PHLOX: AN EXPLORATION

PHLOX SPECIES AND CULTIVARS

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Introduction

What is a Phlox?

Horticultural History

Basis of Breeding

List of Medium-size Phlox

List of Moss Phlox

References



In this section I will discuss the species and cultivars of Phlox primarily from a horticultural and natural history point of view. I am using genus section divisions that reflect that rather than strict taxonomy and listing species and cultivars alphabetically within each section for the sake of ease of reference. For botanical descriptions and keys see Wherry 1955 and other texts. In general the taxonomy follows the USDA Plants Database, except for P. ovata, which has recently been changed back from P. latifolia. There is excellent information on cultivation and propagation of the smaller phlox in Foster and Foster 1990.

     Large Phlox  
These species seem to fall into two natural groups, which I will call the paniculata-maculata group and the ovata-pulchra group.

Paniculata-Maculata Group
These species have foliage that in fall dies down completely or to short overwintering shoots (at least in USDA Zone 6 and north). Seed germination occurs within a year of sowing, sometimes without chilling. The cotyledons are noticeably narrower in proportion than in the next group. Seedlings usually bloom the first season. All chromosome counts I know of have been 2n=14, except for P. maculata 'Miss Lingard,' which is a triploid.

Phlox amplifolia
(Large-leaf phlox) - Range: Southern Midwest, Indiana to Alabama, west to Missouri. Habitat: moist open woods and roadsides. Bloom time: late spring to early summer. Height: to about 150cm. Flower color: pink to purple. Bloom time: late spring to early summer. This species has not been used horticulturally and is related to P. paniculata, as evidenced by the presence of marginal veins in the leaves. In Tucker Co., northern West Virginia, there is a phlox that has been referred to as P. amplifolia in the West Virginia checklist and atlas but differs in that the leaves are wide-linear rather than rhomboidal, and the inflorescence lacks glandular pubescence. This blooms in early June and has pink-purple flowers.

Phlox carolina (Carolina phlox) - Range: North Carolina to southern Illinois and south to the Gulf of Mexico. Habitat: open woods and meadows. Height: from 45cm to about 200cm. Bloom time: spring to late summer. Flower color: pink to red-purple. The flowers are borne in loose, dome-shaped panicles. Current taxonomic treatments of P. carolina make it a variable species that includes widely differing forms. In practical terms it has been treated as a bin for forms that do not fit into the other species. Wherry recognized four subspecies that have widely overlapping ranges. Individual plants of all of these are described as having a few upright flowering shoots and rare sterile shoots.
     P. c. subsp. carolina is described by Wherry as having "bright green" (ie yellow-green), relatively wide lanceolate leaves (10-30mm wide X 50-100mm long), and blooming late spring into summer. There is a confusing assemblage of forms that appear to belong to this taxon. All of these have lanceolate foliage on erect stems 60 to 90cm tall and bloom mid spring to mid summer. The plant growth habit varies from clump-forming to vigorously stoloniferous. 
       'Kim' - This is 45-60cm tall with light pink-purple flowers in irregular panicles. The plants are vigorously stoloniferous with many relatively lax sterile shoots. 'Kim' was found wild in Alabama and introduced by Jan Midgley. 
       'Lil' Cahaba' - Listed by Plant Delights Nursery from Bibb Co., Alabama, this is relatively slender and 60cm tall. It has "pinky-mauve" flowers in early to mid summer. It was collected by Jan Midgley along the Little Cahaba River.
       'Minnie Pearl' - This beautiful selection was found in Kemper Co, east-central Mississippi. It has usually been considered a wild hybrid, but I think I will agree with Peter Zale at the OSU Germplasm Center that it is straight P. carolina. It is about 60cm tall and spreads to form a thick patch. There are masses of large white flowers for a long period from late spring into summer. I would rate 'Minnie Pearl' as the best early-blooming large phlox, since it has always thrived for me under adverse conditions in the garden and neglected in containers, always blooming well and free from mildew.
     P. c. subsp. alta is limited to the southern Appalachians and has dark green foliage and blooms later, mid to late summer. The leaves are more rounded than those of ssp. carolina. Wherry describes this as "massive" and up to 200cm tall, but mine are about 100cm tall in bloom. This is the only P. carolina I have seen in nature. This was in the Blue Ridge of western North Carolina, where it grows most commonly along the Blue Ridge Parkway near Asheville at 4000 to 5000ft on roadside banks and in openings in well-drained acid soil, blooming in July and August. The plants are about 75 to 110cm tall and tend to have purplish stems. There are photos on a separate page. This is a very different habitat from those of P. g. ssp. glaberrima and P. glaberrima ssp. interior and P. maculata. My garden plants tend to have red-purple stem and new foliage coloration and form flower buds under cool greenhouse conditions in May, blooming from June until late summer.
     P. carolina ssp. angusta of southern lowlands is small and wispy, with narrow (about 4mm maximum) leaves, and looks to me more closely related to P. glaberrima than P. carolina. My plants are the cultivar 'Gypsy Love' and bloom from late spring into summer. 'Gypsy Love' is a selection made by Gateway Gardens in Delaware that is 45-60cm tall and has red-purple flowers resembling those of typical P. glaberrima.
     
Phlox "amplifolia," Canaan Valley, WV
Phlox carolina ssp. alta
Phlox carolina 'Kim'
     P. carolina subsp. turritella is another southern lowland type with wider leaves that are largest around the middle of the stem and gradually reduced to the apex to form a cone. It blooms in summer. I have not seen any plants referrable to this taxon.
A few other cultivars have been distributed under the name Phlox carolina:
     'Bill Baker' see P. triflora 'Morris Berd'.   
     'Magnficence'- All of the plants I have seen appear to be P. maculata 'Alpha'. I do not know if there is another plant that is different.
     'Miss Lingard' see P. maculata 'Miss Lingard'.

Phlox glaberrima ssp. glaberrima and ssp. interior (Smooth phlox) - Range: Virginia to Illinois south to Tennessee and Arkansas. Habitat: moist open woods to marshes. Height: 40to 150cm. Bloom time: late spring to early summer. Flower color: pink to purple. The flowers are borne in very open panicles. These are narrow-leaved, long-stemmed, gawky plants that require constant moisture to do well in cultivation.
     'N Springfall' is a selection from Nearly Native Nursery in Fayetteville, GA. This is about 75cm tall with red-purple flowers in early summer. The nursery calls it a "strange form," but it is similar to other P. glaberrima we have seen. It is also supposed to bloom into the fall but did not do well for us and died down by September, probably because the site was too dry.

Phlox idahonis (Idaho phlox) - Range: central Idaho. Habitat: moist, grassy meadows. Height: 50 to 100 cm. Bloom time: early summer. Flower color: lilac to lavender. This is a narrow endemic that has never entered horticulture. It appears to be related to P. maculata and P. carolina.

Phlox carolina 'Minnie Pearl'
P. glaberrima ssp interior crown lacks decumbent stems P. triflora decumbent stem (arrow) Phlox glaberrima ssp. interior
Phlox maculata (Meadow phlox) - Range: southern Quebec to northern Georgia west to Minnesota and Missouri. Habitat: moist meadows and stream banks. Height: 60 to 120cm. Flower color: Purple-pink. Bloom time: late spring to mid summer. This species is distinguished by its cylindrical inflorescence and maroon-spotted stems. There are two recognized subspecies: P. m.ssp. maculata has fewer leaf nodes and blooms late spring to early summer; P. m. ssp. pyramidalis has more numerous leaf nodes and blooms in mid summer. The latter appears to be derived from hybridization with P. glaberrima (Levin 1963). Locklear (2011) seems most familiar with P. maculata from midwestern fens and treats it as a species primarily of wet calcareous soil, but in the Appalachians I have found it only in acid soils in wet fields and along streams. Plants I have grown from Pennsylvania and West Virginia have a few tall flowering stems (to about 120cm) and are non-spreading. Those I have bought from Prairie Nursery in Wisconsin are shorter (to about 75cm) and form patches. These took several years to bloom, but last summer (2013) made bushy plants with many flower stalks. None of the named cultivars has a growth habit like that of the Prairie plants. It is difficult to assign garden cultivars to one subspecies or the other. All of the following cultivars are badly afflicted with mildew unless they are in moist or even wet soil with sun exposure.
     'Alpha' - This selection was raised and introduced by Georg Arends early in the 20th century. I am dubious that the form currently available in the US under this name is the true plant, since the flower color of 'Alpha' is described as "a soft but telling pink" (Bloom 1991) and that of the plant I have seen are a harsh magenta. This is about 90cm tall.
      'Miss Lingard' - This is usually listed in catalogs as P. carolina, but the cylindrical inflorescence indicates P. maculata.  It has been found to be a sterile triploid (Meyer 1944), but this need not indicate hybrid ancestry, as Locklear (2011) says. 'Miss Lingard' is a handsome pure white about 75cm tall.
     'Flower Power' (PP#17,551) - A seedling of 'Omega,' this vigorous cultivar was bred by Darrell Probst and introduced by Blooms of Bressingham. It has white flowers flushed with light pink-purple and reaches 90-120cm.
     'Natascha' is a form with the petals variegated with the center pink and margins white. This is essentially the same coloration as P. subulata 'Tamonongalei' aka 'Candy Stripe.'  
     'Omega' - This was introduced by Alan Bloom in 1966 and is about 90-120cm tall. The large white flowers have a light pink eye ring; 'Omega' is by far the most beautiful of the white P. maculata cultivars.
     'Rosalinde' - This is a cultivar about the same size as 'Miss Lingard', with magenta pink flowers. 

Phlox paniculata (Border phlox) - Range: Pennsylvania to Illinois and south to northern Georgia and Arkansas. Habitat: mainly in woods along streams and rivers. Height: 90-120cm. Flower color: pink to purple-pink. Bloom time: mid to late summer. P. paniculata is the phlox species that has been most subjected to breeding and selection. There are hundreds of cultivars, and I will not attempt to deal with them. References such as Armitage 2006 and Rice 2006 give good reviews. Selections are often falsely referred to as hybrids.    

Hybrids - Surprisingly few of the phlox garden cultivars of this group are hybrids. There have been persistent rumors that Georg Arends made P. paniculata P. maculata hybrids in the early 20th century and that these are part of the P. paniculata cultivar line-up. Arends may have made this cross, but no cultivar that I have seen could be a hybrid of this parentage. Arends is also supposed to have made crosses between P. carolina and P. maculata (Aniśko 2008), but these do not seem to be present in any obvious way in horticulture today.

     Arendsii hybrids - These are the result of crosses between P. paniculata and P. divaricata and are 30 to 60cm tall. The plants combine the relatively low stature of P. divaricata with the colors of P. paniculata garden selections. The original hybrid was bred by Georg Arends in the 1920s and is available today as 'Anya,' which has magenta pink flowers. New Dutch selections include 'Luc's Lilac' and the Spring Pearl Series ('Miss Jill,' 'Miss Karen,' 'Miss Margie,' and 'Miss Mary'), named for the office staff at the DeVroomen company, and with white, dark pink, lilac-blue, and rosy-red flowers,
respectively.
Phlox maculata along the Youghiogheny River, Fayette Co., PA
Phlox maculata Prairie form

Phlox maculata 'Flower Power' wild-type Phlox maculata cylindrical inflorescence Phlox ovata




Ovata-Triflora Group
The fertile portions of the stems of these species die back in fall leaving an evergreen clump of basal foliage from which flowering stems arise the next season. Seed germination is extended over at least two years, with about half occurring the second year. Cotyledons are relatively broad. Seedlings wait until the second season to bloom. At least some populations of P. triflora and P. pulchra are tetraploid (C. Ferguson, pers. comm.; P. Zale, pers. comm.).

Phlox ovata
(Wide-leaf phlox) - Range: Pennsylvania to northern Georgia; Ohio and Indiana. Habitat: moist to dry open woods. Height: 30 to 45cm. Bloom time: late spring. Flower color: pink to pink-purple. This species has ovate leaves arising from thick procumbent stems and attractive flowers in flat-topped panicles. It has done well for us in a sandy raised bed in partial shade. This species is hardly ever seen in gardens, but there seems potential for selection of attractive clones. This species may not be closely related genetically to the triflora-pulchra series but resembles it in growth habit.

Phlox pulchra (Alabama phlox) - Range: north-central Alabama. Habitat: margins or openings in woodland. Height: 25 to 50cm. Flower color: pink to purple.  This species has ovate leaves and a growth habit similar to that of P. ovata. It is undeservedly almost unknown in gardens. At the present time the only nursery source I can find in the US is Plant Delights, who list a clone from Bibb Co., Alabama, as 'Bibb Pink.'
     'Eco Pale Moon' - This selection from Don Jacobs at Eco Gardens has light pink flowers.
     'Spring Delight' - This is about 45cm tall and blooms in late spring with magenta flowers. In catalogs it is often referred to as a hybrid between P. paniculata and P. stolonifera, but this seems very unlikely, and it seems to be just a mediocre P. pulchra. There is a fairly similar, but much more attractive plant distributed by Don Hackenberry of Appalachian Wildflower Nursery. I no longer have the plant and do not remember what name he used for it.
Phlox pulchra
Hybrid (?) phlox from Don Hackenberry



Phlox 
triflora (Three-flower phlox) - Range: Maryland to Indiana, south to Georgia and Alabama. Habitat: open woods. Height: 40 to 60cm. Bloom time: late spring. Flower color: pink to purple. The flowers are borne in groups (cymes) of three in a nearly flat-topped panicle. Judging by all the garden material I have seen, this taxon seems to have little to do with P. glaberrima and is probably a separate species more closely related to P. pulchra. Wherry's (1955) key uses the trait of flowering shoots arising from decumbent stems to separate P. pulchra and P. ovata from the other tall phlox, and by this P. triflora belongs with those two species. I do not understand why he could have considered it a subspecies of P. glaberrima. This naturalizes well in garden situations, since it will self-sow into drifts and thrives in a range of well-drained soils in sun to partial shade. P. triflora, P. ovata, and P. pulchra have been confused in botany and horticulture, and their genetic relationships are not yet clear. 
     'Anita Kistler' - This is similar to 'Morris Berd,' but the flower color reportedly tends toward lilac.
     'Bill Baker' appears to be the same clone as 'Morris Berd' (below) taken to England and named there.
     'Forever Pink' is a new selection bred by Jim Ault at the Chicago Botanic Garden and not yet introduced. This is described as a cross between Phlox glaberrima ssp. triflora and Phlox 'Bill Baker' and its long period of bloom attributed to hybrid sterility, although unless Ault has something different from what I grow under the name 'Bill Baker,' it should be simply P. triflora.
     'Morris Berd' - This selection has become a deservedly popular garden plant. It differs from the wild type in having larger flowers of a more pleasing pink. The original plant was given to Morris Berd by Edgar Wherry and later introduced by Don Hackenberry of Appalachian Wildflower Nursery. According to Morris Berd, it was considered P. pulchra by Edgar Wherry, but in all respects it is P. triflora, and there must have been an i.d. mix-up at some time.    
     'Triple Play' is a variegated form with white-margined leaves from Joe Pye Weed's Garden in Massachusetts.

Other Entities - At the present time (February 2014) I have three quite different plants that are being sold as P. carolina and that seem to belong here.
     Mulberry Woods form - The first is from Mulberry Woods Nursery in Hayden, Alabama, and was collected along the Mulberry Fork River. My plant is lax in habit, about 60cm tall, and bloomed for the first time in midsummer 2013 with magenta-pink flowers.
     Growild form - This came courtesy of the OSU Germplasm Center from stock from Growild Nursery in Fairview, Tennessee. There is no record of the source of the original plants. My plants are erect and about 75cm tall and have large, round pink flowers in late spring. As the flowers mature the styles lengthen, becoming exserted to an unusual degree and upcurved. The evergreen basal foliage is rounded like that of P. pulchra.
     Growing Wild form - My plants are from Growing Wild Nursery in Burgaw, North Carolina, from stock collected in Jones Co., NC. This resembles P. triflora, but the flowers are in cymes of two to five flowers rather than three. In addition the fertile stems remain erect in late summer, rather than falling and rooting down, as in P. triflora. The collection site is in southeastern North Carolina, outside the range of P. triflora, and accounts for the disjunct county record for P. carolina on the USDA Plants Database range map.







     (next page - Medium phlox)
Phlox triflora
Phlox "carolina" Growild form


                   

[Introduction] [What is a Phlox?] [Horticultural History] [Basis of Breeding] [Accounts of Species and Cultivars] [References