Up to 40 ailing willow trees along the banks of Kā Pūtahi Creek in Englefield Reserve will be removed and replaced with native trees, helping to stabilise the banks and reduce sediment build-up.
The project is being delivered jointly by the Christchurch City Council Three Waters team alongside the Council Parks team.
Certain willow trees are considered a pest tree on waterways, where they can proliferate and suppress native plantings and regeneration. They also produce heavy leaf fall in autumn which can de-oxygenate the water, making it difficult for fish and invertebrates to survive.
The 40 trees to be removed are all on the true left bank of Kā Pūtahi Creek, a tributary of the Pūharakekenui/Styx River and are either unhealthy or structurally unsound. Around five willows will be retained because they offer benefits such as nesting cavities for wildlife.
Existing native plantings along the bank that are now becoming being suppressed by the willow canopy include a number of kahikatea estimated to be more than 15 years old.
“Although we will be removing 40 mature willows, the loss of existing tree canopy will be minimal because of this understory,” says Christchurch City Council Community Parks Manager, Al Hardy.
“As part of the project we will also be planting approximately 2800 riparian plants along the creek bank, including more than 1000 eco-sourced canopy-forming native trees, which will replace any lost canopy within 20 years.”
Eco-sourcing is the practice of collecting seeds close to where they are going to be planted, meaning the plants will be suited to local conditions and more likely to survive.
In conjunction with the project, Styx Living Laboratory Trust is going to plant a 15-20m wide area of low-lying floodplain between the project site and the Englefield Reserve playground.
This area is currently managed as rough-mown grass, however it is wet throughout the year, making mowing difficult.
The Trust has partnered with TreeTech’s ‘Green Gear’ company and Trees for Canterbury to supply, plant and maintain the additional forest plantings in the reserve as part of its Ministry for the Environment Freshwater Improvement Fund project - ‘Project Kotare’.
The willow removal work will take place over April/May, and the bank renewal and instream enhancement work over the summer months. Final replanting of the riparian corridor will be completed by June next year.
Christchurch City Council has adopted the 2000-2040 Styx Vision with the aim of restoring and establishing a spring-fed ecosystem throughout the length of the river and its tributaries.