How to Prune a Macrocarpa Hedge Without Killing It Back

Macrocarpa (Cupressus macrocarpa) is one of New Zealand's most popular hedging trees, valued for its fast growth and wind-hardiness — but it has one critical quirk: it will not regenerate from old, brown wood. Prune too hard into the dead zone and you'll be left with bare, brown patches that never recover. Follow the guidelines below and your hedge will stay dense, green, and healthy for decades.

Understand the Golden Rule: Never Cut Into Brown Wood

This is the single most important principle with macrocarpa. Unlike many deciduous hedges, macrocarpa and other cypress-family trees cannot bud from old, leafless wood. Always keep some green foliage on every branch you cut. If you can see brown, dead interior wood, stop cutting before you reach it. A good rule of thumb is to remove no more than one-third of the green growth in any one season.

When to Prune: Timing Matters

The best time to prune macrocarpa in New Zealand is late summer to early autumn (February to April). At this time:

• The main flush of growth has slowed, so regrowth is manageable.
• Warmer temperatures help the hedge recover before winter.
• Avoid pruning in the heat of midsummer, which can stress the tree and increase susceptibility to cypress canker (Seiridium cardinale), a serious fungal disease.
• Avoid heavy pruning in winter when growth is slow and wounds heal poorly.

For light tidying, a second light trim in late spring (October–November) after the main growth flush is fine.

Tools You'll Need

• Hedge trimmer (electric, battery, or petrol) for large flat faces
• Hand shears or loppers for thicker stems and detail work
• Pruning saw for any branches over about 25 mm diameter
• Disinfectant spray (a diluted bleach solution or methylated spirits) to sterilise blades between cuts — this is critical to prevent spreading cypress canker
• Safety glasses, gloves, and ear protection if using power tools

Keep blades sharp. Blunt tools crush stems rather than cutting cleanly, leaving ragged wounds that invite disease.

Step-by-Step Pruning Technique

1. Assess the hedge first

Walk the length of the hedge and identify any brown patches, dead branches, or signs of canker (resin oozing from bark, orange-brown discolouration). Mark these areas and deal with them separately.

2. Start with the sides

Trim the sides first, working from the bottom upward. Angle the sides very slightly inward toward the top — this battered or tapered profile allows light to reach the lower foliage, keeping the base dense and green rather than bare and leggy.

3. Do the top last

Once the sides are done, trim the top to your desired height. Cut just into the current season's green growth. If the hedge has grown taller than you want, reduce the height gradually over two or three seasons rather than all at once.

4. Remove dead material

Cut out any dead or cankered branches back to healthy green wood. Sterilise your tools before and after handling diseased material, and do not compost diseased cuttings — bag them for general waste.

5. Clean up thoroughly

Remove all clippings from around the base of the hedge. Decaying macrocarpa material can harbour fungal spores.

Dealing With Cypress Canker

Cypress canker is the biggest disease threat to macrocarpa hedges in NZ. Signs include:

• Sudden browning of individual branches or sections
• Resin or gum oozing from the bark
• Orange or brown streaking under the bark

There is no chemical cure — management relies on removing affected wood promptly, sterilising tools, and keeping the hedge healthy and unstressed. If canker is widespread, consult a qualified arborist. Plant health resources and your local council or a qualified arborist can provide further background on managing fungal disease in NZ conditions.

How Much Can You Safely Remove?

Safety Notes

When using power hedge trimmers, always:

• Keep the power cord clear of the cutting blade
• Use a residual current device (RCD) with electric tools
• Work from a stable platform — never overreach from a ladder
• Follow WorkSafe NZ guidelines for working at height

For hedges over about 2–3 metres tall, consider hiring a professional arborist with the right equipment.

When to Call a Professional

Call a qualified arborist if:

• Your hedge is very tall (over 3 m) and requires working at height with chainsaws or long-reach equipment
• You suspect widespread cypress canker and need an expert assessment
• The hedge is near power lines — this work must be carried out by, or in coordination with, your lines company
• You want to significantly reduce the size of a long-neglected hedge and need a staged recovery plan

A certified arborist will have the skills, insurance, and equipment to do the job safely. You can find qualified local arborists on tradedirectory.co.nz.

Sources & Further Reading

• WorkSafe NZ — Working Safely at Height

• MBIE Building Performance — Trees Near Buildings