Can I Use Herbicide to Kill a Tree Stump Yourself?

Yes, in most cases you can use herbicide to kill a tree stump yourself — it's a practical, low-cost option that many Kiwi homeowners tackle successfully. That said, there are important safety considerations, product choices, and situations where calling a qualified arborist is the smarter move.

How Stump Herbicide Treatment Works

When a tree is cut down, the stump and root system often remain alive and can resprout. Applying herbicide directly to the freshly cut stump surface (or through drilled holes) kills the living tissue and prevents regrowth. This method is generally more effective than leaving the stump to rot on its own, and far less labour-intensive than mechanical stump grinding.

The two most common application methods are:

• Cut-surface (or cut-stump) treatment — Apply herbicide immediately to the freshly cut surface of the stump, ideally within a few minutes of cutting.
• Drill-and-fill treatment — Drill a series of angled holes around the stump and fill them with concentrated herbicide solution. This works well on older stumps that have already dried out on the surface.

Choosing the Right Herbicide

Not all herbicides are suitable for stump treatment. In New Zealand, the most commonly used active ingredients for this purpose are:

• Triclopyr — Highly effective on broadleaf trees and woody species. Often sold as a ready-to-use or concentrate product at hardware stores.
• Glyphosate — Widely available and effective on many species, though less reliable on some hardwoods. Best used at higher concentrations for stump treatment — check the product label for the recommended rate.
• Metsulfuron-methyl — Very effective on a wide range of species including some invasive trees, but requires more care around other plants and waterways.

Always read the product label carefully — it is a legal requirement in NZ to use any herbicide according to its label instructions under the HSNO Act 1996. Products are available from Bunnings and Mitre 10, and staff can help you find a stump-treatment product suited to your tree species.

Step-by-Step: Cut-Stump Treatment

1. Cut the tree as low as possible — the closer to the ground, the better.
2. Act quickly — apply herbicide within 5–10 minutes of cutting, before the surface dries or oxidises.
3. Apply to the cambium layer — this is the ring of living tissue just inside the bark. Concentrate the herbicide around the outer edge rather than the centre.
4. Use a paintbrush, squeeze bottle, or spray — avoid runoff onto surrounding soil or plants.
5. Mark the stump so others know it has been treated.
6. Repeat if needed — some species (particularly wattles, willows, and poplars) may resprout and require a second treatment.

Safety First

Always wear appropriate PPE: gloves, eye protection, and long sleeves when handling herbicide concentrates. Keep children and pets away from treated areas until the product has dried, as per label instructions. Store herbicides in their original containers, out of reach of children.

Be especially careful near waterways, vegetable gardens, and neighbouring properties. Some herbicides are restricted near water — check the product label and, if in doubt, contact WorkSafe NZ or your local council for guidance on safe use near sensitive areas.

NZ-Specific Considerations

• Invasive species: If you're dealing with a pest plant listed under your regional council's pest management plan (such as woolly nightshade, crack willow, or old man's beard), there may be specific requirements or even assistance available for control. Check with your regional council.
• Protected trees: Some trees are protected under the Resource Management Act (RMA) or local district plan rules. Before removing or treating any tree, confirm with your local council that you don't need resource consent. This is particularly important for large trees, trees in notable locations, or trees in certain zones.
• Neighbouring trees: If the stump is near a boundary, be aware that herbicide can travel through interconnected root systems and potentially affect neighbouring trees.

How Long Does It Take?

Results vary by species, stump size, and time of year. Most treated stumps will show signs of die-back within a few weeks, but full death of the root system can take several months to over a year. Treating in spring or early summer (when the tree is actively growing) generally gives the best results, as the plant is drawing nutrients down into the roots.

When to Call a Professional

While stump herbicide treatment is a legitimate DIY task, there are situations where it's best to bring in a qualified arborist:

• The tree is large or the stump is extensive, with a root system that could affect structures, drains, or neighbouring properties.
• The tree species is particularly difficult to kill (e.g., some eucalypts, poplars, or tree privet) and repeated treatments haven't worked.
• The stump is close to a waterway, and you're unsure which products are safe to use.
• You need the stump physically removed — stump grinding is a job for a professional with the right machinery.
• You're unsure whether the tree is protected under local rules.

A qualified arborist can assess the situation, recommend the most effective treatment, and handle disposal safely. You can find experienced local arborists on tradedirectory.co.nz.

Sources & Further Reading

• WorkSafe NZ – Safe use of agrichemicals
• BRANZ – Trees and buildings
• MBIE Building Performance – Resource consent and trees
• Bunnings NZ – Herbicide products
• Mitre 10 NZ – Garden care products