Dahlias are originally from Mexico so managing the heat shouldn’t come as a surprise. Nonetheless, I’ve been marvelling at their cheery resilience and wave after wave of flower, even when the foliage has been crisped by a rogue heatwave. I’m currently growing an unnamed single yellow and a bold red, rescued a few years ago in a Bunnings seedling tray, and my plan this year is to add some more.
I like the simplicity and openness of the single flower-types, as does the great New Zealand plant breeder Dr Keith Hammett. He’s been working on dahlias since 1989 when he visited Mexico and saw them growing in the wild. Hammett was impressed by their diversity of foliage colour and flower form and he’s been been having fun ever since with what dahlias can do.
Sonja Cameron at Planters Patch Nursery has two favourites among the Keith Hammett dahlias she sells: “Home Run” has burgundy foliage and a cerise flower “in spectacular numbers”; and “Titoki Point” is like a tropical sunset, with lemon bleeding into peachy-pink. Both are bushy plants to a bit under a metre, are resistant to the powdery mildew that can affect dahlias in Sydney’s muggy late-summer, don’t need to be staked and bloom from November until past Mother’s Day. They are easy to use in the garden and in pots.
The bigger-flowered dahlias, such as the florist’s darling “Cafe au lait”, take a bit more work. They grow to head height and need stakes or a trellis to lean against and help hold up those heavy heads. Set up the supports before planting the tubers, to avoid piercing the tuber with the stake. Once they have four or five sets of leaves, pinch out the growing tip to encourage branching for more flowers and a more compact plant.
Dahlias can be left in the ground over winter, though they risk rotting if the weather’s wet. The smaller types can be left for several years before being dug and divided, though the bigger tubers grow best if best dug and divided annually.
Dahlia tubers are generally ordered in winter and planted out in spring, though the really serious growers wait until December to avoid having blooms spoiled by hot summer sun. So it’s late in the day, but still possible to get some dahlias into your garden right now. Planter’s Patch will have flowering dahlias at Collectors’ Plant Fair and Tim Drewitt from Red Earth Bulbs in Victoria plans to bring 40-50 different dahlias to Collectors’. As well as Dinner Plates dahlias, with multi-petalled blooms bigger than a baby’s head, Drewitt will have smaller growers, including the Anemone Dahlias, which look like mini-peonies. They’ll be “starter” plants, which Drewitt says are likely to bloom before the season is finished.