Kill Your Willows Now, & Restore Native Life to Your Waterways

Nadia Crighton
1 day ago
4 min read

crack willow — Willows are amazingly adaptive. They grow rapidly, especially near water, and can regrow from even small cuttings.

Invasive willow trees may look beautiful lining a creek, but don’t be fooled, they’re a major ecological disruptor in New Zealand. Introduced species such as crack willow (Salix fragilis) can choke waterways, outcompete native plants, and dramatically alter ecosystems. The good news? Summer is the perfect time to get rid of them, and you don’t even need resource consent to kill them (only to remove them from the creek bed).

If you’ve got willows on your property, now is the time to act. Here’s how to do it right, and why it matters.

Why Willows Are a Problem

Willows are amazingly adaptive. They grow rapidly, especially near water, and can regrow from even small cuttings. A single broken branch can float downstream, take root, and begin a whole new colony. Over time, they:

Smother native vegetation
Disrupt natural water flow
Increase flood risks by blocking streams
Alter soil chemistry
Reduce habitat quality for native species

They’re tough, persistent, and highly invasive, which is why they need to go.

Summer: The Best Time to Drill & Fill

Between December and April, willows are actively growing and absorbing water. This makes them much more susceptible to herbicide treatment, which is why drill-and-fill methods work best during the hot months.

What Is "Drill and Fill"?

It's a targeted, highly effective way to kill willow trees without felling them right away:

Drill downward-facing holes around the base of the tree at soil level and along any exposed roots.
Spacing: Around 4–5 inches apart for smaller trees, and 9–12 inches for large willows.
Fill each hole immediately with a 50/50 solution of water and glyphosate (e.g. Roundup).

Important: Leave the tree standing. You need the leaves to stay intact as they help pull the chemical through the plant’s vascular system. If you cut the tree before treatment, it can become chemically resistant.

Common Mistakes to Avoid

Don’t cut the tree before drilling. You’ll reduce chemical uptake.
Don’t mulch the tree immediately after cutting. The mulch will retain chemicals that can harm nearby native plants.
Don’t plant new natives under branches that could fall. Safety first, plant around, not beneath.

What Happens After Drill & Fill?

Within 7–14 days, you should see signs of decline — yellowing leaves and dieback.
Let the tree stand for 1–2 months until fully dead.
Once confirmed dead, drop the tree safely and leave it for another month or two to allow the chemicals to break down before removing or mulching.
You can use the standing willow canopy as temporary cover for new natives. Once established, remove the willow to allow full sunlight.

Replant with Natives to Regenerate the Land

Another excellent tip is to use the wattle as a nursery for your new natives. Plant them carefully under the wattle, so they will not become crushed by a dying branch. This will keep the weeds down and allow your natives to flourish while you are waiting to remove the wattle once it is dead. Prioritise plants suited to your riparian or wetland area like:

Harakeke (flax) – for stabilising stream banks
Carex species (sedges) – ideal for erosion control
Kōwhai or mānuka – provide food for native birds and bees
Tōtara or kahikatea – long-term canopy trees for shade and structure

Replanting with natives not only restores ecological balance, but it also reduces maintenance, improves water quality, and enhances biodiversity.

Why Professional Help Matters

While it’s possible to kill willows yourself using the 50/50 glyphosate method, working with professionals ensures:

Proper chemical application (avoiding overspray or runoff)
Risk mitigation around waterways
Safe and efficient tree removal
Strategic planting that prevents future weed colonisation

At Native Restorations, we use proven methods and deep regional knowledge to tackle invasive willows effectively.

Don’t Forget the Climbers: Old Man’s Beard & Banana Passionfruit

Willows aren't the only problem. Vines like Old Man’s Beard (Clematis vitalba) and banana passionfruit are devastating to the native bush. Many will argue that banana passionfruit are pretty and tasty, but this little climbing sucker blankets canopies and kills native bushlands.

They are well known:

Smother canopies
Steal light from regenerating natives
Wrap tightly around mature trees, causing structural damage and death
Spread fast via tap roots and seed pods

The Right Way to Remove Them

Don’t rip them out in one go. That risks damaging the tree or bush they cling to.
Instead, drill and poison the main root and allow the plant to die back naturally, which may take up to a year.
Always monitor regrowth. These vines are persistent and need ongoing control.

Eradicating Invasives, Restoring Natives

If we’re serious about protecting Aotearoa’s natural landscapes, we need to take invasive species seriously. Willows, vines, and other pest plants are outcompeting our precious natives, but with smart, seasonal control and replanting, we can bring the bush back to life.

Now is the time to act. Summer is your window.

Whether you’re ready to tackle the willows yourself or need professional support, Native Restorations is here to help, across Marlborough, Nelson, Kaikōura and beyond.