Dedicated dahlia enthusiasts regard lifting the tubers as par for the course...
HARD as I've tried over the years, I cannot learn to love dahlias. They're a plant I've been familiar with since childhood. My dad would've grown them and I recall the tubers hung-up, over-wintering in the area beneath the house – what we called the 'understairs' – which served as a basic cellar-cum-den. The names of the varieties, neither he – now 87 years old – or I, can recall but they conformed to what I regard as the dahlia's typical attributes, namely a garish, in-your-face showiness, and floral patterns reminiscent of Strictly Come Dancing viewed through a kaleidoscope after consuming copious amounts of LSD. Individually, the variety of dazzling, intricate patterns breeders have created over generations are truly breathtaking – and they make lovely cut flowers, yet for me are just too ostentatious for the garden.
There is one notable exception to my dahlia aversion – ‘Bishop of Llandaff’ – and this is because it doesn't match the characteristics outlined above, in that it has deep bronze foliage and bright scarlet, single to semi-double flowers. There are other 'Bishops' available, including 'Oxford', 'Canterbury' and 'Auckland' though 'Llandaff', with its Award of Garden Merit (AGM), sets the standard.
To many other gardeners the world over, dahlias are the darlings of late summer and autumn garden, with often saucer-sized blooms that give almost unrivalled bursts of bright colour, whether planted in pots or in the midst of a bed or border. Some are more suited to the former, while others, like the aforementioned 'Bishops', are at home nestled among perennials and shrubs with their roots in terra firma.
However, without exception these Mexican natives always prefer full sun and humus-rich soil. Apart from slugs and snails, these perennials are surprisingly robust when it comes to pests and diseases but to say they are low maintenance would be an exaggeration – a point that conveniently brings me to the dahlia's other drawback.
Dahlias don't like prolonged cold or excessive damp, which means in many circumstances the best option is to lift them in the autumn and store them, as my old man did in the 1970s, somewhere dry and cool. There are many gardeners, especially those in coastal areas, like my friend Bernard Magennis at Rossglass Rose Garden, who will put his faith in Mother Nature and a layer of mulch. Some may even place an upturned pot over the plant to reduce the amount of rain it's exposed to. This is an approach that due to our temperate climate, will probably work around nine times out of 10. But a prolonged cold spell, like the one we experienced in the winter of 2011, is likely to kill the tubers.
If you wish to be on the safe side, lift your dahlia tubers as the leaves blacken with the arrival of the first frosts. Loosen the earth around the plant and lift the tuber carefully in one piece with a fork before cutting the hollow stems down to almost ground level, tying on a label if you have more than one variety. Only pieces with a solid piece of crown and bud will regrow.
Clean off the soil, using a brush if necessary, taking care all the time not to damage the tuber. Leave the tubers in a sheltered spot like a greenhouse or garage to dry off, before removing the last of any earth that's caked on, or damaged or diseased bits. Pack the tubers in a cardboard box or cover them with dry compost before storing them in dry, a frost-free location.
