Best Fast-Growing Hedges for NZ: Natives, Laurel or Photinia?

Picture the boundary you actually want. A solid green wall about shoulder height, soft in the wind, screening the neighbour's shed and taking the edge off the road noise while it's at it. A backdrop that quietly makes everything in front of it look tidier than it really is.

That's the picture nearly everyone has in their head when they ring up asking for a fast-growing hedge. Fair enough. A hedge is the one thing you plant for a version of your property that doesn't exist yet, and nobody wants to wait a decade to get there.

But fast has a catch, and picking on speed alone is how people end up with the wrong plant in the wrong spot.

What does “fast-growing” actually buy you?

Roughly half a metre to a metre of new growth a year on the quick ones, once they're established. That gets most hedges to a usable screen in three to five years rather than seven or eight.

The trade-offs are worth knowing before you fall for the number. Fast growers usually want more trimming to stay tidy. And a plant racing upward puts its energy into height before it thickens at the base, so you can be left with gaps down low if you don't tip-prune early. Speed tends to cost more per plant too, and the quickest option isn't always the hardiest.

Here's how the main contenders stack up for our conditions, natives first.

The natives: how fast, and where they suit

Pittosporum tenuifolium (kohuhu) is the classic fast native hedge for good reason. Growth of roughly 30 to 40cm a year in decent ground, more in a good spot, and a tidy 2 to 3 metre screen inside three to five years. The one rule: it hates wet feet. Keep it for free-draining ground, banks and raised beds, not the low soggy corner.

Griselinia littoralis 'Broadway Mint' is the bright glossy one everyone loves, and it's quick, roughly 40 to 60cm a year in a warm, sheltered spot. Two caveats though. Like Pittosporum, it can't stand sitting wet, which matters through a Southland winter when the ground stays cold and sodden for months. And it's only moderately frost hardy, so on a hard-frost inland site the fresh spring growth can blacken off. It usually pushes new shoots and recovers, but in the teeth of a Central Otago winter a young Griselinia can struggle without a bit of shelter.

Corokia is the tough one. It won't win the sprint, but once it's established there's little that bothers it, wind, frost, coastal salt and dry spells all roll off it, and it clips into a dense, structured wall as good as any native for a low to medium hedge. Growth is moderate to fair depending on the site, and it'll sit anywhere from about 1 to 3 metres depending on the cultivar. It wants the same free-draining, sunny ground as the others. If your site is exposed or brutal and you'll swap a bit of speed for a plant that just keeps going, this is the one I'd point you to.

Photinia 'Red Robin': the flashy one

Photinia is the hedge people plant for that red flush of new growth, and it does move at a fair clip, roughly 40 to 60cm a year, up to a metre in a really good season.

Two things to know. It needs free-draining soil or it sulks and thins out, same as the natives above. And that lovely soft red new growth is exactly what a hard frost or a dry, desiccating wind burns brownest. In a sheltered Canterbury or Central Otago garden it can look a picture. Out in an exposed frost hollow, or straight into a nor'wester, expect some burnt tips through the colder months. It grows back, but you're managing that look rather than avoiding it.

Portuguese laurel (Prunus lusitanica): the tough evergreen wall

If you're after big glossy leaves and a solid evergreen wall, this is the laurel I'd steer you

to ahead of the common cherry laurel. It's more refined, it clips tighter, and it's a good deal tougher in the cold, taking heavy frost down to around minus 15 without turning a hair. The trade-off is speed. Roughly 30 to 40cm a year, and slower again through a cold season, so you'll wait a bit longer than the quickest growers. What you get for the wait is a hardy, handsome hedge that holds its looks year in, year out.

One thing worth flagging if you run stock: like all the laurels it's a Prunus, and the leaves and berries carry cyanide compounds. It's less toxic than cherry laurel, but I'd still keep it, and its clippings, well away from anywhere an animal could graze. On a suburban section clear of stock, it's not an issue.

So which is actually the fastest?

On raw growth rate, a happy Photinia and Portuguese laurel lead the pack, roughly half a metre to a bit more a year in the right spot. Griselinia and Pittosporum sit a touch behind, and slower again in the cold. Corokia is in the moderate band but pays you back in toughness. And the bigger the grade you start with, the sooner you're at screen height, so the plant you buy matters as much as the name on the label.

Right plant, right place beats raw speed

The fastest hedge is the one that suits your patch, not the one with the biggest number on the label. So match it to your real problem:

• Wet Southland or low-lying ground: drainage is the killer, and none of these love wet feet. Pittosporum, Griselinia and Corokia all want free-draining soil, so on heavy or low ground lift them onto a mound or sort the drainage first. For a genuinely wet line, give us a call and we'll point you at a native that will actually cope with it.

• Central Otago hard frost: Photinia's soft growth and young Griselinia both feel it. Corokia and Portuguese laurel are the tough ones here, though I'd still give any new plant a season's shelter.

• Canterbury nor'wester: the wind desiccates new growth as much as any frost does. Shelter and watering-in matter more than the growth rate on the tag.

Get the plant matched to the site and “fast” takes care of itself. Get it wrong and no amount of speed saves it.

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