Willows are a group of introduced tree species which that were brought to New Zealand in the early 1800s and widely planted for bank stability. Since then, willows have replaced native wetland and river-bank vegetation in many places.

If well managed, or the right species, willows can contribute to bank stability and offer positive benefits to wildlife. However, in the wrong place, willows can block streams causing flooding, and scour stream banks.

There are rules which may apply to the removal of willows from in and around rivers, lakes, and wetlands.

What rules apply will depend on where the willow is located and the method you use to remove them.

Please check the rules if you are planning to remove willow from:

• within the bed of rivers or lakes
• along the bank of rivers or lakes
• within a wetland or
• within a 10m setback from a wetland

If you are unsure if your activity requires resource consent, please get in touch with us by emailing consent.enquiries@orc.govt.nz or call 0800 474 082.

External resources on willow control are listed below. Before you get started, it is important to check if resource consent is needed by contacting ORC’s consents team at consent.enquiries@orc.govt.nz. If you think willows are causing a flood or erosion problem on publicly owned land, contact engineering@orc.govt.nz. Otherwise, here is a summary of things to consider:

• Clarity on your objectives and timeframes for willow control. This is especially so where you plan to establish native riparian planting – separate guidance on suitable riparian planting can be found on our Good Practice, page as well as some of the references below.
• Make sure you engage with all landowners in the target area. Often this will be a public agency, including ORC and DOC. You can identify public agencies via the Walking Access website.
• Appropriate control methods, given the target area, and the skills and resources available. Methods include:
  • drill & inject herbicide, basal bark spray, cut stump painting.
  • heli-spraying herbicide on large dense mature canopies.
  • mechanical removal, from hand cutting tools to chainsaws and excavators.
• Spraying is much more effective in early autumn when the herbicide will be drawn down to the root system.
• The use of diggers with cutting shears, chainsaws and grapples will be more effective when used after autumn spraying so that the tree is ‘standing dead’. This greatly reduces the risk of redistributing live stem fragments which can resprout.
• Disposal options include mulching, stack burning (while avoiding smoke nuisance), chipping, removal, or leave to rot in situ (after spraying). Any debris piles must be stacked above flood levels.
• Establishing native revegetation: staging, with pioneer species planting beneath standing dead willows.
• Ongoing maintenance to check and control for regrowth.
• Health & safety, especially in relation to machinery and herbicide use, and working next to waterways.

• Willows and Alders: Best practice guidelines for Willow and Alder control for riparian restoration for the Waikato This practical 2015 guide was prepared by NZ Landcare Trust and Waikato Raupatu River Trust. It emphasises the need for clear achievable objectives as well as which control methods to select.
• The Weeds chapter of the 2012 Wetland Restoration Handbook prepared by Manaaki Whenua Landcare Research.
• Managing Wetlands as Farm Assets was a Canterbury-based project led by Landcare Trust. Several of the wetland restoration projects involved willow removal, with practical guides and short farmer videos.
• Integrating native planting and flood protection is a 2021 operational guide for Greater Wellington Regional Council that deals with broader riparian management issues, including the scope to progressively introduce natives into a willow-dominated river margin.
• Weedbusters information on Crack Willow – this includes practical guidance on herbicide treatment methods.
• Tane’s Tree Trust article ‘What is it with Willows – pest, resource or opportunity for native forest?’

Central Otago’s Thomsons Catchment Project includes a large, constructed wetland with extensive native planting to replace pasture and a stand of old willows.

The Te Nohoaka o Tukiauau/ Sinclair Wetlands are a major protected wetland complex in the lower Taieri catchment, owned by Kāi Tahu. Aerial spraying of invasive willows and ongoing maintenance control helps maintain the wetland native biodiversity.

The Tiaki Maniototo project in the upper Taieri catchment includes extensive riparian and wetland willow removal, with associated fencing and planting work.