Dahlia dazzles in 2022 Trial Garden tests

The dahlia is Mexico’s national flower and Royal Botanic Garden Sydney horticulture aficionados say it is perfect for Sydney’s unique conditions. The violet-and-yellow petalled performer is one of the Top 16 winners in the 2022 Trial Garden competition.

The Trial Garden is located within the Palace Garden precinct near the Conservatorium of Music and now the experiments are done we are pleased to share the 2022 Top 16.

The Trial Garden was created in early 2017 to act as a source of information for the Garden and the thousands of green-thumb visitors. The data gathered is valuable to plant breeders and home gardeners alike and more information about how and why we trial plants can be read here. 

Last year the horticultural team trialed and tested cultivars of plants from across Australia and the globe to discover the Top 16 that prosper in Sydney’s humid subtropical climate, shifting from mild and cool in winter to warm and hot in the summer

Horticulture supervisor, Kate Burton, said Dahlia is a genus of tuberous plants that are members of the Asteraceae family, which also includes the sunflower, daisy, and chrysanthemum.

Kate said the Dahlia x hybrida Titoki Point cultivar, which featured in the trial, was bred by the eminent horticulturalist Dr Keith Hammett in New Zealand and is a very beautiful flower in terms of its colour, shape, and habit, which is the plant’s natural growth form.

“The pointed petals coupled with the single petal arrangement adds refinement to this bold flower. It is very popular with visitors and because it’s pest and disease free, grows well in Sydney gardens,” Kate said.

The growth of a plant is influenced by many factors - soil, temperature, water, exposure, and disease are just some of the elements that come into play.
“It’s not as simple as just planting something in the soil and watering it,” Kate said.

Hit or miss for kangaroo paw

The popular kangaroo paw, belonging to the genus Anigozanthos, is a good example of how the Trial Garden tested different varieties to guide the state’s gardeners.

“Because Anigozanthos is a Western Australian (WA) genus, there are varying conditions between WA and NSW that result in some species having ink spots, or fungal disease, and lack of vigour due to the humidity and rainfall,” Kate said.

“However, there are many new cultivars being released onto the market that are more disease resistant and can be successfully grown in Sydney,” she said.

Kate said the vibrant red-coloured Bush Gem Princess, which grows well in Sydney, and the grey-coloured Bush Gem Zest, which does not perform as well, were examples of how different varieties of kangaroo paws adapted to local conditions.

Putting plants to the test

The talented horticultural team at the Royal Botanic Garden Sydney trials several cultivars at the same time, which helps with a more visual comparison in the field. However, all trial plants are judged by the same criteria, depending on whether they are annuals, edibles or perennials.

These factors include habit, length of flowering, colour, presence of pest and disease, weeks to harvest and yield. Different plants will prefer and thrive in different conditions, just as different areas of Sydney and NSW, will have different soil, water and levels of exposure to the weather.