Growing Phlox in Iowa

Care and How To

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.  There are over 60 phlox species native to North America. While many of these species are suitable for Midwestern gardens, below are a few species that are the most popular for Iowa Landscapes. 

Garden Phlox

Photo of violet Phlox paniculata
Garden Phlox (Phlox paniculata) Photo by Cindy Haynes.

Garden phlox (Phlox paniculata) is the most widely grown phlox species in home landscapes.  Plants range in height from 1 ½ foot tall to over 5 feet tall. Blooms first appear in mid-June in Iowa and may last for a month or more. Flower colors include lavender, white, orange/peach, pink, red, and many with light or darker centers or "eyes". This prairie native prefers sunny sites with moist, well-drained soils and good air circulation. Plants often tolerate part sun and watering may be necessary during hot, dry periods. While the species itself is seldom grown in gardens, numerous cultivars are available. 

Planting and Dividing Garden Phlox

Garden phlox can be divided in spring or late summer/early fall.  In spring, dig up the plants just as new growth begins to appear.  Divide each clump into sections with each division containing at least 2 or 3 shoots and a portion of the root system.  Replant the divisions immediately.  Keep the newly divided perennials well watered through spring and summer. 

When dividing in late summer/early fall (mid-August through September), dig up the entire plant, divide and replant as you would for spring division.  Plants divided in late summer/early fall should be mulched in late fall (November).  A 4- to 6-inch-layer of straw, pine needles, or similar material should prevent repeated freezing and thawing of the soil that could heave late summer/early fall planted divisions out of the ground and cause severe damage.  Remove the mulch in early spring (March).   

Powdery Mildew on Garden Phlox

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.  While this disease can be managed with frequent and regular fungicide applications, this is often not desirable for the gardener because of the amount of time, money, and chemical involved. 

The best way to minimize powdery mildew problems is by selecting mildew-resistant cultivars.  Several trials have been done over the years to determine which selections are best for the landscape. Performance was based on many factors including (but not limited to) flower production and incidence of powdery mildew.   Below are some of the top-rated cultivars from the Chicago Botanic Garden and Mt. Cuba Center trials of garden phlox listed by height. This doesn't mean you shouldn't try other garden phlox cultivars. Some of the newest cultivars haven't been in production long enough for sufficient testing and powdery mildew may arise (or maybe not!).

Recommended Cultivars of Garden Phlox

Cultivar Flower Color Height x Width (inches) Powdery Mildew Resistance
Coral Flame™ ('Barsixtytwo') coral 18x18 good
'Forever Pink' pink 24x32 excellent
'Bill Baker' pink 24x36 excellent
'Morris Berd' pink 24x36 excellent
'Minnie Pearl' white 24x36 excellent
'Kim' pink 24x48 excellent
'Fondant Fancy' bright pink, magenta eye 25x27 good
'Wendy House' bright red purple 26x20 excellent
Pink Flame™ ('Bartwelve') ** salmon pink, darker eye 27x22 excellent
N3 Springfall ('N3 tasahce rvfo hakof') pink 28x36 excellent
'Laura' purple, white eye 30x20 good
Purple Flame™ ('Barfourteen') pinkish purple 30x24 good
'Fancy Feelings' deep pink 30x24 good
'Peppermint Twist' pink and white 32x31 excellent
'Babyface' pink, dark eye 32x32 good
'David' white 34x24 good
'Orange Perfection' orange, magenta eye 36x24 good
'Glamour Girl' coral pink 36x30 good
'Blue Paradise' violet blue 36x30 good
'Pink Lady' pink, white eye 36x30 good
'Crème de Menthe' light pink, darker eye 36x30 good
'Inta' pink, darker eye 37x34 good
'Kraftprotz' deep pink 38x34  good
'Katherine' lavender, white eye 38x36 good
'Karmin Grand' rose red 39x32 good
Ice Cap™ ('Dasfive') white 40x24 good
'Frosted Elegance'  pale pink, darker eye 40x30 excellent
'Speed Limit 45' light pink   44x30 good
'LSS Vincent' pink 44x30 good
'Lavelle' white, pink tube 48x36 good
'John Fanick' pink two-tone 48x46 good
'Shortwood' ** rosy pink   50x34 excellent
'Dick Weaver' magenta 50x36 good
'Delta Snow' white, purple eye 52x40 good
'Robert Poore'  purple 54x40 good
'Lichtspel' pink, red eye 57x34 excellent
'Jeana' ** pink 60x48 excellent

** Highly Recommended.  
The entire list of trialed garden phlox, including those that performed poorly, can be found at the Chicago Botanic Garden website and the Mt. Cuba Center website.

 

photo of Phlox 'Peppermint Twist' in bloom.
Phlox 'Peppermint Twist' in bloom.  Photo by Cindy Haynes.

Spotted Phlox (Phlox maculata)

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.  Recommended cultivars include:

  • ‘Alpha’ (rose-pink flowers with darker eyes)
  • ‘Natascha’ (pink and white striped flowers)
  • ‘Omega’ (white flowers with pink eyes)
  • ‘Rosalinde’ (purple-pink flowers)

Woodland Phlox (Phlox divaricata)

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.  Rabbits love woodland phlox.  Plants may need to be protected with fencing during establishment.  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)
  • ‘May Breeze’ (white flowers)
  • Phlox divaricata subsp.  laphamii ‘Chattahoochee’ (lavender blue flowers with dark purple centers)

Prairie Phlox (Phlox pilosa)

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. 

Photo of white and purple Phlox subulata
White and purple moss phlox (Phlox subulata). Photo by Cindy Haynes

Moss Phlox (Phlox subulata)

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.  Moss phlox 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. Excellent cultivars include:

  • 'Amazing Grace’ (white flowers with magenta eyes)
  • ‘Drummond’s Pink’ (deep pink flowers with darker eyes)
  • ‘Emerald Blue’ (lavender blue flowers)
  • ‘Emerald Pink’ (bright pink flowers)
  • ‘Scarlet Flame’ (magenta red flowers)
  • 'White Delight’ (pure white flowers)

Creeping Phlox (Phlox stolonifera)

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. Creeping phlox is an excellent groundcover and edging plant.  Excellent cultivars include:

  • ‘Blue Ridge’ (lavender-blue flowers)
  • ‘Home Fires’ (pink flowers)
  • ‘Pink Ridge’ (lavender-purple flowers)
  • ‘Sherwood Purple’ (purplish blue flowers)

 

Updated from articles that originally appeared in the May 24, 2019 and July 14, 2010 issues of Horticulture and Home Pest News.

Scientific Name: 
Authors: 

Cynthia Haynes Professor

Dr. Haynes is a Professor of Horticulture at Iowa State University in Ames.  Her primary responsibilities are in teaching and extension.  She teaches several courses for the Department of Horticulture including Home Horticulture and Herbaceous Ornamentals.  She also has extension r...

Aaron Steil Consumer Horticulture Extension Specialist

Aaron Steil is the consumer horticulture extension specialist at Iowa State University where he works with county Extension offices across the state to answer home gardening questions for all Iowans.  This includes information related to trees, shrubs, vegetables, fruits, herbs, perennials, ...

Last Reviewed: 
July, 2022