Dahlias are invaluable summer flowering plants for brightening up borders, patio containers or as cut flowers. Singles, doubles, small and dainty or huge ‘dinner plate’ forms, in almost every colour and shade possible.
Dahlias are a fairly recent introduction to Britain. Native mostly to Mexico and grown by the Aztecs as a food crop – although this use practically died out after the Spanish Conquest when more palatable alternatives were introduced!
It is thought Dahlias were originally brought to Europe by the Spanish Invaders, thinking the tubers may be a useful food crop – an alternative to the potato. They never gained popularity; one description is of them having a “repulsive, nauseous peppery taste which inspires equal disgust to man and beast”.
Dahlias are bushy herbaceous perennial plants which overwinter as swollen root tubers (potatoes which are stem tubers – the ‘eyes’ being the stem nodes). They are generally classed as tender in this country, meaning they will not stand frosts. However, some cultivars are hardier than others, with many now surviving our winters – particularly in sheltered gardens or if covered with a protective mulch, such as bracken. But growing from a tuber, a large stored food source, enables them to grow really quickly in late spring and early summer once the weather is warm enough. They will then reward with blooms all summer long, often well into the autumn, until one sharp frost blackens them, and finishes the display for the year.
Dahlias are members of the Asteraceae family – the ‘Daisies’. Yes, related to our lawn daisies and dandelions, Michalemas daisies, Sunflowers – and another popular ‘hobby’ or ‘exhibition’ flower, the Chrysanthemum. Although there are only 42 species of Dahlia, there are now thousands of hybrids or cultivars, singles and doubles, and forms including pompoms, decorative, spider, water-lily, collarette, anemone, orchid and peony types.
This great variety results from Dahlias being octaploids – that is, they have eight sets of chromosomes. Whereas most plants (like us) are diploids – with just two sets – one from mum and one from dad. So the permutations of what the offspring from seed can inherit is far greater – and they may look unlike either parent!
However fancy and colourful, very few have the benefit of scent – and a true blue has also still evaded all breeding programmes.
In Eastern Europe they are known as ‘georginas’ after the botanist Johann Georgi of Petersburg who was involved in some of the early breeding of hybrids. However these summer wonders were officially named after Dr Anders Dahl, a Swedish botanist and pupil of Linnaeus. Behold the Dahlia.
• Manea School of Gardening, a Royal Horticultural Society Approved Centre, has a range of RHS Courses at all levels comm+encing in September.
For more information visit: www.maneaschoolofgardening.com or contact Mary via email at: firstname.lastname@example.org