The humble cabbage tree leaf proves a tough competitor at Wrybill Trophy Awards
What if the leaves of the humble tī kōuka (cabbage tree) could be used for a greener, more sustainable and profitable future?
That’s the question Yiting Su from Breens Intermediate explored in his winning science project at the 2025 Wrybill Trophy Awards event hosted by us.
His project, ‘From Tree to Treasure’, investigated the ways the tough fibrous leaves from the tī kōuka could be repurposed. These leaves can’t be put into our green waste bin but can be disposed of in the red bin (landfill) or at an Ecodrop for a fee. To reduce filling up our landfill bins with these leaves, Yiting thought of a way to put them to better use.
From backyard problem to science project
Yiting said the idea for his project came to him as he and his brother were picking up tī kōuka leaves while cleaning the yard.
“When I started doing some research, the word ‘fibre’ really caught my attention,” he said.
“Many garden centres that need fibres for things like small plant pots or flower basket mats rely on imported products like coconut fibres.
“I wanted to see if I could create a local solution using the fibres from tī kōuka leaves, resolving both the disposal problem of the leaves and creating a local solution to the demand for fibre-products.”
He designed three projects to test:
- Extracting tī kōuka leaf fibre
- Creating a water filter using tī kōuka leaf fibre
- Making fibre paper from tī kōuka leaf.
Yiting and his From Tree to Treasure display
Through his experiments, Yiting proved he could extract fibre with simple tools and that the fibres were flexible, making them easier to blend and shape than coconut fibres. Like coconut fibres, they have good water retention and biodegradability, and are durable enough to resist natural wear.
This confirmed his hypothesis that tī kōuka leaf fibre could easily replace imported coconut fibres in planting products, and for water protection (for example, erosion control blankets).
An innovative solution to a real-world problem
Yiting’s project was one of five judged by a panel made up of councillors Genevieve Robinson and Andrea Davis, and Lincoln University professor Jon Hickford. All three judges said the standard of projects gets better every year.
“This is my third year judging the Wrybill Trophy Awards, and the talent and passion of the students is incredible. Our future is in great hands,” said Councillor Robinson.
Professor Hickford said the judges were unanimous in their decision to award Yiting as the winner, but all the projects showed great use of either technology or scientific investigation.
“When choosing a winner, we look for a project that identifies a problem and demonstrates an innovative solution, and Yiting’s did just that,” he said.
“It has real potential for our local and national environment, as well as commercially.”
Chair Dr Deon Swiggs said that events such as the Wrybill Trophy Awards put the environment front of mind and are critical for where we’re heading as a society.
“It takes a lot of courage to stand up and present to councillors. The students have done an amazing job and I’m looking forward to following the progress of some of the projects.”
2025 Wrybill Trophy Awards finalists
The Wrybill Trophy Awards have been running since 2002.
To become a finalist, students must exhibit outstanding projects on environmental themes relating to our portfolios or workstreams, particularly around how we look after our natural resources while offering innovative solutions.
Each finalist won first place in their age category at their respective Science and Technology Fairs.
Canterbury-Westland (Christchurch)
- Junior: Yiting Su, year 8, Breens Intermediate with ‘From Tree to Treasure’ – an investigation into using cabbage tree leaves as natural filters for our waterways and a replacement for imported fibres.
- Senior: Cat Meharry, year 10, Cashmere High School with ‘Let It Slide’ – discussed which soil type is most likely to cause the biggest landslide.
Midland (Ashburton)
- Junior: Tom Johnson, year 8, St Joseph's School Ashburton with ‘Changes in nitrates’ – discussed what happens to nitrate levels in creeks and drains as water travels through farmland.
Central South Island (Timaru)
- Senior: Ella Metcalf and Jess Beeby, year 10, Craighead Diocesan School Timaru with ‘Waitarakao Lagoon - a wetland worth saving’ – an investigation into the historic state and use of Waitarakao Lagoon and the current state of its water quality.
- Junior: Holly Chapman, year 8, Ashburton Intermediate with ‘Does the Ashburton River have chemical pollution?’ – inspired by noticing differences in water quality from the headwaters to the lower river while tramping, this project investigates whether the Ashburton River shows signs of chemical pollution.