Dahlias: the old-fashioned flowers that are suddenly back in fashion

After several decades of being sneered at as a bit naff, dahlias suddenly in vogue.

Gorgeous: ‘Cafe au Lait’ dahlias. Picture: Alamy

It is the season of the dahlia. In late summer to early autumn, these colourful and flamboyant blooms strut their stuff in most southern parts of Australia. And after several decades of being sneered at as a bit naff, dahlias are back in fashion.

In the UK, the trend has grown over the past 10 years to the point where dahlias are florists’ favourites for high-end events and society brides. The softer shades of new varieties such as ‘Café au Lait’ are taking over from the traditional sizzling (some say garish) dahlia colours, substituting for romantic peonies and full-petalled roses in floral work and garden beds.

In Australia, esteemed garden photographer Simon Griffiths confirms dahlias’ rise and rise. “I know lots of gardeners who are adding dahlias – they’re rewarding to grow and multiply quickly so you soon have a large bed of them.” In Griffiths’ Victorian garden, which has featured in this column, he admits to “a weakness for red dahlias” but has added ‘Café au Lait’ this year. “It has huge heads of the most amazing milky colour,” he says.

Dahlias en masse. Picture: Simon Griffiths

The dahlia world is complex. There are 42 species and thousands of hybrids and cultivars in almost every colour except blue. They are classified into numerous groups, based mainly on their flower size and shape. Dinner-plate dahlias are the most spectacular, with flower heads that can be 30cm across; they’re tall plants (up to 2m) that need to be staked, as are the cactus group, named for the way the sides of the petals roll under so they look spiky. Anemone or collarette types have ruffled centres with an outer ring of flat petals, while the waterlilies and pompoms are self-explanatory. Go to a dahlia show (many are held in March and are listed at dahliasaustralia.org.au) and you’ll be amazed at the variety. Competition is fierce.

Gardeners with a more casual style have embraced the dwarf and dark-foliage dahlias that are small, bushy and don’t require staking. Most have small, simple flowers with a single row of brightly coloured petals. When the foliage is dark bronze to purple, the contrast to flower colour is especially good, such as in the ever-popular ‘Bishop of Llandaff’ with its red flowers and purple-black foliage.

Dahlias are a diverse bunch. Picture: Simon Griffiths

Dahlias are in the daisy family and originally from Mexico, where they are the national flower. The Aztecs bred and cultivated them for food (the tubers are potato-like) and medicine; they arrived in Europe in the 1700s and the Impressionist painters helped popularise them from the 1860s.

They prefer a cooler climate without heavy frosts, a sunny, sheltered spot and free-draining, fertile soil. Plant the fleshy tubers (available by mail order and in nurseries) in spring after the frosts – they’ll take about eight weeks to flower. They’re thirsty, greedy plants that respond to lashings of soluble fertiliser and seaweed extract. If your soil is wet or frozen in winter, lift the tubers after the stems die down. Propagate dahlias by dividing tuber clumps, or from cuttings or seed.

To see dahlias growing and flowering, take a drive in March or April to visit specialists such as Country Dahlias at Winchelsea, Victoria; Winkie Dahlias in South Australia’s Riverland; or Van Diemen Quality Bulbs in Tasmania. You’ll also find display beds at the Blue Mountains Botanic Garden at Mt Tomah and Adelaide Botanic Gardens.

Q&A

How often should I fertilise my lawn? Amanda Haynes, by email

For warm season grasses such as couch, kikuyu, zoysia and the buffalo varieties, fertilise in late September as growth begins, again in January if there is rain, and in April, to strengthen the lawn going into winter dormancy. Cool-season grasses such as tall fescue, bent and ryegrass, grown only in cold regions, keep growing in ­winter and are best fed in early autumn.

I’ve had trouble growing anything under my neighbour’s row of 50-year-old pine trees. Can you suggest any natives or ways to help plants survive? Dave, Sydney

Pine trees exhibit allelopathy, the process by which chemicals exuded from roots and leaves suppress the growth of surrounding plants. The needles make the soil acidic and can form a blanket, so removing them regularly can help. Add lime to counteract acidity. There’s also strong competition for water, nutrients and light. Some native suggestions are birds nest fern, Correa alba and groundcover Cissus antarctica. Tough exotic survivors are clivias, walking iris (Neomarica), Dicliptera sericea and many ­bromeliads and succulents.

I’m battling an increasing number of suckers coming up in the lawn and gardens from my weeping cherry tree. Why the increase and how do I safely remove them? Darren Dent, Canberra

Suckers come from the vigorous rootstocks onto which the desirable varieties are grafted, so must be removed or they’ll take over. Cut or pull them off below soil level; an organic, non-systemic herbicide like Slasher would burn them. Increased suckering might indicate stress on the weeping cherry or widespread root damage or disturbance.