Councils halt cultivation of Agapanthus plants
The Agapanthus plant may bloom beautiful purple flowers in summer, but if uncontrolled this popular plant can be a nightmare for native ecosystems and local councils. Natalie Muller reports.
There are many different types of Agapanthus, but only one is potentially invasive.
Its name is Agapanthus praecox subspecies orientalis, and the ease with which it can spread and self-seed has led some to label it a weed.
Yet this South African native is attractive to gardeners for the same reason it’s a pain for bushland.
“What you find with these types of weeds is that they are very popular because they are easy to grow,” said Chris Dewhurst, environmental coordinator at Blue Mountains City Council.
In some parts of the Blue Mountains, a World Heritage listed region, Agapanthus has spread from gardens into native bushland and national parks.
“They’re not such a problem for people who know how to manage them,” said Mr Dewhurst. “But if a person has a big area of Agapanthus at the edge of a garden on a mountain and they don’t manage it, in a couple of years you could see them spreading all the way down the slope.”
“It’s the people who leave their gardens unchecked that have the impact,” he said.
The Blue Mountains City Council has classified the Agapanthus praecox as an environmental weed – a plant that threatens natural ecosystems and diversity of fauna and flora.
“It can totally dominate the ground layer of the ecosystem and prevents natural regeneration,” Mr Dewhurst said. “So an ecosystem of 50 or 60 species can be reduced to just a handful of species. Lots of shrubs and birds becomes just a ground layer of Agapanthus and big trees.”
“[Weeds] are really the number one threat to our biodiversity up here,” he said.
The Agapanthus is a resilient plant, which can often displace all other vegetation with its dense root system. Its seeds are usually carried by water – through drainage systems and waterways – and spread outside garden limits.
“There’s not a lot of science to back it up,” said Dr Anthony Kachenko, national environmental and technical policy manager at Nursery and Garden Industry Australia. “A lot of it is anecdotal. People see it growing on the side of a park or the road and think it’s invasive when in reality someone has probably gone and dumped it there.”
Growing and selling the Agapanthus praecox is not illegal under the Noxious Weed Act, which regulates harmful weeds in NSW. Yet many local councils such as the Blue Mountains City Council strongly advise against planting them because of the potential dangers to native bushland areas.
Still, the Agapanthus is a popular choice for landscapers and gardeners and can be found in most big plant nurseries.
Alternative hybrid and sterile varieties have been developed to prevent easy spreading, but gardeners can also control their plants by chopping off the flower heads before seeds form.
Next year Blue Mountains City Council is launching a Bush friendly Nursery Scheme to promote nurseries who don’t grow and sell the Agapanthus praecox.
“It’ll provide a motive for nurseries to get on board with us and stop selling environmental weeds,” said Mr Dewhurst.
“When something is not noxious, it comes down to opinion,” he said. “Often you get a bit of disagreement about what’s a weed. Some nurseries say ‘it’s not a weed’ but others are very good about it and don’t sell these plants that can impact our environment.”
“It is quite a contentious topic,” said Dr Kachenko. “There is one particular species which is a potentially invasive species and it’s our advice to not grow them, but there are heaps of sterile types that are fine.”
In New Zealand, the Auckland Regional Council has gone a step further. Since 2007 Agapanthus praecox has been classified as a noxious weed. This means it is illegal to plant, sell, propagate or distribute the plant throughout the Auckland region, home to around a third of the New Zealand population.
Chris Roebuck owner of Auckland-based plant supplier Hortex Big Tree Limited, was surprised the laws were necessary. “You sometimes wonder where people get these noxious-weed ideas from,” he said.
Jack Craw, group manager of biosecurity at the Auckland Regional Council said the Agapanthus is a pest plant that spreads far too easily.
“The plant can naturalise into a variety of habitats, and forms dense stands particularly on the coastline, and out-competes native vegetation,” he said.
Some commercial growers gained exemptions from the law to be able to continue supplying the plant to buyers outside the Auckland region.
Others in the nursery industry have adapted.
“It hasn’t actually affected our business,” said David Addis, manager of Agapanthus Direct, a New Zealand supplier of Agapanthus. His business specialised in Agapanthus plants until he decided to expand his range a few years ago.
“Our business can’t just survive on one product, so we went on to lavender, buxus, azaleas [and others],” he said. “They still allow the dwarf variety [of Agapanthus] to be sold, so nurseries across New Zealand are still selling the varieties that aren’t invasive, and they’re also developing sterile varieties in laboratories that don’t self seed.”
The Auckland Regional Council is currently carrying out research, expected to be released next month, to determine whether the dwarf Agapanthus varieties can also be considered ‘weeds.’
Removing Agapanthus and other weeds from bushland areas is a costly affair for councils and for bush regeneration volunteers.
A Cost Benefit Analysis by Auckland Regional Council showed outlawing the Agapanthus praecox would save almost $1 million in the Auckland region each year.
“It’s a cost to the community because rate payers have to fund teams to go in and remove these weeds,” said Mr Dewhurst. “The Council would easily be spending over $700,000 a year on weed control.”
But despite the steep costs, the council feels it is better to teach the community how to control the Agapanthus rather than ban it altogether.
“People can choose whether they want to grow it or not. It’s a moral or ethical choice,” said Mr Dewhurst.
“We prefer to educate people and let them have the freedom to choose.”