Plant of the Month July 2018: Phlox paniculata

Phlox paniculata are often regarded as a quintessential English garden plant, with their soft, open heads of lightly scented flowers. However, P. paniculata is a native of North America. It was introduced to England by the Quaker botanist John Bartram (1699-1777) of Philadelphia. Phlox is the Greek for flame.

Phlox are a genus of the Polemoniacaea family, native to the eastern and central United States and eastern Canada. Phlox are a large genus of 67 species of mostly perennials with a few annuals and shrubs. The species classed as ‘border Phlox’ include P. paniculata and P. maculata, which are from riverside habitats and produce large corymbs of flowers (a flower cluster whose lower stalks are proportionally longer so that the flowers form a flat or slightly convex head, and in which the outer flowers open first) in midsummer, with oval or lance-shaped leaves. For more information on the different kinds of inflorescence click here  for the RHS School Gardening Spotter Guide. 

The first serious phlox breeder was Wilhelm Pfitzer who introduced P. paniculata ‘Europa’ in 1910. Early hybridisation of P. paniculata took place mostly in France; Victor Lemoine was a well-known French plantsman who introduced a number of cultivars. Two are still listed in the RHS plant finder: P. paniculata ‘Iris’ (1890) and P. paniculata ‘Eclaireur’ (1892).

George Arends was basically a hybridiser and experimented with crossing P. paniculata with other species. In 1912 he began producing his first Phlox x arendsii, crossing the early flowering P. paniculata with the low-growing woodland P. divaricata, the result being a more compact plant which retained the impressive flowering of P. paniculata. Among his first were P. x arendsii ‘Helene’, named for his wife. Although most of these early hybrids have since been superseded, the name x arendsii is still conferred to plants of the same parent species. The original hybrid bred in the 1920s is available today as P. x arendsii ‘Anya,’ which has magenta pink flowers. His great granddaughter, Anja Maubach still runs the nursery he established in the 1930’s.

Phlox became popular in the UK in the 1880’s, when they were bred as a cut flower. They became popular for garden use in late Victorian and Edwardian gardens and were a great favourite of Gertrude Jekyll. By 1917 there were 584 named selections. H J Jones was a pioneering Phlox breeder in the UK in the early 1900’s. He bred a number of cultivars which are still available today, including P. paniculata ‘A.E. Amos’ (1924) with deep raspberry-red eyed bright red flowers which fade in sun and P. paniculata ‘Mrs A.E. Jeans’ (1922) which has pink flowers with a darker eye.

New Dutch selections include P. x arendsii ‘Luc’s Lilac’ and the Spring Pearl Series (‘Miss Jill’, ‘Miss Karen’, ‘Miss Margie’ and ‘Miss Mary’), named for the office staff at the De Vroomen company, and with white, dark pink, lilac-blue, and rosy-red flowers, respectively.

Between the 1930’s and the 1960’s, Karl Foester, a prominent German plant breeder, introduced a number of cultivars which are still available today. In 1934 he introduced the salmon-pink P. paniculata ‘Eva Foerster’ AGM. In the 1940’s he introduced the lavender P. paniculata ‘Amethyst’ (1940) and P. paniculata ‘Schneerausch’ (1949) which has big thick creamy white flowers from shadowy slate lilac buds. In the 1950’s he introduced the pale pink P. paniculata ‘Rosa Pastell’ AGM (1951), P. paniculata ‘Prospero’ AGM (1956) with fragrant, white-eyed, light lilac-purple flowers with pale-edged petals, and P. paniculata ‘Violetta Gloriosa’ (1956) with pale lilac flowers and a large white centre. One of his last introductions in 1964 was the purple P. paniculata ‘Dusterlohe’ (synonym ‘Nicky’).

Karl Foester is reputed to have delivered the memorable judgement that ‘a garden without phlox is not only a sheer mistake but a sin against summer.’

Karl Foerster developed the concept of ‘wilderness garden art’ in his garden in Potsdam-Bornim which is a short train ride from Berlin. Click here to read more about his garden.

Bonne Ruys founded the Moerheim Nursery in the east of the Netherlands in 1888, specialising in perennials. The business became the most notable nursery in Europe for perennials in the first half of the twentieth century. In 1937, he bred Ppaniculata ‘Frau Alfred von Mauthner’ (synonym Ppaniculata ‘Spitfire’) which has brilliant cherry-red flowers, and leaves that have a dark red tinge to them. Other cultivars available today include Ppaniculata ‘Wilhelm Kesselring’ (1923) with blue-lilac flowers with pale cream blazing, and a hint of red-magenta in the eye, and Ppaniculata ‘Caroline van den Berg’ (1927) with lavender flowers with a deeper eye. (Ppaniculata ‘Caroline van den Berg’ was an HPS conservation plant in 2008.) Ruys also introduced two white cultivars, Ppaniculata ‘Rembrant’ (1900) and Ppaniculata ‘Mia Ruys’ (1922). Ppaniculata ‘Milly van Hoboken’ (1922) has delicate pink flowers.

His daughter, Wilhelmina Jacoba Moussault-Ruys was a Dutch landscape and garden architect. Her gardening legacy is maintained in the Dutch town of Dedemsvaart, home of the Tuinen Mien Ruys, which contains 30 inspirational gardens. Along with Piet Oudolf, she is considered to be a leader in the ‘New Perennial Movement.’ Click here for a link to the gardens.

There has been a long tradition of breeding Phlox cultivars in Russia. P. paniculata ‘Uspekh’ AGM (synonym ‘Laura’) was bred by P. Gaganov in 1937.

The high point of phlox breeding in this country occurred after WW II when a local grower from Otley, Fred Simpson and Capt. Bertram Symons-Jeune of Windsor began serious efforts to produce modern varieties for British gardens and many of their cultivars are still available today.

In 1913, Fred Simpson, started a poultry business developing quality strains of hens on what is now the site of Steven Smith’s Garden Centre in Otley. Twenty-one years later as his health failed, he turned his attention to horticulture and he developed an interest in breeding better strains of perennial plants. These included the world-famous Otley Korean Chrysanthemums and the Lupin ‘Otley Yellow’, but it was his work with herbaceous Phlox paniculata which was most successful. He introduced the regal strain which included cultivars named after royal residences, including P. paniculata ‘Windsor’ which has bright salmon pink flowers with cerise-pink eyes, and P. paniculata ‘Sandringham’ which has cyclamen pink flowers with dark eyes. Courtyard Planters in Otley propagate several of Fred Simpson’s cultivars on behalf of ‘Otley in Bloom’. P. paniculata ‘Otley Choice’ and P. paniculata ‘Otley Purple’ are still listed in the RHS Plant Finder.

Captain Bertram Hanmer Bunbury (B.H.B.) Symons-Jeune, was a notable rock gardener, designer, and breeder of phlox, selected mostly for flower size and colour, and for vigour. Between 1940 and 1960 he supplied ten varieties per year to James Baker’s Boningale Nursery near Wolverhampton, which is now a wholesale nursery. They include P. paniculata ’Eventide’ (1947) has mauve-purple, scented flowers. Other cultivars include P. paniculata ‘Vintage Wine’ (1957), a dark leaved variety with royal purple-red flowers; P. paniculata ‘Othello’ (1959) which has large heads of claret-red flowers with a light fragrance; its shoots and leaves are dark green flushed with purple. Another cultivar is the highly fragrant P. paniculata ‘Bright Eyes’ (1967) which has very fragrant crimson-eyed, white-pink flowers.

Alan Bloom (1906 – 2005) developed his nursery in the grounds of Bressingham Hall. Perennials were historically grown in deep borders against a wall or fence, as favoured by the gardening stalwarts William Robinson and Gertrude Jekyll. Plants struggle to grow in the part shade, become leggy and require staking. Alan Bloom started to grow perennials in island beds and noticed that they were sturdier as a result, and that the weeding of the beds was also easier! Influenced by Karl Foester, he developed a number of Phlox cultivars including P. paniculata ‘Mother of Pearl’ AGM (1954), with slightly cupped white flowers suffused with pink. He also discovered the distinctive P. paniculata ‘Norah Leigh’ AGM (1957), which has variegated white-splashed leaves and soft-pink flowers, growing in Norah Leigh’s Broadwell Manor garden in Gloucestershire, but it is a much older plant having grown in Munich Botanical Garden for more than 80 years. The violet coloured P. paniculata ‘Franz Schubert’ AGM (1980) was one of his last introductions.

In the early 1990’s Piet Oudolf the Dutch plantsman and landscape gardener, produced some lovely blue cultivars, including the lavender-blue P. paniculata ‘Blue Evening’ and the indigo P. paniculata ‘Blue Paradise’, which is one of the earliest of the phlox to flower; the quality of its blue colour changes throughout the day, at dawn and dusk it is a magical watery blue, and then at midday, it is almost pink. Another Dutchman, Coen Jansen bred P. paniculata ‘Utopia’ in the 1990’s.

The pale pink P. paniculata ‘Monica Lynden-Bell’ AGM (1970) was found as a seedling in Lynden-Bell’s Hampshire garden and popularised by Bob Brown of Cotswold Garden Flowers.

P. paniculata ‘David’ is a recent American introduction. This was found as a chance seedling close to the Brandywine River Museum, in Pennsylvania in 1991, and developed for the florist trade. It is tall, healthy and late-flowering, replacing in many ways the old stalwart, P. paniculata ‘Mt. Fuji’, long considered to be the best white phlox.

By the 1970’s, interest in growing Phlox paniculata appeared to wane. There was a perception that they were difficult to grow and suffered from disease including the dual problems of mildew and eelworm, which can disfigure phlox plants.  Mildew can be controlled by good air round the plants and consistent moisture in the soil, maintained by mulching around the roots.  Newer cultivars are bred for mildew resistance. Eelworm, although incurable, is much less prevalent that historically because nursery stock has been cleaned up and resistant new varieties introduced. When it does strike, the stems of the affected plants should be destroyed and replaced with new plants propagated from root cuttings (the roots do not host the pest).  Phlox can be divided in autumn or spring. Many Phlox are grown as containerised plants which should be planted out as soon as possible as they are not particularly happy in pots.

Over the intervening years when interest in phlox dropped off, many cultivars remained in gardens, but the names of many were gradually forgotten, and many varieties lost all together.  The great gardener and writer, Christopher Lloyd, once wrote that he wished to get the real names for some of the old-fashioned stalwarts including his P. paniculata‘Doghouse Pink’ (from Doghouse Farm, on Stone Street, Canterbury, originally a pub, The Dog). He described it as being full of charm with its two shades of soft pink. He also described a ‘Long Border Mauve’ which grew in the Dixter Long Border since before he was born, which has a penetrating colour that shows brilliantly from a distance.

Today Dutch, German and Russian nurserymen continue to produce excellent new plants. The newer introductions include the pink and white P. paniculata ‘Peppermint Twist’,

and the delicate pink and yellow P. paniculata ‘Sherbert Cocktail’. Phlox should usually be regarded as a mid-border plant, as even well-grown specimens often lose their lower leaves by the time they flower.  The exceptions to this rule are some of the new strains of dwarf phlox being developed in Holland for pot or front of border use.  One such group is the Flame Phlox series, which includes an endless selection of colour choices on compact, well-flowering plants.

The RHS undertook a trial of Phlox between 2011 and 2013. It is interesting to read the report and to learn what criteria the plants had to meet to achieve an Award of Garden Merit (AGM). Some species had their AGM rescinded. Click here to read more.

The German plantsman, Hartmut Rieger published a photographic journal ‘A journey through my garden…’ on the internet in 2005 and added to it until his death in 2013. The data for Phlox and Helenium species are based on measurements and observations he made in his garden; he also recorded the original breeder. Click here for the link.

Another interesting link is to a Lithuanian nursery which specialises in Phlox and Day Lilies. There is a gallery of about 1200 Phlox species many of them bred in Russia. The website is in English! Click here for the link.

The National Collection of Phlox paniculata is held by Leeds City Council at Temple Newsam Estate.

Page image: Phlox paniculata ‘Mother of Pearl’ AGM (Image courtesy of HPS image library)

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