Photinia 'Red Robin': the complete New Zealand hedging guide

Quick answer: Photinia 'Red Robin' puts on about 30 to 40cm a year in New Zealand, up to a metre in a warm season on good ground, and fills out in three to five years. Plant at 80 to 100cm spacing, trim in late spring to trigger a second red flush, and hold it at 1 to 2m. It needs free-draining soil. On heavy or wet ground you get leaf spot first, root rot second, and a gappy row after that.

Mid-October, and a well-grown Red Robin hedge does something none of our natives can manage. The whole top of it comes away scarlet, holds for a few weeks, then hardens off to glossy dark green for the rest of the year. Two hedges for the price of one.

It is also the plant we get the most questions about after something has gone wrong. Almost every one of them traces back to where it was planted rather than how it was looked after.

So here is the full picture on Photinia 'Red Robin': how fast it moves, how far apart to space it, how to get more red out of it, and the ground that will kill it.

How fast does a Red Robin hedge grow?

About 30 to 40cm a year, and up to a metre in a season where everything goes its way.

That figure comes from New Zealand nursery guidance and it matches what we see. Warm district, fertile free-draining soil, a bit of water through a dry spell and a feed once a year, and it will sit at the top of that range. Cold district, tight soil, no water, and you are at the bottom of it or below. Full size takes three to five years.

Left alone it will get to roughly 4m tall by 2m wide, but as a clipped hedge it is normally held at 1 to 2m tall by about 1m through. Anything over about 2.5m and you are into ladder work twice a year for the rest of your life, so pick the height before you plant, not after.

How far apart should you plant them?

80 to 100cm centres for a standard grade.

At that spacing the plants push each other upward for light and knit together at the base. Space them wider and you get two problems: a longer wait to close up, and a run of gaps at the bottom that never quite fill. For the sake of one or two extra plants per row it is not a saving.

When do you trim, and how do you get more red out of it?

Trim in late spring, once the first flush has hardened off. That is what triggers a second lot of red.

The red is new growth, nothing else. Every cut you make wakes up buds behind it, and those buds come away coloured. So a hedge that gets trimmed produces more red than a hedge left to its own devices. Growers usually work on two trims, late spring and late autumn, and that keeps it tidy while stretching the colour across a longer stretch of the season.

In a hard-frost district I would think twice about the late-autumn cut. A trim pushes soft new growth, and soft new growth in May around Alexandra or Riversdale meets a frost before it has hardened.

Why does drainage decide whether the hedge lives?

Because Photinia will not tolerate wet feet, and heavy ground kills it slowly enough that people blame something else.

Nursery guidance in New Zealand is blunt about this. Photinia does not grow well on heavy soils, clay included, and plants in that ground tend to die by degrees rather than all at once. The mechanism is phytophthora root rot. Roots sit in airless wet soil, they rot, the plant cannot draw water even though it is standing in it, and the top goes off colour and thin. By the time a row looks obviously sick, the roots have been gone for months.

If your line is on flat, tight ground that stays damp into November, you have three options. Fix the drainage properly. Raise the planting line on a mound or a low berm so the root zone sits above the wet. Or choose a different plant, which is the cheapest of the three.

What are the red and purple spots on the leaves?

Entomosporium leaf spot, a fungal disease, and it is the most common complaint on Red Robin anywhere in the world.

It shows up as small red to purple spots on the leaves. The spots enlarge, the leaf yellows around them, and the leaf drops early. A bad year strips the lower half of a hedge and leaves you looking at bare stems.

What brings it on:

• Long spells of wet weather, and cold wet winters in particular.

• Waterlogged or overwatered ground.

• Poor air movement, so foliage stays wet for hours after rain.

• Stress on a recently planted hedge that has not got its roots down yet.

What to do about it:

• Get the drainage right before planting. Same fix as the root rot, and it is the one that actually holds.

• Rake up and remove the fallen spotted leaves. The fungus overwinters on them and splashes back up onto the plant.

• Water at the base, never over the top of the foliage, and water in the morning if you can.

• Give the row a bit of airflow. A hedge jammed against a fence with a shed on the other side never dries out.

A mild dose most seasons is normal on Photinia and is cosmetic. A hedge that defoliates every year is telling you about the site.

Will Red Robin take a Southland or Central Otago frost?

Mostly yes on the coast, and with a caution inland.

The part that matters more in the deep south is timing. The red flush is soft, and it arrives in spring exactly when a late frost is still on the cards. Around Alexandra or up through inland Southland you can lose that first flush to a cold clear night in October. The plant recovers and pushes again, so it is a cosmetic hit rather than a fatal one, but a client who has paid for a red hedge deserves to know it may look brown for a fortnight first.

Where Red Robin does well down here is on the Canterbury plains and the free-draining shingle country. That ground drains hard and fast, which suits it, and the nor'wester is a wind problem rather than a root problem. On the flat wet paddocks around Winton, I would not put it in without doing something about the water first.

What would I plant instead if the ground stays wet?

Three natives we grow, each answering a different half of the question.

• Coprosma propinqua, mingimingi. This one grows naturally along stream banks and through swampy ground, so it takes wet ground that would finish a Photinia, and it takes hard frost, wind and salt on top of that. Small leaf, fine twiggy structure, 1 to 3m. The look is nothing like Red Robin, so go in with your eyes open.

• Coprosma 'Lobster' . The closest thing we stock to that red colour, and it holds it year-round rather than for a few weeks in spring. Frost hardy, tolerates wind, coastal exposure and dry once established. Sources put it anywhere from 1m to 2m x 1m, so treat it as a low to medium hedge. [It prefers free draining ground, and one supplier lists it as tolerating clay. Confirm with your own experience before you sell it as a wet-ground plant.]

• Pseudopanax 'Cyril Watson'. If the big glossy leaf is what drew you to Photinia, this is the native that carries the same visual weight. Narrow and upright, 2 to 3m by 1 to 1.5m, clips into a tidy formal hedge. It wants well-drained soil and takes light frost only. Young growth burns off in a hard frost, so it needs shelter for the first few winters inland.

None of these looks like a Red Robin - they answer the site rather than the picture.

What does a Red Robin hedge cost to plant?

The two grades we typically sell – 2.5L for $16.50ea +GST, and PB18 (10L) for $45ea +GST.

One thing on grades. A smaller plant on well-prepared ground catches a bigger one within a couple of seasons, because a small root system establishes faster and sulks less. If the ground is going to be difficult, spend the money on drainage rather than on plant size.

Common questions

Can I cut an old Red Robin hedge back hard?

Yes, it takes hard pruning better than most evergreens and reshoots from old wood. Do it in spring so it has the whole season to recover, and expect a plain green year before the colour comes back properly.

Does Red Robin flower?

It does. Small white flowers in spring, followed by red berries in autumn on plants that are not clipped tight. A hedge trimmed twice a year rarely flowers, because you cut the flowering wood off.

Is 'Red Robin' the same as Photinia 'Super Hedge' or 'Super Red'?

No, they are separate cultivars. 'Super Hedge' is faster, quoted at up to a metre a year, and denser, aimed at taller formal hedges of 1.5 to 3m. 'Super Red' has smaller leaves and the same colouring, going to about 5m untrimmed.

Can I plant a Red Robin hedge in winter?

Yes. Everything we grow is containerised, so it carries its own roots and mix and can go in almost any month. Autumn is still the best window down here because the soil holds summer warmth while the air cools, and winter planting works fine as long as the hole is not sitting in water.

Red Robin is a good hedge on the right ground and a slow disappointment on the wrong ground. Sort the drainage, get the spacing tight, trim it in late spring, and it will give you that scarlet fortnight every October for thirty years.

Contact us