Grow: The secret world of Dahlias

Judging these colourful flowers is an exacting process; you can see it in action today in Greystones

What does it feel like to have a plant named after you? Someone who knew the answer to that question was the late John Markham, the greatly respected Irish gardener who died earlier this year. He earned that special horticultural honour courtesy of his friend, the Irish dahlia breeder Alick Branigan, who in 2013 formally registered the very lovely, purple-flowering pompon-type Dahlia 'John Markham' as a distinct variety with the RHS, much to the surprise and delight of Markham and his family.

Dahlias, that genus of vividly colourful, tuberous flowering plants which originate in South America, and whose exotically beautiful blooms light up our gardens at this time of year, were one of Markham's great passions.

He was first introduced to the flowers in the 1970s, by a gardening friend, who, noting his prize-winning talent for vegetable growing, handed him a few tubers, telling him that if he could grow good potatoes, then he could almost certainly grow good dahlias. Very soon Markham was growing up to 100 plants in ruler-straight rows in his Greystones garden.

“John always did everything to perfection and spent every available moment that he could tending to his plants. We used to tease him that gardening came first, his family second,” says his widow Mary, who is also a keen gardener.


Not only did he grow wonderful dahlias, but he also regularly exhibited them, and as a National Dahlia Society–approved judge (a title you only earn by first sitting an exam set by the UK-based NDS), he judged them at many of the horticultural shows that typically take place around Dublin each summer.

Growing and staging dahlias to exhibition-standard in what’s known as a horticultural show’s ‘competitive classes’ is no mean feat; not only must the flowers be blemish-free and brilliantly beautiful, but they must conform to certain strict criteria in accordance with their class. Size, shape, symmetry, freshness, the formation and arrangement of the petals, the straightness and thickness of the stem, even the angle at which the flower sits on the stem (no less than 45 degrees) are all factors that are taken into account when it comes to judging, a process guided by a set of strict rules.

Some floral flaws are deemed less forgivable than others. Any sign of limp, drooping florets is, for example, classed as “A very serious fault” according to NDS criteria, while out-of-proportion stems will still lose you points, but – phew – come under the heading of “Faults of a lesser degree”. To make things even more challenging, the dahlia genus is a vast and confusingly varied one, with nine classifications, 42 species and countless named varieties.

Depending on the particular dahlia, its flower can be as small as an old pound coin or as big as a large dinner plate.

Any dahlia flower exhibited in a horticultural show must be the right size for its particular competitive class and correctly named; if not, the exhibit is automatically disqualified. To check the size is correct, the judges use special measuring rings approved by the NDS, which they slip over each flower.

And I do mean ‘slip over’. It must fit cleanly over the dahlia bloom, without so much as the tip of a single petal touching its inner edge.

All of this might make the process sound stuffy, but anyone who has exhibited dahlias at one of the horticultural shows will quickly testify to how rewarding it is. "For John, as for most people, the big joy wasn't in winning, but in taking part," says Mary. If you'd like to see the judging process in action, then I suggest paying a visit to the Delgany & District Horticultural Society's annual Dahlia Show, which takes place today.

Along with his many other talents, John Markham was a stalwart member of the society for more than 40 years, as well as its hardworking chairman from 1995 until shortly before his death.

Dahlia 'John Markham' can be seen growing in the dahlia beds at Arás an Uachtaráin. These were designed by the Dublin floral designer Christopher White (winner of a silver-gilt medal at this year's Chelsea Flower Show) a couple of years ago, at the special request of President Higgins. Tours of the gardens, which are home to a number of Irish-bred dahlia varieties, are given to the public each Saturday (call the Phoenix Park Visitor's Centre at 01-6770095 for details) .

As well as planting it on his grave this summer, John’s widow also continues to grow the dahlia named in his honour in their Greystones garden, where it’s flourishing. “I’m growing it in the front garden alongside the well-known dark-leaved, scarlet-flowered dahlia, ‘Bishop of Llandaff’. I like to tell people that John’s mixing with high society.”

The Delgany & District Horticultural Society's Dahlia Show takes place today at St Patrick's Primary School, Church Road, Greystones, Co Wicklow, 3pm-5pm