Crack willows can be a problem in streams because they grow too large and:

• Cause blockages and divert flows
• Drop branches which float downstream, lodge and re-grow
• Suck up water, reducing flows
• Shade out plantings.

In addition, they are often in the way of sensible fence lines. However, they protect the stream bank and bed from erosion, and their removal disturbs sediment.

Get a professional

If possible, get an experienced person to help you with your willow removal, especially for the really big trees. Willows are notoriously dangerous to fell.


In this photo willows were completely removed leading to erosion.

A strategy for willow removal

Above: Stumps are left to prevent bank erosion.

Below: Understorey willows removed and natives planted.

1. Clear out the understorey of small willows taking care to also remove all green woody material from the ground, such as willow branches and twigs. It is best to chip these and take them away, but alternatively you can just pile them up somewhere on site. This minimises the contact the bits of willow have with the ground and therefore the amount that sprout new shoots.
2. Leave an intact canopy of stable, straight willows. Taking out all the willows opens the ground to weed invasion. It may be necessary to remove some trees that are in the way of sensible fence lines, and are at risk of falling over and breaking fences or blocking the stream.
3. Plant native plants underneath the willow canopy. Refer to Planting & Maintenance booklet, Hardy plant table.
4. When your native plants are well established and a canopy of native plants is formed (5-10 years), kill the standing willows by drilling or hacking into the base and poisoning with glyphosate. Make sure you correctly follow the instructions and safety requirements of the herbicide. Note: If your natives are having trouble growing under the willows due to lack of sun, it may be necessary to remove some trees or branches to let in some light.
5. If you want to, wait until you are certain that the willows are dead and then fell them. It can take several months for them to die completely. It is important to either be trained or use a trained person for tree felling as it can be very dangerous. Don't worry about damaging the native plants as they will soon recover and fill in the gaps. It isn't necessary to remove or further break down the dead willows as they will not re-grow and will quickly rot.

A resource consent may be required for the removal of willows. Refer to Seeking advice on resource consents for your project.

For notes on other weed control methods see Planting & Maintenance booklet, Weed control prior to planting.

Look for threatened plants:

It is surprising how many threatened plants show up before any work begins, especially in overgrown and forgotten willow swamps. If a site is cleared and chemical is sprayed around, all these precious and usually quite inconspicuous gems will be lost.

Are you in a river rating district?

These areas have special management plans aimed at reducing the risk of flooding. If your stream is in one of these districts, you may be eligible for financial assistance to help with willow removal.

Contact Customer Services at Environment Canterbury to find out if you are in a river rating district and get advice. Phone 0800 324 636.

Checklist:

• Remove problem willows, but leave stumps to prevent erosion
• Where possible use contractors
• Don't blanket-spray following removal of willows
• Find out if you are in a river rating district.