A tree struck by lightning can look dramatically damaged — or surprisingly normal — yet still be seriously injured inside. The good news is that many trees do survive lightning strikes, especially if they receive prompt, appropriate care. Here's what to do in the hours, days, and weeks after a strike.
Stay Safe First
Before you go anywhere near the tree, make sure the scene is safe. Lightning can travel through roots and wet soil, so do not approach the tree during or immediately after a storm. Check for:
- Fallen or hanging branches (called widow-makers) that could drop without warning
- Downed power lines — if any lines are near or touching the tree, stay well clear and call your lines company immediately
- Structural lean or root heave that suggests the tree could fall
If there are power lines involved, contact your electricity network operator and do not attempt any work yourself. This is a situation where you must wait for professionals. For general electrical safety guidance, refer to WorkSafe NZ.
Assess the Damage
Lightning damage varies enormously. The bolt may have:
- Stripped bark in a spiral or straight line down the trunk
- Exploded sections of wood outward
- Caused internal damage with little visible sign on the outside
- Split the tree or shattered major limbs
Take photos from multiple angles. This helps you track recovery over time and is useful if you need to consult an arborist or make an insurance claim.
Signs the Tree Is Likely Beyond Saving
- The trunk is split to the ground or more than 50% of the crown is destroyed
- The root plate has lifted or the tree is leaning significantly
- The bark is stripped away around the full circumference (called girdling), which cuts off the tree's ability to move water and nutrients
If you see any of these, removal is likely the safest and most practical outcome.
Immediate Care Steps
If the tree appears structurally sound and the damage is partial, take these steps:
1. Water Deeply
Lightning superheats the moisture in a tree's tissues, causing severe internal stress. Deep, slow watering in the days following a strike helps the tree begin recovery. Soak the root zone — roughly out to the drip line of the canopy — rather than just watering at the base of the trunk.
2. Remove Broken Branches Carefully
Broken or hanging branches are a safety hazard and should be removed promptly. Use clean, sharp tools and make proper pruning cuts just outside the branch collar. Do not leave stubs, as these invite disease and decay. For anything above head height or requiring a chainsaw, call a qualified arborist.
3. Avoid Heavy Fertilising
It's tempting to give a stressed tree a nutrient boost, but heavy fertilising immediately after a strike can actually increase stress. Hold off on fertiliser for at least a few months, then consider a slow-release, balanced product if the tree is showing signs of recovery.
4. Do Not Apply Wound Paint or Sealants
Older advice recommended painting over pruning cuts and damaged bark, but current arboricultural practice — supported by research — is to leave wounds open to callus naturally. Sealants can trap moisture and encourage fungal decay.
5. Mulch the Root Zone
Apply a 75–100 mm layer of untreated wood chip mulch over the root zone, keeping it 100–150 mm away from the trunk. This retains soil moisture, moderates temperature, and reduces competition from grass and weeds — all of which help a stressed tree recover.
Monitor Recovery Over Time
Lightning-struck trees can take one to three growing seasons to show whether they will fully recover. Watch for:
- New leaf and shoot growth — a positive sign
- Dieback progressing down branches — a warning sign
- Fungal fruiting bodies (mushrooms or conks) on the trunk or roots — indicates internal decay
- Unusual lean or root movement — a structural safety concern
Keep a photographic record every few months. If you notice ongoing decline, consult an arborist sooner rather than later. BRANZ has useful general guidance on tree and property interactions that may also be relevant if the tree is close to a structure.
Trees Near Buildings: Consent and Liability
If a lightning-struck tree is near your house, boundary, or a neighbour's property, be aware of your obligations. A damaged tree that later falls and causes injury or property damage could expose you to liability if you were aware of the risk and did nothing. Check with your local council about any tree protection orders or district plan rules that may apply before removing or significantly pruning the tree — some trees require a resource consent to remove even if they are damaged. Your council's planning team is the right first point of contact.
When to Call a Professional
Call a qualified arborist if:
- The tree is large, near a building, or over a public area
- There are hanging or broken branches above head height
- You are unsure whether the tree is safe to remain standing
- The damage involves power lines (call your lines company first)
- You want a professional assessment of the tree's long-term viability
A New Zealand Arboricultural Association (NZAA) certified arborist or similar qualified professional can carry out a formal risk assessment and recommend the right course of action. You can find qualified local arborists on tradedirectory.co.nz.
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