A short stay in Paris in September allowed me to pay a visit to an old friend of mine who works as chief gardener for the bonsai collection of the city of Paris. This collection is set in the Parc Floral de Vincennes, a large place which acts as urban park and botanical garden and spread on 31 hectares wide. As the weather was nicely warm we took a stroll around the park and my friend insisted in showing me the dahlia collection, after we of course dutifully inspected the bonsai and shared tips and advice.
I am not particularly fond of this flower, which brings to me memories of small suburban gardens with Aucuba japonica hedges, garden gnomes and neatly trimmed lawn with painted tire planters. But when we reached the area where the dahlias are grown I could not keep this memory any longer and had to surrender! An amazing sea of moving colors and shapes was awaiting, embellished by sun rays dropping from the large pine trees around, the sweet breeze combined with the blackbirds and robins songs made the whole show stunning.
Now, this is not your usual backyard; the Parc Floral is host for an International Dahlia Show, which means that over 400 varieties are waiting for the visitors between mid-august and mid-September each year. Out of those, 134 were entering the competition this year (note that besides this already impressive cultivars collection there are 57,000 registered cultivars in the world!). And variety is not a weak word here! Colors go from pure white to an almost very deep purple on the verge of blackness, offering every possible shades in-between: yellow, orange, pink, red, purple, with an incredible range of subtle variations within each color and some cultivars are two-colored or even three-colored. Besides the shades, flowers offer a large array of texture and surface state - they can be shiny, dull, or velvety like middle-ages tapestry. Gardeners here have an obvious taste and managed to plant the collection with connoisseur's taste, arranging flower heights and colors so that no one would hide its neighbor and giving an undulating effect which makes like colored waves. 2015 is the 20th international dahlias competition held in the Parc Floral so this is a serious endeavor here. My friend was rather amused to witness my complete change of attitude towards this flower and the frenetic use I was making of my camera.
But let's calm down a little and study the plant from a more scientific than emotional point of view...Dahlia pinnata belongs to the large Asteraceae botanical family (think of asters, daisies, sun-flowers and the like), the Dahlia genera comprises between 40 and 50 other species. D. pinnata, often referred to as "garden dahlia" originates from Mexico where it was both grown and gathered as food by the Aztecs. Its use for human consumption never took hold in Europe; it was largely supplanted by its rival the potato. However, we should note that it was taken as national flower by Mexico in 1963. Another use made by ancient populations of Mexico was as water pipes (the stems are hollow) thus its vernacular names of water cane. It is an herbaceous perennial which produces tubers (the edible part). The name Dahlia was given to this plant so as to honor Anders Dahl who was an 18th century Swedish botanist.
The first hybrids were released in 1806 and the popularity of the plant became increasingly large, it was even boosted when Dahlia juarezii (Devil's or cactus dahlia with long spiky ligules) was introduced. Since then the many professionals as well as keen enthusiasts have considerably contributed to widen the range of available different garden dahlias. Those are named Dahlia x hortensis or Dahlia x cultorum as they are hybrids. The plant thrives in climate zone 7 but does not stand temperatures below zero Celsius and therefore has to be dug and overwintered in a frost-free room. It will offer a great profusion of flowers between July and November in the Northern part of temperate zones. As it can reach between twenty cm (close to a foot) and two meters high (nine feet) it allows gardener to make profuse garden landscaping, from background to foreground. It will grow in full sun, preferably in neutral pH loose fertile soil (what else would a plant ask for?) with good watering though watering should not be done before the first leaves start showing as over watering the tubers might result in damaging them. As stated previously the stems are hollow hence rather weak so props or stakes will be needed. The usual enemies are at stake and should be watched for an fought if need be: slugs, aphids, pathogenic fungi and bacteria. An excessive amount of nitrogen may easily lead to botrytis blight so do not be too generous with this element! If you wish to adorn your home with cut dahlia flowers it is better to cut them in early morning or at sunset when the air is cooler, once the flowers in a vase sugar should be added to the water and the end stems cut back daily, this will help keep the flowers up to ten days.
If you start changing your feelings towards the dahlia flower as I did recently and become more contemplative you will soon understand more easily famous art pieces such as a 'vase of dahlia' by Claude Monet or simply 'Dahlias' by Pierre-Auguste Renoir, certainly not the last of impressionist painters! So as we walk away from this show let us keep in mind the large and fragile diversity of my "suburban garden" flower!