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This article was written by Karolin MacGregor and was published in Tasmanian Country Newspaper on 12 January 2024.
It is fast becoming one of Tasmania's most invasive weeds but at this stage not much is known about the fish-tail Oxalis.
Tasmanian Institute of Agriculture PhD candidate Laurie Krauss is undertaking a 3 1/2 year research project to learn more about the weed, where it is and, importantly, how to control it.
Ms Krauss spoke to participants at a Forthside Research Facility Field Day and said up until now, Oxalis was a weed that had been flying under the radar.
Originally from Mexico, it is known as fishtail Oxalis because of the unusual shape of its leaves and it has spread throughout the world in temperate and sub-tropical zones.
"It has the ability to spread quite rapidly because it's a unusual plant because it is a broad leaf plant that comes from a bulb, which is quite rare in the plant kingdom. "Being a bulb, it has the ability to survive in quite harsh conditions," Ms Krauss said.
One of the things Ms Krauss is trying to find out is where the weed is located across the state.
"We don't know where it is in Tasmania and we don't have any definitive data," she said.
"We need that base line so we can say in 2024 it was in these locations and now we've found it in other locations that haven't been reported before so we want to see whether it's spreading. It could be sneaking under the radar." Because it is a bulb, traditional cultivation can break up the bulb clumps making it easy to spread in soil.
Ms Krauss said her research was focused on finding better control and eradication methods.
"That's the vital part of my research, finding out when is the best time for defoliation," she said.
"There hasn't been any research done in Tasmania and it's becoming a problem on a lot of farms because growers, agronomist and industry don't know how to get rid of it. Short fallows, selective herbicides and cultivation don't work. It's a very resilient plant and it can gradually take over a whole paddock."
Ms Krauss said controlling the weed in crops such as potatoes or onions was almost impossible because the usual sprays for broad leaf or bulb plants will also impact the crops.
The weed was first discovered in Hobart in 1945, but Ms Krauss said it had probably been in the state since the late 1800s after being brought in as an ornamental plant.
It can spread through gardens and it has also been found in potting mix with plants from major nursery retailers.
Oxalis plants can be eaten by livestock, but it will cause kidney problems if too much is ingested.
Ms Krauss said the plant's ability to produce large amounts of bulbs meant it could spread rapidly.
"If it's not controlled, we're going to have a lot of problems," she said.
Ms Krauss said where the weed cannot be controlled, sometimes whole paddocks need to be taken out of production.
Ms Krauss is encouraging any farmers who may have the weed on their properties to get in touch.
"Farmers who would like to talk to me are most welcome to and I would like to talk to people who may think they have it or do have it and are unsure what to do with it," she said.
Contact Laurie Krauss via email: laurie.krauss@utas.edu.au