Dazzled by dahlias

Sunday, 28 February 2016

Dahlias in the garden of Sandra Wilson in Sydney

I find it hard to believe it now, but I once hated dahlias! I regarded them as rather uncouth and the province of deranged gardeners who only wanted to see how big they could grow the flowers in order to win a competition. I never imagined that one day they would be amongst the stars of my summer garden. The turnaround is mainly due to my evolution from wanting to grow traditional English border plants to an appreciation of how warm-climate plants are far more suited to our hot, humid Sydney summers, which proved anathema to the delicate Northern Hemisphere perennials I once delighted in. Dahlias are also in fashion in UK gardens now, thanks to the enthusiasm of gardeners such as the late Christopher Lloyd, who used them with other exotic plants to create brilliant and exuberant borders.

Tall dahlias in the garden of Sandra Wilson in Sydney

I haven't (yet) embraced dinner plate-sized show dahlias, which just don't blend in easily with most other plants, but the smaller-flowered ones form telling clumps in my garden and provide colour over many months: from November to May, but looking particularly good right now. Tuberous perennials of the daisy family (Asteraceae) from Mexico and Central America, they are perfectly at home in Sydney. Few other plants can match them for flower power! Last week I visited the garden of a friend, Sandra Wilson, who lives not far from me, and was overwhelmed by the number of dahlias she had growing, varying from low-growers only 30 cm in height to others that towered over my head. The hues of the petals range from crisp white through various shades of pink and cerise to deep reds, yellows and oranges, the latter hues being wonderful for 'hot-coloured' borders; a number of the flowers have two or more colours in the petals, combined as if in a watercolour painting.

Waterlily-flowered dahlia in the garden of Sandra Wilson in Sydney

Whilst many of the blooms are of single form, others in the garden are of the 'cactus', 'waterlily' or 'collarette' types, underlining the mindboggling diversity of dahlias. The blooms mingle in glorious profusion with the many other flowers of late summer in her garden: such as roses, Salvia, Geranium 'Rozanne', perennial Aster, Pentas, early Plectranthus varieties, Tibouchina and Justicia species. The tallest of the dahlias jostle good-naturedly with some lofty self-sown Zinnia flowers, fellow members of the daisy family, which provide a similarly long period of summer colour.

Dark-leaved dahlias in the garden of Sandra Wilson in Sydney

In recent years, many gorgeous new cultivars have become available in nurseries, including some with alluring dark foliage. The classic 'Bishop of Llandafff' (which was a chance self-sown seedling named in the 1920s by Cardiff nurseryman Fred Treseder) with its stunning red flowers was one of the first of these. I was amazed to learn that lots of the lovely ones in Sandra's garden were also self-sown seedlings, descendents of her original plantings from years ago. It certainly pays to keep an eye out for chance seedlings in the garden.

Two-toned dahlia in the garden of Sandra Wilson in Sydney

Dahlias like a sunny position in the garden, with rich, moist (but well-drained) soil. They'll appreciate organic matter dug into the soil at planting time; and a fertiliser applied in spring will help them grow vigorously. Occasional feeds of a water-soluble tomato fertiliser during the growing season promote flowering; as does conscientious removal of all the spent flowers. I find it quite therapeutic to snip these off every few days, and it makes a big difference to the appearance of the plants as well! If you'd like some seedlings, leave a few deadheads on towards the end of the flowering period in autumn. Tall-growing forms require support: I use metal cradle stakes, but canes can be used and the plants tied to them with twine. Pinching the growing tips back early on in the season helps develop a stockier plant.

Self-sown dahlia in the garden of Sandra Wilson in Sydney

Sandra leaves the tubers in the ground over winter, a practice which generally works well in Sydney, as we don't experience the severe cold that necessitates the nuisance of digging them up and storing them over winter that is required in cooler climates. Whilst they are dormant, there is a gap in the garden; however, in Sandra's garden self-sown spring annuals such as poppies colonise these areas to provide a pretty display. In my own garden, I have taken to sowing seeds of shallow-rooted, fast-growing edible winter crops, including rocket and coriander, on top of my dahlia bulbs. This year I am planning to try mizuna (Brassica juncea) and corn salad (also known as lamb's lettuce, Valerianella locusta) as well. By the time these crops are exhausted, the dahlia bulbs are beginning to sprout again.

Cactus-flowered dahlias in the garden of Sandra Wilson in Sydney

The tubers get rather congested after a while so need to be dug up and divided every few years around September (before they start to sprout) and replanted in soil which has been amended with plenty of compost and decayed manure. When the tubers are divided, each portion needs to have part of last year's stalk attached, or it will not regrow. Dahlias can also be propagated by taking cuttings of the new foliage shoots spring, which will grow quickly to form new plants. Dahlias make good cut flowers, as long as the cut end of the stem is sealed by being dipped briefly in boiling water.

Reader Comments

  • By Richard 2112 Monday, 29 February 2016

    I always thought dahlias to be very gauche and tacky, but have come to appreciate many of the smaller single flowered ones, including those with dark foliage and earthy tones, although I am only growing a couple at present. I love the tree dahlia D. imperialis, particularly the single mauve species form with a spectacular display of pendulous flowers in winter, and also grow the cultivar Timothy Hammett, which is slightly smaller and summer flowering, with more daisy like blue/purple flowers. Thanks, Richard. I too admire tree dahlias though I have given them away in my own garden. With garden dahlias, the small single-flowered ones do seem easiest to integrate with other blooms. Deirdre

  • By Evelyn 2117 Monday, 29 February 2016

    I also disliked dahlias but have just cleared a sunny spot and may try a smaller one there, having seen your column and seen a number of lovely ones around our neighbourhood. I also saw the comments about your garden in the paper at the weekend. Congratulations. How affirming to have a fellow gardener comment so positively about your garden. Evelyn Thanks so much, Evelyn. Hope you can find a smaller dahlia for your sunny spot. Deirdre

  • By Pam 2159 Monday, 29 February 2016

    Good to see the comments about you and your garden in the SMH. I have some large sized dahlia flowers - mainly gifts from friends. I have also grown hundreds from seed. The taller ones with very small pompom flowers are my favourites.They are mixed in with the shrubs and perennials. The colour range is lovely, and there are always flowers to add to a vase. Thanks so much, Pam. The pompom ones sound lovely. Dahlias are so good for a vase. Deirdre

  • By Sue 2074 Monday, 29 February 2016

    A lovely display from Sandra Wilson. Have come round to dahlias too, but this year they are not good due to a mite. Needed to eco oil/neem them early I guess, seems to be the same thing has attacked my bay tree as well. Your front garden looks lovely and the SMH article was good showing your plants for late summer gardens which seem so typically Sydney. Thanks, Sue. Yes I have sometimes had some strange leaf curling effects from an insect. Eco Pest Oil probably would be a good solution. Deirdre

  • By Anne 2518 Monday, 29 February 2016

    have always loved them! was sad when they went out of fashion. Mum had very big purple and salmon one and also a much loved rusty cactus flower which went on for years and years. I don"t lift mine and probably should give them more attention but it is lovely to see the different ones pop up each year. The smaller ones which come in "potted colour| are very rewarding too. Those ones of your Mum"s sound gorgeous! Deirdre

  • By Tracey 2158 Monday, 29 February 2016

    Once again thank you for your blog- you echo my sentiments exactly. I used to think Dahlias were horrible but now I am hunting them out! I have about 8 at present ., and they are on my must acquire more list! Dahlias are very easy care and rewarding and I too enjoy the therapy of dead heading. Thanks, Tracey! They are certainly good value and reliable in our climate. Deirdre

  • By Helen 7256 Monday, 29 February 2016

    They are a great standby & wonderful for cut flowers. I don"t always lift them either but sometimes lose a few if winter very wet. Great idea to everplant with rocket! Thanks, Helen. I do think that in colder climates there is the risk of losing them in a wet winter. Deirdre

  • By Nikki 7325 Monday, 29 February 2016

    I grew up in S Africa with a mother who specialised in Dahlias and daffodils. Last year I started my hot bed with, amongst other plants, about 6 single dark leaved dahlias, - red, yellow and burnt orange. I did not lift them in winter and this spring they came up like hairs on a dogs back. Many must have seeded themselves as they were quite a distance from the original tubers. Only problem now is the mixture of heights and colours - somewhat chaotic. Sounds amazing. I love them for a hot-coloured area. Deirdre

  • By Peta 2758 Tuesday, 01 March 2016

    Be a dare devil and plant the "dinner plate" Dahlias. Your life will never be quite the same again. Believe me! Anything is possible in gardening!!! Deirdre

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