‘If in doubt, throw it out’: How to identify wild mushrooms for consumption

The arrival of cooler temperatures signals the beginning of mushroom season in New Zealand, offering foragers an opportunity to collect an array of wild fungi that can add rich flavours to a sumptuous autumn dish.

However, experts warn foragers to exercise extreme caution when collecting wild mushrooms, as misidentifying and consuming a variety of fungi can cause illness and even death.

Are wild mushrooms ever safe to eat?

Liv Sisson, an Auckland-based forager and author of Fungi of Aotearoa: A Curious Forager's Field Guide, said there were an estimated 20,000 species of fungi in New Zealand, spanning both macro and microscopic varieties.

Despite this sizeable number, only 17 to 20 species were widely recognised as being edible, she said.

Sisson said there were no simple rules for identifying safe mushrooms in the wild, urging people to take extra care when foraging.

"There aren't any easy hacks - like colorful [mushrooms] are poisonous and brown ones are edible," she said. "You really have to be quite cautious. If you're in doubt, throw it out."

Sisson recommended newcomers to take guided tours or attend workshops led by experienced foragers to become familiar with different species.

David Orlovich, head of the University of Otago's Department of Botany and president of the Fungal Network of New Zealand, agreed.

Orlovich said most New Zealanders lacked knowledge of wild mushrooms, and foraging with an experienced expert remained the safest approach.

"We don't really have a huge culture of eating wild mushrooms compared to Asia or Europe," he said. "We haven't really got so much experience.

"There's certainly some indigenous knowledge that Māori ate or used certain species. But, on the whole, we don't have much knowledge or expertise on most of the species that are out there."

Orlovich said the similarities between mushroom species made it especially difficult to distinguish which were poisonous and which were safe to eat.

"It's really difficult because the differences between a lot of mushrooms are very subtle," he said. "Different mushrooms can look very similar: one might be edible, and one might be poisonous.

"The best advice I can give is to find someone who already knows which mushrooms are safe to eat and start learning from them."

Orlovich said people should also be cautious about information found online.

"You've got to be pretty careful, because sometimes it's hard to be completely certain just from a photograph," he said. "If you're not really sure, then you just have to throw it out."

What varieties of wild mushrooms are safe to eat?

While identifying wild mushrooms could be challenging, Sisson said a handful of edible species were considered safe for those who knew what to look for.

"At the moment, porcini is popping up, which is a highly prized edible mushroom," she said. "Lucky for foragers, it's a fairly easy one to identify.

"Birch boletes are also appearing now. And slippery jacks, which aren't as popular but can still be worked with in the kitchen."

She noted that wood ear is another common and easily identifiable mushroom.

"I quite like wood ear - that one's around all the time and is fairly easy to spot," she said.

"Shaggy mane is also coming up now. It's quite nice in pasta."

Sisson said foragers could search in a variety of environments - including backyards, paddocks, open grasslands and native bush - to find different species.

However, anyone searching for a prized porcini was advised to look near oak and pine trees.

What poisonous mushrooms should you avoid?

Death cap mushrooms, which look like a small white puff ball and often grow around the roots of trees, cause around 90 percent of mushroom-related deaths.

Symptoms typically appear within six to 24 hours after eating and cause liver and kidney failure, diarrhoea and vomiting.

Orlovich said the death cap, a highly poisonous mushroom introduced from the Northern Hemisphere and now found in New Zealand, was one that foragers should treat with extreme caution.

"The death cap looks a bit like another mushroom - the straw mushroom," he said. "So, I think people do get them confused, but that can have really deadly consequences.

"You'll be able to find pictures of that mushroom online or in books. Just be really sure that you haven't got something like that.

"The consequences of that will be really bad because you end up getting liver failure and ... multiple organ failure. And then that can lead to people dying of a heart attack in the end."

Can poison be removed from mushrooms through cooking?

Orlovich said there was a common misconception that toxins in mushrooms could be eliminated through cooking.

"There are lots of mushrooms where the poison is not denatured or destroyed by cooking - including the death cap," he said. "If you're cooking the death cap, the toxin will still be there after it's cooked."

Orlovich advised foragers to cook even edible mushrooms before eating.

"There are some edible mushrooms that also require cooking," he said. "There's one called the wood blewit. It needs to be cooked before you can eat it."

Sisson agreed, emphasizing that people should never consume mushrooms unless they are certain of the identification.

"There are misconceptions that you can cook out the toxins," she said. "If you're not sure of the species, throw it out."

How to tell if you've been poisoned by wild mushrooms？

Orlovich said there were several common symptoms to watch out for after eating poisonous mushrooms, and people should take them seriously.

"The most immediate and obvious symptom in most mushroom poisonings will be gastrointestinal upset," he said. "You have an upset stomach, nausea, maybe an increased heart rate, sweating - things like that."

"You may recover after a while, and that might be all you get."

However, he warned that in more serious cases, symptoms could be delayed - and potentially fatal.

"If you've eaten a death cap, you'll have those gastro symptoms and then may appear to get better," he said. "But then you start to get symptoms of liver failure. You might develop jaundice and start to feel very sick."

Orlovich said anyone who suspected they might have eaten a poisonous mushroom should go to their nearest emergency department immediately, and, if possible, bring a sample of the mushroom with them.

"If you have to go to the hospital, take the mushroom along to show them what you ate," he said.

As a safer alternative to foraging, Orlovich recommended growing mushrooms at home.

Where to seek help

The New Zealand National Poisons Centre strongly advises against consuming any wild or unidentified mushrooms.

Only mushrooms purchased from a supermarket or reputable market garden were considered safe, the centre said.

The centre also recommended removing any mushrooms growing in gardens before children or pets entered the area.

If someone has eaten an unknown mushroom, they should immediately call the National Poisons Centre at 0800 POISON (0800 764 766) for advice.

In such cases, any remaining residue should be removed from the mouth.

Vomiting should not be induced and, if possible, an intact sample of the mushroom should be kept for identification.