A New Weapon in the War on Weeds

a yellow and black sign reads "caution spraying in progress" anlongside a sandstone wall and path

A sign warns that 'Spraying' is in progress. Photo Christopher Aronsten © Sydney Living Museums

On a crisp winter’s morning, in the gravel driveway between The Mint and the North Range of the Hyde Park Barracks, SLM Horticulturists Steve Halliday, Helder Esteves and Craig Field appear and disappear behind a shape shifting white cloud. A black and yellow sign warns me there is “Spraying in Progress”, and I wonder for a moment why no one is wearing a mask, or even gloves. But the dangerous looking mist enveloping these men is not what it seems.



the steam weeding machine is green and black and has a little chimney sticking out the top.

The Weedtechincs 'Green Ninja Stealth' in operation at The Mint.

Photo Christopher Aronsten © Sydney Living Museums

rear view of the black and green steam weeder sitting on a gravel road.

Operators view of the Steam Weeder with temperature and operating controls.

Photo Christopher Aronsten © Sydney Living Musuems

Next to them sits a black and green device, riding on mini off-road tyres. It looks like a cross between an air compressor, a diesel generator and very small steam train, and there’s a reason for that: it is.

Looking down into its dark heart, I see a hellish looking, diesel fuelled furnace, which is instantaneously heating the water being fed into it by an ordinary garden hose. The resulting product, a combination of steam and boiling water, is then fed down a long, heat shielded hose and finally, through a pin sized hole in the stainless steel head. What emerges, under 15PSI of pressure, is super-heated steam, and Steve and the team are using it to kill weeds.

the temperature guage on the steam weeder sits at 125 degrees

The optimal kill temperature is 125 degrees Celsius, this ensures the plants cell walls are decimated.

Photo Christopher Aronsten © Sydney Living Museums

an unplugged hose sits on the ground around a green ground cover plant.

The Steam Weeder runs on water and an everyday garden hose is all this is required. Tank water can also be used.

Photo Christopher Aronsten © Sydney Living Museums

“The big ones smell like blanched spinach”, says Helder Esteves, who looks like he should be cleaning carpets with the large, square-sided wand he’s waving over the gravel. He’s right about the smell. In fact the flat leafed specimens he’s just boiled to death have turned an intense, vibrant green and almost look delicious. But their rude health is just an illusion: by tomorrow, they will be full deceased, and a far less appetising shade of brown.

Using steam to kill unwanted moss and weeds is a relatively new practice for the SLM horticulture team, and the initial investment was significant compared to the low cost of the more commonly used glyphosate (often branded here as Round Up). The most obvious and immediate benefit of this new steam technology is that the substance being used in this age old battle with weeds is literally safe enough to drink. But look beneath the surface, and there’s a lot more going on.

A SLM staff member uses a steam weeding machine to kill weeds alongside the driveway at the mint.

Helder Esteves operates the machine keeping the head over the weeds for only a few seconds for instant wilt and the plant will waste away over the next few hours.

Photo Christopher Aronsten © Sydney Living Musuems

the after affect of the steam weeder showing the wilted winter grass amongst the gravel road

The results after steaming are immediate and you can tell the weed has been killed as it is now wilted and flat. This is winter grass - Poa anaua

Photo Christopher Aronsten © Sydney Living Museums

In the soil under every weed is a seed bank - a cache of siblings if you like, ready to take the place of any above-ground member of the family who is plucked, eaten or chemically destroyed. Being hidden under the surface used to offer some protection for these weeds-in-waiting. But super-heated steam is able to penetrate up to 5mm below the surface.

This deep heating causes some seed banks to be “denatured” and die on first treatment. For others, it actually triggers a mass germination, which in turn allows the seed bank to be rapidly depleted by repeated surface treatments. A spike attachment can be employed to kill the roots of bulbous grasses, and a smaller, more directional nozzle is used around garden beds to protect the other plants.

Two SLM staff members hold parts of the steam weeder as it is prepared to be loaded onto the trailer.

Helder and Steve dismantling the steam head and wand to prepare it for travel back to Vaucluse House.

Photo Christopher Aronsten © Sydney Living Musuems

SLM Horticulturists load the steam weeder onto the trailer ready for transport to another site!

Craig assists the machine onto the trailer as Steve winds the winch to haul up the heavy load.

Photo Christopher Aronsten © Sydney Living Museums

The machine’s official name is the Weedtechnics Green Ninja Stealth which was designed and invented by Australian Jeremy Winer. According the Weedtronics website, Winer’s “Satusteam” technology overcomes the issue of herbicide resistance, avoids off-target damage when chemicals are carried by the wind, preserves soil biology, protects ground water from chemical run off and is far safer than herbicides for the operator.

At the end of the operation, the Green Ninja is loaded on to the back of a trailer and driven to its next mission: teaching the tenacious nutgrass at Vaucluse House a lesson.

About the author

Chris Aronsten sits at a desk with a lamp to his right .

Chris Aronsten

Visitor Services Experience Officer

Chris Aronsten began work as a VSEO (Visitor Services Experience Officer) at the Hyde Park Barracks in February 2020.