PHLOX: AN EXPLORATION

PHLOX SPECIES AND CULTIVARS

Primrose Path Home

Introduction

What is a Phlox?

Horticultural History

Basis of Breeding

List of Large Phlox

List of Moss Phlox

References
     Medium-size Phlox
Pilosa Group
Phlox amoena (Hairy phlox) - Range: southern Kentucky and western North Carolina south to northern Florida. Habitat: dry open woods. Height: 25 to 45cm. Bloom time: spring. Flower color: purple to pink. This has been a grudging grower for us in western Pennsylvania, not lasting more than a couple of years and probably not fully hardy. In general it is not as good a garden plant as P. divaricata or P. pilosa. Phlox ×procumbens, a hybrid between P. stolonifera and P. subulata, has been sold under the incorrect name P. amoena.
     'Cabot Blue' has flowers of a violet color.

Phlox divaricata (Wild blue phlox) - Range: southern Ontario to Minnesota and south to Georgia and Louisiana. Habitat: open woods. Height: 30 to 45cm. Bloom time: spring. Flower color: lilac to violet. There are two subspecies. P. divaricata ssp. divaricata of the East, with notched petals, meets P. d. ssp. laphamii of the Midwest, with unnotched petals, along a line from Illinois to Georgia, but within the wide range of each subspecies there is little geographic variation. This is in great contrast to P. pilosa. P. divaricata naturalizes very well in cultivation. There is a long list of named selections, although almost all of them could be matched to individuals within a large naturalized cultivated colony. Although it is a woodland plant, P. divaricata needs some exposure at least to dappled sun to be free of mildew in the garden. Some selections have been very short-lived in our garden, but they will seed abundantly if allowed.
     'Blue Elf' is a small selection about 15cm tall.
     'Blue Moon' has large blue flowers with wide petals.
     'Clouds of Perfume' is a hyperbolically named selection with lavender-blue flowers and about the usual amount of fragrance for the species. I would give it about a 4 on an olfactory scale from 0 to 10, where 10 is nose inside an Easter lily flower.
     'Dirigo Ice' has pale blue flowers.
     'Fuller's White' has pure white flowers and, if introduced into a naturalized colony will ensure that there are white individuals present ever after.
     'Louisiana' has purple-blue flowers with a reddish eye.
     'Parksville Beach' has purple-pink flowers.
Phlox amoena
an unnamed cultivar of Phlox divaricata
Phlox floridana (Florida phlox) - Range: Florida, Georgia, and Alabama. Habitat: sandy open woods. Height: 25 to 50cm. Bloom time: summer. Flower color: purple to pink. This is similar to subspecies of P. pilosa and has not entered horticulture.

Phlox longipilosa - Range: Oklahoma. Habitat: granite hills. Height: 20-45cm. Bloom time: late spring. Flower color: rosy-purple. This is a recently described narrow endemic and is not in horticulture, although it looks very attractive in photos (e.g. http://www.oknaturalheritage.ou.edu/RegistryNews_Spring2006.pdf).

Phlox pilosa (Downy phlox) - Range: Michigan and Wisconsin to Florida and Texas, and, separately, Connecticut to South Carolina. Habitat: open woods, prairies, along rivers. Height: 20 to 60cm. Flower color: pink to purple. Bloom time: late spring to early summer. There are a number of widely different subspecies included in P. pilosa, some much more garden-worthy than others. P. pilosa ssp. pilosa is the plant used in prairie restoration. Grown in the garden, this is thin and floppy. P. p. ssp. ozarkana is much better. There seems to be only one clone in horticulture, often referred to as 'Ozarkana,' which I am going to call 'Ozark Rose.' This forms a long-lived clump about 60cm tall and has abundant flowers of an old-rose color (closest to RHS red-purple 74D). It slowly spreads into a patch. P. p. ssp. riparia, from Texas, available as seed from Alplains, is about 20cm tall and has pink flowers. This did not last long for me and may not have been completely hardy in western PA.  P. pilosa ssp. sangamonensis from Illinois is a recently described subspecies with smooth stems and leaves. The plants distributed by Seneca Hill Nursery have red-purple flowers and are about 60cm tall. 
     'Eco Happy Traveler'  from Eco Gardens is a running form about 25cm high with dark pink flowers. This has barely survived for me and may not be completely hardy in the North.
     'Slim Jim' introduced by Plant Delights from a collection in East Texas has narrow hairy leaves and fragrant lilac flowers on stems to about 30cm. This runs to form a large, open patch. It may be P. pilosa ssp. pulcherrima, but Wherry's key does not work well for the plant.

Hybrids - P. amoena and P. divaricata cross in nature to make the hybrid P. ×rugelii. This hybrid has arisen spontaneously several times in my garden. An artificial cross that I did resulted in a vigorous 30cm-tall purple-flowered hybrid that I named 'Charles' Passion' (it bloomed in the greenhouse at Eastertime) and introduced in 1991. 'Green Spring' is a compact (to about 20cm) hybrid with pink-purple flowers raised by Don Humphrey at Green Spring Park in Falls Church, VA, in the 1990s.
     P. divaricata and P. pilosa hybridize in nature (P. ×glutinosa). The cultivar P. 'Chattahoochee' from northern Florida is supposedly a hybrid of this cross, but Wherry (1955) considered the original introduction to be P. divaricata ssp. laphamii. Plants I have bought under this name have been P. divaricata.
     Natural hybrids between P. pilosa and P. amoena have been found in Alabama and Tennessee (Levin and  Smith 1966).  These have not entered horticulture. Hybridization may be the origin of some of the subspeciation in these plants.
     Hybrids between P. divaricata and P. paniculata (P. ×arendsii) are discussed under P. paniculata.
     P. amoena and P. bifida seem to hybridize in a couple of sites in Tennessee and Kentucky. These forms have not made it into horticulture.
Phlox pilosa ssp ozarkana
Phlox pilosa ssp sangamonensis
Phlox pilosa ssp. riparia from Alplains Phlox pilosa 'Slim Jim' Phlox ×rugelii 'Green Spring'
Drummondii Group
This is a group of three species, all of which are annuals, germinating in late winter and blooming through the spring and early summer.

Phlox cuspidata - Range: Southern Oklahoma to Texas. Habitat: grassland and open woods. Height: 5 to 25cm. Flower color: purple to lilac. Bloom time: spring. Not in cultivation.

Phlox drummondii (Annual phlox) - Range: Texas. Habitat: grassland. Height: 10 to 50cm. Flower color: red to purple or lavender. Bloom time: spring to early summer. This has become a popular annual, available as seed or plants at garden centers. Seed mixes produce a wide range of flower colors and plant sizes, but apparently only in the Intensia series is this due to hybridization with other species, although selected types are often referred to as hybrids.

Phlox glabriflora - Range: southern Texas. Habitat: Sandy grasslands. Height: 10 to 45cm. Flower color: purple to lilac. Bloom time: spring. This is one parent of the annual phlox hybrids known as the Intensia series.

Hybrids - Hybrids have been made between P. drummondii and P. paniculata. These do not seem to be extant at this point.
     The new Intensia series are F1 hybrids between P. glabriflora and P. drummondii.

Stolonifera Group
These two species are nearly prostrate running woodland plants.

Phlox adsurgens (Periwinkle phlox) - Range: Oregon to California in the Cascades. Habitat: woodland, 500 to 6000 ft. Height: to about 15cm. Flower color: purple to pink. Bloom time: spring. This is a very beautiful plant, especially the forms with full, peach-pink flowers. Unfortunately, it does not grow well in the Eastern US.
 
Phlox stolonifera (Creeping phlox) - Range: Pennsylvania to Georgia in the Appalachians. Habitat: woodland. Height: 15 to 25cm. Flower color: purple to pink. Bloom time: spring. P. stolonifera is easily grown in a shaded garden. There are a number of cultivars on the market.
     'Ariane' is a commercial renaming of 'Bruce's White.'
     'Blue Ridge' has lavender-blue flowers.
     'Bruce's White' is a tall, vigorous selection with sweet-scented white flowers. This started out as 'Shinn's White' and has also been sold under the name 'Ariane,' but 'Bruce's White' seems best.
     'Fran's Purple' - This is a small plant (15cm) with purple flowers from the garden of Fran Lubera in Connecticut. I bought this at a NARGS plant sale in 1987 and introduced it in my retail catalog.
     'Home Fires' has warm dark pink flowers.
     'Irridescens' has pearly lavender flowers.
     'Wister's Pink' is a large selection with light pink flowers.
     'Pink Ridge' has medium-pink flowers. This is similar to the usual wild forms here in Fayette Co., PA.
     'Sherwood Purple' is large than 'Fran's Purple' and has similar purple flowers .

Hybrids - P. adsurgens and P. stolonifera will cross with each other. In 1987 I saw a P. adsurgens × P. stolonifera cross that Lincoln Foster had made growing in the garden at Millstream, and I made one myself about 1991. These were both trailing plants with pink flowers. Mine was not very vigorous and did not last more than a year. The Foster plant was apparently not worth introduction either.
     P. ×procumbens is a name applied to the hybrid between P. subulata and P. stolonifera. This apparently has been found in nature. There are a few cultivars available. These make loose mats and are 15 to 20cm tall.
     'Millstream' is a vigorous clone with large pink flowers.
     'OGK' was found in Lee Raden's garden in Phoenixville, PA. The name means "Only God Knows," referring to its origin.
     'Pink Profusion' is a new selection bred by Jim Ault at the Chicago Botanic Garden and not yet introduced. It is described as 8" tall in bloom and having relatively large purple-pink flowers with a white eye.
     'Variegata' has white-margined leaves and pink-purple flowers.
     'Snowflake' and 'Viola' were plants introduced by The Primrose Path in the early 1990s but probably are not now available.
     P. adsurgens will also cross with moss phloxes, at least with P. nivalis. 'Sunrise' is a P. nivalis × P. adsurgens hybrid I introduced in 1990. It has wide needle foliage and flowers of the peach-pink shade of the P. adsurgens parent. This is often available from Mt. Tahoma Nursery.
Phlox stolonifera in the wild, Fayette Co., PA
Phlox stolonifera 'Bruce's Whie'
Phlox 'Sunrise' Phlox stolonifera 'Wister's Pink' Phlox ×procumbens 'Snowflake'
Buckleyi Group
Phlox buckleyi (Sword-leaf phlox) - Range: Virginia and West Virginia in areas of shale barrens. Habitat: open woods and barrens margins. Height: 15 to 45cm. Flower color: purple to pink. Bloom time: early summer. This does not seem to be commercially available. All the plants I have seen sold under this name have been P. glaberrima ssp. triflora.

Phlox cluteana - Range: along Utah-Arizona border. Habitat: Open pine woods, 6000 to 10,400ft. Height: 15 to 20cm. Flower color: purple. Bloom time: early summer. This is not in cultivation.

 Phlox stolonifera × adsurgens
Speciosa Group
All of these are western species that are more or less erect (in the range of 15 to 30cm) rather than prostrate and mossy. None of them is familiar in horticulture and all are difficult to nearly impossible to cultivate in the eastern US. For this reason I have little personal knowledge of them and am not going to give them much space. Ranges and taxonomy can be seen at http://plants.usda.gov/. A number of these species are available as seed from Alplains. This is a group that western gardeners should try since many of them are very beautiful. I saw P. mesoleuca in bloom in Bob Heapes' garden in Colorado in 1993 and was very envious. P. longifolia ssp. brevifolia (listed as P. grayi by Alplains) lasted a couple of years and bloomed for me in southwestern PA. Given careful siting and protection from winter wet it might do fairly well in parts of the East.

Phlox amabilis
Phlox caryophylla
Phlox colubrina
Phlox dolichantha
Phlox hirsuta
Phlox longifolia
     ssp. brevifolia - Range: Utah, Nevada, Arizona, eastern California. Habitat: dry, rocky slopes. Height: 8 to 15cm. Flower color: purple to pink. Bloom time: spring. This has foliage similar to that of P. pilosa. The plants I grew from Alplains seed had flowers of a nice clear pink.
Phlox mesoleuca
Phlox mexicana
Phlox nana
Phlox oklahomensis
Phlox roemeriana
Phlox speciosa
Phlox stansburyi
Phlox tenuifolia
Phlox triovulata
Phlox viridis
Phlox viscida                                                                                (next page - Moss phlox)
Phlox longifolia ssp brevifolia in a Fayette Co., PA garden

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