The kiwi's the national bird and the pavlova the national pudding, but what is the national fungus?

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Scientific American blogger Jennifer Frazer recently visited New Zealand and has nominated one species on the basis that its mushrooms are 'all black'.

She said Tylopilus formosus is possibly our most patriotic fungus.

But deciding on a national fungal emblem could be a contentious matter, given there are tens of thousands of species in New Zealand - plus a small number of experts who have their personal favourites.

Attendees at the annual National Fungal Foray on the West Coast this week were asked to nominate their favourites.

Some felt New Zealand already has a de facto national fungus: one known as the blue Entoloma.

If you have a $50 bill then you're in luck - and not just because you've got fifty bucks. You'll also be able to see this blue mushroom depicted on what is the only banknote in any currency with a picture of a fungus on it.

A bit of a superstar, the blue Entoloma has also been on the cover of the 80 cent stamp.

In native forests it's quite a standout against background greens and browns, matched only in its blue-ness by the wattle of the kōkako.

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However, some mycologists disqualified it as a pick for national fungus, partly because blue Entolomas are found in several other countries, and partly because they think it's a bit ordinary, as fungi go.

There's some consensus in favour of the endemic basket fungus, a bizarre stinkhorn that spits out a white lattice ball that's sometimes seen blowing around like a smelly tumbleweed. It's known by dozens of names among iwi, some identifying its fragrant fruits as the dung of the thunder goddess, Whatitiri.

Mycologist Teresa Lebel likes the basket fungus, but she nominates the even weirder, rarer, seaside version of it.

"It's ... shape ... is almost like a squid, and it often has multiple fruit bodies sitting together, and it's coastal which is totally not like any of the other stinkhorns."

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Myrtle rust has been giving the rusts a bad name lately, so Maj Padamsee, who studies them, nominates one for national fungus.

Mikronegeria fuchsiae is endemic to this country and kindly refrains from murdering its host plant.

Whereas most rusts stick to just one host, M fuchsiae lives on two kinds of native tree, and is a shapeshifter.

A group of scientists from Landcare Research discussed the question over lasagne one night, and came back with their top pick.

It's Cordyceps robertsii, or āwheto, which parasitises the larvae of two native moths and has strong cultural significance.

Landcare's Peter Johnston said the reason it was picked was because it was the first species described from New Zealand.

"And it's a fungus that was used by Māori for dyes for tattooing, so it's been known by humans in New Zealand for as long as humans have been here."

The caterpillar-fungus was burnt to make a black pigment that was then mixed with bird fat to make ink for tā moko. These days, āwheto is pretty hard to find, although pre-colonial Māori had it sussed, collecting it in bulk for trade.

As for the 'all black' mushroom Tylopilus formosus, the scientists are largely against having this as the national fungus - mainly because they object to the description of its colour.

It's actually more of a dark-purple violet.