How stepping in the wrong patch of grass became a quintessential, if painful, Kiwi summer experience.

To start her third-ever summer, Ava went camping for the first time. Behind the dunes of the long, white-sanded Uretiti Beach in Northland, her parents and some of their friends set up their tents in a circle on the ground where grass had mostly dried out and the dirt was hard and dusty. That night, Ava played hide and seek with the adults. She raced around in bare feet, hiding between the tents’ flies and inner mesh or tucked into passenger seats of unlocked cars. Her pink Crocs, with their attendant Jibbitz, had wiggled off her feet. At 6am she woke up with a start. The adrenaline of play had worn off and now her feet ached. When she looked at them, dark points dotted her heels. Her eyes welled up, maybe with pain, and maybe with future nostalgia for a quintessential summer experience. Prickles.

Officially, the term prickle is “just for anything sharp that you get in your feet from the lawn”, says Kerry Harrington, New Zealand’s premier semi-retired weed scientist. A prickle can come from a range of plants – thistles, blackberries, speargrasses – but that’s just a technicality. On these isles we tend to use the word to mean one particular menace of the feet: Onehunga weed, or Soliva sessilis. In autumn, when the soil is moist but grass hasn’t quite recovered from summer thirst, its tiny, parsley-like leaves sprout. The plants grow throughout winter and then produce clusters of spined fruit, inconspicuous until they try to hitch a ride on an unsuspecting toe or just about anything else. The plant, one of the most hated in the country, is small enough to limbo under the blades of lawnmowers. 

It’s OK to hate Onehunga weed because it’s not native – the plant originally comes from South America. Which makes it another classic New Zealand thing that’s not really ours, like flat whites, Sam Neill and good relationships between the state and indigenous people. Still, Harrington says it’s probably been here for “centuries”. In 1883 an academic with the last name Cheeseman said the weed had “naturalised” in Auckland, and was named after the suburb where it was first noticed. Just over 100 years later, in 1988, the fourth volume of Flora of New Zealand noted Onehunga weed was widespread throughout the North Island, particularly north of Lake Taupō. In the South Island it was scattered in Nelson, Marlborough, Westland and Canterbury. It could be found in lawns, playing fields, golf courses, pastures and “stony waste places”. The authors commented that “further spread, by human dispersal, can be expected”.

“It spreads so easily,” says Harrington. He remembers a sweet period of his childhood in Napier when the family’s lawn didn’t have any prickles. Then, they went on a fateful camping trip to Taupō. “There was lots of it in the camping ground,” he says. When the family returned, they laid their tents out on the lawn to dry them out, inadvertently dispersing seeds that had pricked themselves onto the canvas. From then on, Onehunga weed plagued their lawn.

In 2002, members of the New Zealand Plant Conservation Network received a newsletter titled A prickly nuisance weed invading the south. It was a warning about the plant, “notorious for its painful foot-piercing spiny fruits”. Onehunga weed was appearing in an increasing number of sites around Otago and Southland, including a lawn in Invercargill, the Haast motorcamp, a gravelly airstrip in Fiordland, lawn verges around bus stops in suburban Dunedin and in the Dunedin Botanic Garden. The author, Peter Johnson, a scientist at Landcare Research, considered it to still be “in the early stages of invasion in the south”, so there was an opportunity to initiate control measures and limit its impacts. Emailing The Spinoff from his own semi-retirement, Johnson says that “local bodies and the like” didn’t take much notice of being alerted to the prickly nuisance. “In my experience people tend not to wish to know about yet another weed!”

Moth plant, a weed that doesn’t even have prickles, has a nationwide citizen society dedicated to stamping it out. Gorse, another prickly weed, has been the subject of much research and management programmes by local councils. By comparison, Onehunga weed seems to fly under the radar. Harrington has by accident found himself as a leading authority. “Nobody else has really had any reason to do any research on it,” he says. Because it’s small and sticks around places like lawns and campgrounds, it’s not considered an environmental weed. Those, like moth plant and gorse, can compete with native plants and upset natural ecosystems, so they’re targets of conservation efforts. It would be hard to say that a tiny weed that mostly grows on lawns, AKA domestic attempts at cultivating monocultures of exotic grass, is a threat to nature. Though they hurt our feet, prickles aren’t much of a pest.

That’s not to say weed control isn’t being carried out. Councils spray parks, sports fields, golf courses and around playgrounds. Specialised prickle killers are sold at garden and hardware shops. In Tauranga, there’s Prickleman, who promises to take the “Ouch!” out of people’s lawns. When people call Keith Williams, aka Prickleman, because someone’s foot has been pricked, it’s often too late, he says. Spraying is best done in spring, before the prickles form, and even then it’s not foolproof. “We have had maybe three or four instances where we’ve sprayed and then they haven’t died,” says Williams. “We’ve had to go and try different chemicals.”

In 1999, patches of Onehunga weed at the Helensville Golf Course northwest of Auckland didn’t die after the usual pesticide treatment. The plants looked a little different from usual – their leaves were sparse and thin. Harrington got on the case, and found it was a strain of Onehunga weed that was resistant to the common herbicides used to control it, clopyralid and picloram. Like its predecessor, this strain started to spread around the country – Mount Maunganui, Auckland, the Bay of Plenty and Palmerston North, where it was found around cricket wickets.Harrington thinks players’ shoes picked up prickles in other parts of the country, then dropped them there the next time they played. The solution is to use a different chemical, mecoprop. The other option, not for the faint of heart, is to manually remove plants. Ideally, people would “just check their jandals and make sure they haven’t got prickles in the bottom”.

So are prickles a uniquely New Zealand experience? While those who grew up overseas might not have such strong childhood memories of prickles as many of us who spent our childhoods in Aotearoa, not quite. Soliva sessilis can be found in different guises (lawn burrweed, lawnweed, jo-jo weed and bindi) in heaps of places including the US, France and Australia. With the exception of our trans-Tasman neighbour, others don’t use the term prickles primarily to refer to Soliva sessilis. They also consider rose thorns, thistles and brambles to be prickles and of equal annoyance. So what’s the difference between us and those who don’t have their feet turned into pin cushions each summer? Probably the fact that down here, we’re always running around barefoot outside, kids especially. Our no-fuss outdoorsy Antipodean lifestyle makes us fun, adventurous, sun-kissed and susceptible to those little spikes. A recent prickle-focused episode of the Australian worldwide kids TV phenomenon Bluey had American viewers confused, inspiring an entire reddit thread.

After her mum fished the prickles out of her heel with tweezers, Ava ran off to get her orange ball. One of her Crocs lay by the entrance of the tent, and the other was nowhere to be seen. Her first encounter with prickles will most certainly not be her last.