To whinny muir

I’ve got a soft spot for one of New Zealand’s worst weeds (10 minute read)

To this day, the Lyke Wake Dirge remains one of my favourite songs. I love the stark tone of the rendition by Pentangle, with harmonic techniques dating back 1000 years giving the empty sound to the chorus, while simple modern harmonies brighten the verses. I learned to sing it with a small group at a time when I’d lost all joy in my voice, and it brought me back to singing again.

The lyrics of the song, with their pragmatic vision of divine justice, appealed to me too.

When thou from hence away art past,

To Whinny-muir thou com'st at last;

If ever thou gavest hosen and shoon,

Sit thee down and put them on;

If hosen and shoon thou ne'er gav'st nane

The whinnes sall prick thee to the bare bane;

For those not familiar with old forms of Yorkshire dialect, it refers to the souls of the dead arriving at a moor covered with whin, which is a viciously spiny shrub. Those who, during their lives, gave charity in the form of clothing (specifically shoes), would be allowed to wear those shoes as they crossed the moor. If they hadn’t, they would be walking through the spines barefoot.

The name whin isn’t widely used outside northern England and Scotland, but the shrub goes by other names too. Because it’s native to a wide area in western Europe, including Britain, it has a wide range of local names, including ajonc in France, gaspeldoorn in the Netherlands, Stechginster in Germany and tojo in Spain. But there’s a good chance that you’ve heard of it under its most widely-used common name – gorse.

image credit: Melanie Newfield

I found the imagery of the song particularly vivid, because, at the time I learned it, gorse featured prominently in my work. I worked for the Department of Conservation and my job was to advise the field offices around Nelson and Marlborough on weed management. There was no shortage of gorse in the region.

I once spent two days belly crawling under gorse bushes because it was the only way to control a new invasive weed, climbing asparagus, which had gained a roothold near an important reserve. On other occasions, I had trudged back and forth across grass and shrubland sites, counting exactly how many gorse bushes there were before the teams went in to spray them. I knew what it felt like to have whinnies pricking me to the bare bane. So, although I loved the song, I had a healthy respect for the plant, especially when it was dead. Meeting the spines of a dead gorse plant is much more painful than live gorse, as the dead spines break off and stay embedded in your skin.

Gorse, like many European species, was introduced to New Zealand with the best of intentions. Since the plant has converted all its leaves to spines, it makes an effective farm hedge. Charles Darwin spotted gorse hedges when he visited New Zealand in 1838. Gorse was widely sold prior to 1860, and hedges were planted from one end of New Zealand to the other. But it didn’t take long before people were finding it a little too vigorous. By 1860, the area around Nelson had a by-law requiring gorse hedges to be kept trimmed, because they were starting to obstruct the roads. And right in the centre of town, the area now occupied by the Cathedral became overrun with gorse.

Nelson appears to be the area where gorse first became a problem in New Zealand, but other areas quickly followed. By the 1870s, it was spreading in both the North and South Islands and people were beginning to consider it a nuisance. It became the subject of disputes between neighbours or landowners and tenants. In one case, the Māori owners of land which had been leased to settlers sued their tenants for allowing the land to become overgrown with gorse. They were awarded £65 in compensation.

By 1900, gorse was classed as a noxious weed because of its ability to completely take over pasture. But even as gorse was going wild from one end of New Zealand to the other, even as it was being classed as a noxious weed, it still had friends. Many English settlers retained their fondness for a well-trimmed gorse hedge and the cheery yellow flowers, which have the exotic aroma of coconut. Since they were effective at containing livestock, many people kept them. In fact, I can remember seeing them in Canterbury in the 1990s. Gorse was also promoted as forage crop – one proponent declared that it was likely to prove more beneficial to New Zealand than any other plant. This wasn’t an idea born of desperation – it had been used to feed livestock in Europe for centuries and is high in protein. However, it requires labour-intensive processing to make it suitable as feed, and it has to be prepared fresh every day. On New Zealand farms, where large numbers of animals ranged over a wide area, it was impractical.

New Zealand wasn’t alone in developing an ambivalent relationship with gorse. It was introduced to Africa, Reunion Island, Mauritius, Iran, India, Sri Lanka, China, New Guinea, Australia, North and South America, Hawai’i, the Caribbean and the Falkland Islands, mostly in the nineteenth century. As in New Zealand, it was used as a hedge, fed to livestock and considered a scourge.

One reason for the success of gorse is its ability to grow on poor soil. It belongs to a botanical group known as the legumes (it’s related to peas and beans). The roots of legumes have small nodules which provide a home for certain microbes, and the microbes have the ability to take nitrogen from the air and convert it into a form which plants can use for growth.

But there are other reasons that gorse has become such a problem. It grows well in a wide range of conditions, it produces large amounts of seed and few animals will eat it in its natural state. It also has remarkably long-lived seeds. The seeds have a thick shell around them which allows the seed to remain viable in the soil for decades. Gorse seed doesn’t travel particularly far from the plant – when ripe, the pods explode, sending seeds a few metres at most. As a result, the soil where gorse has been growing is full of gorse seed.

The large number of seeds in the soil sets up a cycle which allows gorse to defy our attempts to control it. Before the development of modern herbicides, the two main control techniques were physically removing the plants or burning them. Physical removal disturbs the soil, creating ideal conditions for seed germination. And which type of seed is most abundant in the soil where gorse has been removed? Gorse.

Burning has the same effect. If the fire isn’t particularly hot, gorse will resprout from the roots. In a hot fire, the roots are killed, as is the seed in the top layer of soil. But seed buried more than 5 cm will survive to grow new gorse plants. Gorse is extremely flammable, the most flammable of any common plant in New Zealand. As a result, areas dominated by gorse are at high risk of burning, and when they do, what grows back? More gorse.

There’s another reason for the success of gorse. When a species is transported to a new area, it may leave behind pests which eat it where it is native, called natural enemies. As a result, it may grow better in its new home than where it came from. This idea is one of the main theories for why species become invasive. It doesn’t necessarily apply in all cases, but there is evidence that it holds true for gorse.

If gorse became invasive partly because it escaped from natural enemies which eat it in Europe, is it possible to introduce those enemies and restore the balance? This is the idea behind biological control. But what if the enemies we introduce don’t confine themselves to attacking the species we want them to attack. Biological control went horribly wrong when stoats, ferrets and weasels were introduced to New Zealand to control rabbits, something I wrote about a few years back. But this disaster was entirely predictable – even in the 1870s there were people saying that the introduction was a bad idea.

Modern biological control uses rigorous testing to ensure that it only uses natural enemies which will eat the right thing. The testing is highly accurate, and means that biological control rarely has unexpected impacts these days. Gorse has been the subject of biological control research for years, and seven natural enemies have been released, although only six have established. It’s likely that these enemies are having some impact on gorse, but at times it’s hard to tell, because there’s still plenty of it around.

But there’s one more way of controlling gorse, and I don’t know how widely it is known outside New Zealand. Last year, I met some Hawai’ian invasive species experts who were concerned about gorse in some areas of Hawai’I, and they didn’t know about it. But for conservationists, it’s been a miracle.

Although it was well-known that gorse didn’t grow in the shade, and some ecologists were aware that areas of gorse could be taken over by native species, ecologist Hugh Wilson was the first to manage gorse with the aim of regenerating native forest. Hugh lives at Hinewai, an area of steep hills to the south of Christchurch. There, he showed if gorse was left in peace, with no burning, no spraying, no livestock or wild goats, it would shelter the seedlings of native plants. He didn’t plant the native plants there, they were brought in by birds from tiny remnants of forest in a few gullies. The native plants grew up through the gorse, forming a canopy over the top and killing the gorse. In the space of 10-30 years, depending on growing conditions, gorse would be replaced by native species.

When he began, people thought he was mad. But in just over a decade, by the time I was working on weed management in the Nelson region, his idea had become accepted wisdom in conservation circles.

One thing I learned as part of my work was that it didn’t apply everywhere. If the natural vegetation of an area was native forest, and there was enough rainfall, and there were trees nearby to provide seed, and it was warm enough, then it worked. But it didn’t apply in shrubland or a number of sensitive areas where there were low-growing native plants. Gorse still needed to be controlled in some areas to protect native plants.

Since Hugh’s mad idea, large areas which had been overrun with gorse have reverted to native forest, among them, the hills around Wellington. It doesn’t mean that the forest is exactly the same as it would have been without gorse. The resulting forest is not as diverse as native forest which regenerated through native kānuka, and the differences persist for decades. But it does mean that gorse is less abundant in many areas than it once was, with a corresponding decrease in the fire risk.

In one part of New Zealand, though, gorse itself is being protected. In the King Country, there’s an area of gorse-covered hill which was purchased by the Department of Conservation as a reserve. In 1987, when the land was still in private ownership, a rare species of wētā, the Mahoenui giant wētā, was found living in the gorse. Giant wētā are not like the tree wētā which are so abundant around Wellington, able to hold their own against introduced predators like rats. All giant wētā species are highly endangered, and most survive on predator-free islands. But the Mahoenui giant wētā clung to existence on the mainland by hiding from the predators among the dense spines of gorse. Without the gorse, it would be extinct today.

Gorse might be an invasive species around the world, a costly nuisance for farmers and a threat to natural environments in some places. But, like most invasive species, sometimes it causes problems and sometimes it doesn’t. So, in New Zealand at least, gorse still has friends.

It’s so commonplace in New Zealand that I seldom look at it closely. But it really is impressively spiny (image credit: Melanie Newfield)