February 2005

A State of Phlox By Rick Schoellhorn, University of Florida

With the advent of the Intensia phlox series a few years ago, the entire genus of phlox and its varied species are seeing resurgence in popularity, which is a great thing as this genus of plants is really pretty amazing. Most of the major breeding firms are putting out new releases, and it is nice to see this plant recycled and improved.

There are three major types of phlox in commercial production, and each group has a different niche that it fills at retail. All phlox groups are native to the North American continent, so they can offer additional sales if marketed as native plants. The original germplasm came from the United States and was brought back to Europe, where extensive breeding brought most of the early color forms. I’m not sure if you can still be considered a native when you went off to Europe for 100 years, but don’t get me started…

I wanted to take a look at some phlox groups — what is new, what has been around and what is coming back. And, we’ll discuss Phlox subulata in a future article.

Phlox drummondii

Let’s start with the Phlox drummondii types; these are the only group of true annuals in the genus. The obvious improvements are the vegetative lines coming from Suntory and Proven Winners. Compared to the traditional seed forms the Intensia (PW) and Astoria (Suntory) lines are more mounding, vigorous and continuous flowering under our trial conditions. Cuttings are in bloom when the trays arrive and remain in bloom pretty much continually in both summer and winter (Intensia only) trials. For Southern use, these vegetatively propagated plants are practically year-round color, while seed types are basically a spring item with little heat or humidity tolerance. Also, these vegetative lines continue to flower through the winter, while seed types rosette in early season and only come into bloom as temperatures warm in spring. In my opinion, the Intensia and Astoria series are the best new crop we’ve trialed in the four years we’ve been doing this. Great seasonal tolerance and continuous color.

This is not to say that there aren’t some incredible seed types out there. PanAmerican Seed’s 21st Century is an excellent red, white and blue series that has strong color potential for spring use in the South and into summer in the North. Additionally, in researching what is actually available in the seed market, I found many designer color blends that I really think are awesome and rarely seen. I think the ‘Tapestry Mix’ of antique shades, including burgundy and blue tones, is stunning; ‘African Sunset’, ‘Crème Brule’ and ‘Coral Reef’ are also good designer blends of apricot, salmon and yellow tones. With this much diversity in genetics, I suggest growers try to tap into the same market that is driving the sales of calibrachoa and other spring flowers: terra cotta.

Phlox paniculata

Phlox paniculata types are the old-fashioned perennial or garden phlox with an upright to mounding habit. These are usually sold as rooted cuttings or divisions and have a great Northern but a limited Southern market. That is changing with the release of two new series from Ball FloraPlant and Anthony Tesselaar. Ball’s Flame series is in our winter trials this year and just went through 26° F with no loss of flowers or damage. Tesselaar’s Volcano series has also been in our trials, and while summer temperatures really beat up the plants, they flowered in fall and are still flowering in the trial landscape area. There are hundreds of P. paniculata cultivars out there, and breeding has traditionally been to improve powdery mildew resistance, which has been fairly successful. The newer breeding, though, is aimed at free flowering on smaller plants, which will enable nurseries to sell P. paniculata with traditional spring crops and avoid the problem of older varieties flowering later in summer when sales are not so strong. So far, both new releases look very good, and I like the color distribution in the Volcano series — lots of contrast and good strong eyes.

Another group worth looking into is the variegated foliage types. For those of us in the South, these may make excellent winter container color; for the North they are an additional price point. ‘Becky Towe’, a new variety from Plant Haven, has variegated foliage and reddish new growth. There are some older cultivars that are still very nice, such as ‘Harlequin’, which has deep pink flowers and foliage with a broad white edge and a green center. Hallson Gardens carries ‘Rubymine’ a cultivar with intense tricolor pink foliage and medium pink flowers, as well as ‘Crème de Menthe’, an old-fashioned, larger type with good variegation and pale pink flowers with a deep pink eye. The new breeding is only now hitting the market, so I look forward to a lot of new improvements and a revamping of this old garden standard.

Others

There is an emerging market of other species that will really expand the territory of phlox use. Phlox divaricata is a good place to start. Fully hardy South to USDA Zone 10 and northwards to Michigan and Minnesota, this plant has a lot of great potential and a strong fragrance in some cultivars. We see some powdery mildew on bad years here, but it is essentially a trouble-free perennial, and the flowers vary from a beautiful fusion of deep blue to violet, and there are now cultivars of white, blue, purple and pink tones as well. Other less common species include P. pilosa, P. maculata and P. arendsii; all these species tend to the blue to pink range but offer intermediate heights, taller than most seed selections but not as large as P. paniculata.

Like all groups of plants on the market the main stream hardly ever offers the diversity of what is out there genetically. That’s good, as it means we always have a stream of new crops coming into the market. Phlox is about to bloom (sorry), and I think it will bring this genus of plants into the limelight in a big way. I think the major developments are in breeding of the P. drummondii types for perennial qualities and extended season of flower, but our industry’s plant breeders are capable of such amazing transformations, who knows where we will end up.