Possum bark stripping is a serious problem for New Zealand trees — both native species and ornamentals in home gardens. If caught early, many trees can recover with the right care, but severe ring-barking (where bark is stripped all the way around the trunk) can be fatal. Here's what to do.
Understand the Damage First
Before treating anything, assess how much bark has been removed. Bark protects the cambium layer — the thin living tissue just beneath the outer bark that carries water and nutrients between roots and leaves. The key questions are:
- How much of the circumference is affected? Damage covering less than about a third of the trunk's circumference gives the tree a good chance of recovery. Damage covering more than half is serious. Complete ring-barking (all the way around) is usually fatal, though some vigorous species can recover if treated quickly.
- How deep does it go? If the pale, smooth wood underneath is exposed, the cambium has been removed. If some green or moist tissue remains, there is more hope.
- How long ago did it happen? Fresh damage (edges still moist) responds better to treatment than old, dried-out wounds.
Clean and Protect the Wound
Once you've assessed the damage, take these steps:
- Remove loose or torn bark cleanly with a sharp, clean knife, cutting back to where the bark is firmly attached. Smooth, clean edges heal better than ragged ones — arborists call this wound tracing.
- Do not paint the wound with pruning paint or sealant. Modern arboricultural practice, supported by research, recommends leaving wounds open to the air. Sealants can trap moisture and encourage fungal rot. The exception is if your tree supplier or a qualified arborist specifically recommends a product for your species.
- Keep the area around the base of the tree clear of competing grass and weeds, and apply a ring of mulch (keeping it away from direct contact with the trunk) to reduce stress on the tree.
- Water the tree well during dry spells. A stressed tree has less energy to compartmentalise (wall off) the wound.
- For partial damage, some gardeners use bridge grafting — a technique where strips of bark or young shoots are grafted across the wound to restore the flow of nutrients. This is a skilled job best left to a qualified arborist.
Stop Possums Coming Back
Treating the wound is only half the job. If you don't deter possums, they'll be back.
Physical Barriers
- Possum guards (smooth metal or plastic collars fitted around the trunk) prevent possums climbing up from the ground. These are available from garden centres and hardware stores such as Bunnings and Mitre 10. They work best on isolated trees — possums can still jump across from nearby branches or fences.
- Trim branches that overhang fences or neighbouring trees to remove easy access routes.
Trapping and Baiting
Possums are a declared pest under the Biosecurity Act 1993, and controlling them is actively encouraged. You can legally trap possums on your own property using kill traps (such as Timms traps) without a permit. Poison baiting on private urban sections is more restricted — always check with your local council about what is permitted in your area, especially if you have pets or children.
For larger properties or persistent problems, your regional council or a professional pest controller can advise on bait stations and coordinated control programmes.
Repellents
Some homeowners have success with commercially available possum repellents applied around the base of the trunk, though results vary. Always follow label directions carefully.
Will My Tree Survive?
Recovery depends on the species, the extent of damage, and how quickly you act. Native trees like pōhutukawa, tōtara, and kāuri are particularly vulnerable to possum damage. Some fast-growing exotic species are more resilient. As a general guide:
| Damage Level | Outlook | Recommended Action |
|---|---|---|
| Less than 30% circumference | Good | Clean wound, protect, monitor |
| 30–60% circumference | Fair | Clean wound, reduce tree stress, consider arborist |
| More than 60% circumference | Poor | Consult arborist urgently |
| Complete ring-barking | Usually fatal | Arborist assessment essential |
Monitor the tree over the following growing season. New leaf growth and healthy colour are positive signs. Dieback from the tips of branches inward is a warning sign that the tree is struggling.
For guidance on protecting native trees specifically, your regional council's biodiversity or biosecurity team can be a useful contact.
When to Call a Professional
Call a qualified arborist if:
- The damage covers more than half the trunk's circumference
- The tree is large, valuable, or a protected native species
- You are considering bridge grafting
- The tree is near a building, power lines, or a boundary, and you're concerned it may become a hazard if it dies
- You're unsure whether the tree is worth saving or needs to be removed safely
A registered arborist can assess the tree's condition, recommend the best treatment, and advise on safe removal if necessary. You can find qualified local arborists on tradedirectory.co.nz.
Note: removing certain trees — particularly protected or notable trees — may require a resource consent from your local council. Always check before felling.
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