Portuguese laurel (Prunus lusitanica): a hardier laurel for cold sites

Quick answer: Portuguese laurel is hardy to about -15°C, grows 30 to 50cm a year, and clips to a dense evergreen hedge anywhere between 1.5 and 3m. It takes frost that browns off Griselinia, and it reshoots from bare old wood when you cut it hard. Two catches: it wants free-draining ground, and the leaves are poisonous to stock.

Walk along a Cromwell boundary on a July morning and you can read the hedges like a school report. The Griselinia is bronzed and blotchy along the windward face. The photinia has thinned out through its bottom third. And standing in the same frost, dark green, glossy, with red stalks showing through the leaf, is a laurel that nobody has had to make excuses for.

That plant is Portuguese laurel, and it is why the species keeps appearing on plans for the hard end of the South Island. It is the laurel that copes with cold.

So here is what I would want to know before ordering 80 of them.

How cold can it actually take?

Down to about -15°C. That puts it in a different class to the other glossy hedge options in the dry heart of Central Otago. Clyde, Cromwell and the Alexandra basin get frosts well past what a Griselinia will wear without blackening its soft growth every spring.

A first-winter plant is a different question. That figure is for an established plant with a proper root system under it, not a 2.5L that went in three weeks ago, and on an exposed inland site I would shelter a young row through its first winter.

The cold is not the thing that catches people out with this plant anyway. Wet ground is.

How fast does it grow, and how big does it get?

Around 30 to 50cm a year, at a steady rate rather than a fast one.

Mature size is really a question about how you manage it. Clipped as a hedge it holds at 3m by 1.5m. Left untrimmed it goes to 4 to 6m tall and 2 to 4m wide. Left alone for decades it makes a small tree of 10m and more. Same plant, three different jobs, and the only thing holding it at 2m is you, once or twice a year, for as long as you own the place.

Pick the height before the plants go in the ground, not in year four when somebody notices they cannot see over it.

How far apart do you plant it?

Half the height you intend to hold the hedge at.

• Held at 1m: 50cm centres.

• Held at 1.5m: 75cm centres.

• Held at 2m: 1m centres.

That is our rule for every hedge species and it is wider than most published figures, which are written from the height of the nursery plant rather than the height of the finished hedge. Wider spacing costs you perhaps one extra season before the row knits together. What you get back is a hedge whose plants are not fighting each other for water thirty years from now.

What happens if you cut it back hard?

It reshoots. That is the thing Portuguese laurel does that most of the popular evergreen hedges will not.

Cut a Griselinia or a Westringia back into bare old wood and you are gambling. Some of it comes away, some of it sits there grey and does nothing, and you end up with a gappy face you have to live with or replace. Laurel takes hard pruning and shearing and breaks new shoots out of old wood. So a hedge that got away over a wet summer, or one you inherited at 4m when you wanted 2m, is a recoverable situation rather than a rip-out.

Trim timing: main cut in late spring or early summer once it has flowered, with a light tidy later if the season has been kind. Trimming after flowering also takes off most of the developing berries, which matters for the next section.

Is it safe next to stock?

No. This is the part I want landscapers and farm clients to read twice.

Portuguese laurel sits in the cherry laurel group, and the whole group carries cyanogenic glycosides in the leaf. When plant tissue is damaged, the chemistry inside converts to hydrogen cyanide. Chewing does it. So does crushing, wilting, and freezing.

That last one is the reason this section belongs in a cold-site post. A frosted laurel leaf is damaged tissue. So is a heap of clippings sitting in the sun after a trim, and regrowth after a cut carries high glycoside levels too.

The case most often cited is from the Irish Veterinary Journal: 36 dairy-cross weanlings died over twelve days after going into a field bounded by a laurel hedge, where a number of the plants showed signs of having been chewed. Cattle are especially exposed because rumen microbes break the glycosides down fast.

Practical rules for a farm boundary at Mossburn or anywhere else with a wire fence and curious stock:

• Never throw laurel clippings over the fence into a paddock. Cut material is more dangerous than the standing hedge, not less.

• Do not plant it as a boundary hedge where stock can reach through and browse it. Put the fence line and the hedge far enough apart that noses do not meet leaves.

• If you're a landscaper putting this on a plan, raise it at quoting stage and put it in writing.

Cherry laurel (Prunus laurocerasus) is the worse of the two and we do not push it. Portuguese laurel is the safer one to handle and to have on a property. Safer is not safe.

Will it spread into the bush?

It can, birds eat the black berries and drop the seed, which is how a laurel from somebody's driveway ends up seeding into a gully three properties away.

Two things keep it sensible:

• Trim after flowering, every year, so the berries never get made in the first place. A clipped hedge is a much smaller seed source than a laurel left to grow into a tree.

• Think hard before putting it right up against native bush margins, gullies, waterways or reserve land. There are better choices for those edges and it costs you nothing to use one.

Where else would you leave it out?

Ground that stays wet. Portuguese laurel wants free-draining soil and gets root rot in heavy, sodden clay in the same way most of the glossy-leaf hedges do. In a Southland winter, when the next rainfall usually turns up before the last one has finished soaking away, that rules out a fair few paddock corners.

Deep shade under an established canopy will also slow it right down, though it takes more shade than most hedge species. And on a Methven or Rangiora site where the nor'wester comes through and pulls the moisture out of new growth faster than young roots can put it back, plan the first two summers of watering before you plant, not after.

Is there a native that does the same job?

Not the same look. The closest in habit is Myrsine divaricata [LINK: Myrsine divaricata (weeping mapou) product page], weeping mapou, a small-leaved evergreen with a soft weeping shape that clips into an unusual hedge and handles frost and free-draining ground well. It gets to a good height over time. Nelson and Canterbury growers list it to 6m if left to itself.

But it will never give you the big glossy leaf, the dark formal face and the red stalks. If that specific look is the brief, no New Zealand native does it, and I would rather say so than talk somebody into a substitute they will be disappointed by.

Common questions

What is the difference between Portuguese laurel and cherry laurel?

Different species in the same group. Portuguese laurel has smaller leaves with finely toothed edges and purplish-red leaf stalks, and its flower spikes are longer in proportion to the leaf. Cherry laurel has big, plain, paddle-shaped leaves. Cherry laurel is the more aggressive weed of the two and carries the higher toxicity.

Does it grow in shade?

Better than most hedging. Full sun to partial shade suits it best, and it will take a good deal more shade than that before it sulks. One of the few options for the south side of a building or under a high canopy, though expect it slower and more open there than in the sun.

What does it cost?

We sell the 2.5L grade at $16.50 plus GST retail, a PB18 (10L) grade for $45 + GST, and a 45L for $245 +GST. Landscapers/trade accounts will receive a discount off these prices.

Can I plant it in the middle of winter?

Yes. Everything we grow is containerised, so the plant carries its own roots and mix and can go in the ground almost any month. Autumn is the best window because the soil still holds some summer warmth while the air is cooling. Winter, including June and July, is fine. The awkward time is a late planting heading into a dry summer, when a plant with few roots can go thirsty before it establishes.

Portuguese laurel is a good answer to a narrow question: a formal, glossy, evergreen hedge on a cold, free-draining site, with the tolerance to be cut back hard if it ever gets away. Where there is stock over the fence or bush at the boundary, it is the wrong plant and there is no clever way around that.

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