How to Prune a Young Rimu Tree Yourself: A NZ Homeowner's Guide

Pruning a young rimu (Dacrydium cupressinum) requires a careful, restrained approach — this is a treasured native conifer that generally needs very little intervention. In most cases, the best advice is to prune as little as possible and let the tree develop its natural form. That said, there are situations where light, careful pruning is appropriate and safe to do yourself.

Understand What Rimu Is Before You Start

Rimu is one of New Zealand's most iconic podocarp trees and is considered a taonga species. While young trees on private property are not automatically protected under the Resource Management Act (RMA), many councils have Notable or Significant Tree schedules that can apply even to trees on private land. Before doing anything, check with your local council to confirm whether your rimu is subject to any protection or whether a resource consent is required. Removing or significantly pruning a protected tree without consent can result in serious fines.

For general guidance on native trees and the building and resource consent framework, MBIE Building Performance is a useful starting point.

When Is Pruning Actually Necessary?

Young rimu trees are slow-growing and naturally self-shape over time. Pruning is generally only warranted when:

• A branch is dead, diseased, or damaged
• A branch poses a safety risk (e.g. growing toward a structure or pathway)
• There is crossing or rubbing between branches causing damage
• You need to lift the canopy slightly to allow light or access underneath

Avoid pruning simply for aesthetics or to speed up a particular shape — rimu has a distinctive weeping, layered form that should be respected and not forced.

Tools You Will Need

Using clean, sharp tools is essential to avoid tearing bark or introducing disease:

• Sharp bypass secateurs for small stems up to about 15 mm
• Pruning saw or folding saw for branches up to around 50 mm
• Loppers for mid-sized stems
• Pruning sealant (optional — current best practice is debated; check with your arborist)
• Isopropyl alcohol or methylated spirits to sterilise tools between cuts

You can find suitable tools at Bunnings or Mitre 10.

The Correct Pruning Technique

Make Clean Cuts at the Branch Collar

Always cut just outside the branch collar — the slightly swollen area where the branch meets the trunk or parent branch. Do not cut flush with the trunk (this damages the collar and slows healing) and do not leave a long stub (which can die back and invite disease).

The Three-Cut Method for Larger Branches

For any branch thicker than about 25–30 mm, use the three-cut method to prevent bark tearing:

1. Undercut — make a cut from below, about one-third of the way through, roughly 30 cm from the trunk
2. Top cut — cut from above, slightly further out than the undercut, until the branch falls cleanly
3. Final cut — remove the remaining stub just outside the branch collar

How Much to Remove

• Never remove more than 10–15% of the live canopy in a single season
• Avoid pruning in late autumn or winter when the tree is under stress and wounds heal more slowly — late spring to early summer is generally preferred
• Do not strip lower branches aggressively; rimu naturally retains lower branching when young

Safety Considerations

Work safely at all times. For any pruning above head height, use a stable ladder with a helper present. Never use a chainsaw on a ladder — this is a significant risk of serious injury. WorkSafe NZ provides guidance on working safely at height for homeowners.

If branches are near power lines, do not attempt the work yourself under any circumstances. Contact your lines company or a qualified arborist.

What You Should Not Do

• Do not top the tree — removing the central leader destroys the natural form of rimu and can cause long-term structural weakness
• Do not use wound paint indiscriminately — research from BRANZ and international arboricultural bodies suggests it rarely benefits the tree
• Do not prune during drought stress — wait until conditions improve
• Do not use a hedge trimmer or shear the foliage — rimu is not a hedge plant

When to Call a Professional

Call a qualified arborist (ideally one with NZ Arboricultural Association membership or a relevant trade qualification) if:

• The tree is large or the branches are beyond easy reach from the ground
• You are unsure whether the tree is protected by your council
• Branches are near power lines, structures, or neighbouring properties
• The tree shows signs of disease, pest damage, or structural weakness
• You want a full health assessment before deciding on any pruning

A qualified local arborist can assess your rimu properly and carry out any work safely and legally. You can find experienced arborists in your area at tradedirectory.co.nz.

Sources & Further Reading

• BRANZ – Building Research Association of NZ
• WorkSafe NZ – Working at Height
• MBIE Building Performance – Resource Consent and Trees
• Standards NZ
• Bunnings NZ – Garden Tools
• Mitre 10 NZ – Garden Tools