  ‘Chattahoochee’ (Phlox divaricata subsp.  laphamii) has lavender blue flowers with dark purple centers.  Rabbits love woodland phlox.  Plants may need to be protected with fencing during establishment. 

Prairie phlox (Phlox pilosa) is a native prairie wildflower.  It is commonly found in open woods, prairies, and meadows.  Prairie phlox blooms from April to June.  Flowers vary in color from pale pink to rose to violet.  Plants stand 12 to 24 inches tall.  Prairie phlox is an excellent plant for sunny, dry locations, rock gardens, and natural areas. 

A common sight in many home landscapes in spring is the brightly colored flowers of moss phlox (Phlox subulata), commonly called “creeping phlox.”  Moss phlox forms dense, carpet-like mats.  Plants are 4 to 6 inches tall.  Its foliage is narrow, stiff, and needle-like in appearance.  Flower colors include white, pink, red, blue, and purple.  Excellent cultivars include ‘Amazing Grace’ (white flowers with magenta eyes), ‘Drummond’s Pink’ (deep pink flowers with darker eyes), ‘Emerald Blue,’ ‘Emerald Pink,’ ‘Scarlet Flame’ (magenta red flowers), and ‘White Delight.’  Moss pink is easy to grow.  It performs best in sunny areas and well-drained soils.  Shearing back plants after flowering promotes dense growth and some rebloom.  Moss phlox is useful for edging beds and as a groundcover for sunny slopes.  It also looks good planted amongst rocks or atop a wall. 

A picture illustrating white and purple Phlox subulata
A picture illustrating white and purple Phlox subulata. Cindy Haynes, Department of Horticulture

Another low-growing phlox is creeping phlox (Phlox stolonifera).  Plants grow 6 to 12 inches tall and bloom in spring.  Creeping phlox does best in moist, well-drained soils in partial shade.  Excellent cultivars include ‘Blue Ridge,’ ‘Home Fires’ (pink flowers), ‘Pink Ridge,’ and ‘Sherwood Purple’ (purplish blue flowers).  Creeping phlox is an excellent groundcover and edging plant.

When browsing in garden centers this spring, be sure to check out the species and cultivars of perennial phlox.  They are excellent plants for home gardens.

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