Fruit doesn't just come from a supermarket. It actually grows on trees and bushes and stuff. And some of those trees and bushes and stuff in Hamilton are on public land that you can pick yourself.

Free food, in other words. And food untouched by modern chemicals, processes, hands, even taxes. Touched by nothing but nature.

How cool's that?

ETHAN WELTY/FALLING FRUIT Caleb Phillips, left, and Jeff Wanner pick mulberries from trees in Boulder, Colorado.

Yeah, there's a whole subset of people who are already doing this, and they're not the hippie types you might think. Even grandmothers are at it.

READ MORE: Fruit foraging in Christchurch's red zone

If you do a quick Facebook search for "fruit tree", you'll find plenty of requests from people looking to take extra produce off your trees if you're, say, buried in feijoas or grapefruit. But you can also hunt the free free stuff, open to anyone who passes by. And so we found a map, to do just that.

KELLY HODEL / FAIRFAX NZ Jack Strange picked fruit to earn money to buy a Lego crane.

Now, this map was created from a list provided by Hamilton City Council and various other sources. It is incomplete. And some of it's probably out of date - like, maybe, this crabapple tree has been yanked out or died or something. But the free map is interactive, sort of like Wikipedia, so anyone can update it (and we're relying on community policing here).

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Mapping publicly accessible fruits and vegetables is nothing new. American Caleb Phillips has been doing it on his website, Falling Fruit, since 2008.

ETHAN WELTY / FALLING FRUIT Urban foraging taps into our hunter-gatherer instincts, says Maxine Fraser.

But what started as a hobby in Boulder, Colorado, grew into a worldwide obsession. Phillips reports the not-for-profit website and mobile app has 8152 registered users and many thousands of anonymous users who have mapped 1.4 million trees around the world.

"I was out picking pie cherries on the college campus where I was going to school and some students walked up to me and warned me about eating these potentially poisonous berries. I was a little taken aback that folks didn't know what pie [sour] cherries looked like, or what cherries looked like growing on a tree."

So he started mapping the fruit trees all over campus, then all over Boulder, then Denver, the state's largest city.

KELLY HODEL / FAIRFAX NZ Rhode Street School principal Shane Ngatai is working with the Avis Leeson Fruit Tree Trust to put 10,000 fruit trees in schoolgrounds around the Waikato.

"And then I was in Hamilton on a National Science Foundation fellowship working with the University of Waikato. So I was mapping trees in Hamilton, too.

"I would go on this big run around one of the pastures and I would just take my shirt off after the run and just fill it with oranges. I also fell in love with your tamarillos."

He found kiwifruit, oranges, feijoas, all on public land in Hamilton, the third city on his map.

FAIRFAX NZ Maxine Fraser from the Waikato Tree Crops Association is an avid forager, but doesn't limit herself to fruit and nut trees.

And that's how it stayed until Phillips met another urban forager and together they extended the site worldwide.

In March 2013, the pair launched the North America version of Falling Fruit.

They quickly started hearing from people in Poland, Israel and South America who wanted to extend the map to their cities.

"When we designed it, we tried to think of Wikipedia, the notion of a public resource, open data, open source.

"We wanted it to be a common resource that anyone can use, so you can create an account and keep track of the things you have added, or you can just use it totally anonymously."

It relies on users maintaining and curating the site as it grows, to notice if a mapped tree is no longer there or has stopped producing fruit or a new one has sprouted.

But the application is more than just a map. Photos of the trees and their fruits can be uploaded, with links to information about the tree and ideas of what to do with the goods it produces.

"I think it's exciting to learn about the different things. For me, the website is a lot of fun, but it's also about education. It's about reminding folks that food is something that grows all around us, something that you can grow yourself in your garden.

"It's not just something that exists on grocery store shelves. It's reconnecting people to the food that grows all around them."

The app, however, costs money, although the desktop version is free to use. So we found something free and - no offence, Caleb - a little more locally focused using Google My Maps.

For Hamilton schoolteacher Jamie Strange, foraging is a family affair.

Recently, when his eight-year-old son wanted a Lego set, Strange helped him gather and sell fruit and kindling until he'd saved up enough to buy it himself.

"He had been saving up his money for the term and he had around $40. But the Lego crane was $175. He burst into tears in the shop - he loves his Lego.

"So we spoke to him and said we would help him reach his goal and over the holiday period, we helped him sell a few things."

Jack and his dad picked unwanted fruit from friends' backyards - with permission, of course - and sold it on a stall in front of their home.

"He had some apples given to him, we got some feijoas from friends and we got some fruit pallets and they got sold as kindling.

"He got to his goal and was able to purchase his crane. It's a really good life lesson for him."

It took Jack a week and a half to earn his toy.

Now Jamie's second child, six-year-old Brooklyn, is selling the 12kg of feijoas that they picked from the ground off a neighbour's property. The homeowner was more than happy to have the fruit taken away for free.

And Jamie is not the only one to see the benefits of children picking their own fruit. Schools across the Waikato are getting fruit trees in their playgrounds thanks to the Avis Leeson Fruit Tree Trust, run by Rhode Street School principal Shane Ngatai.

"We gifted just under 700 fruit trees to schools, early childhood centres and marae around the Hamilton-Waikato area. We've got, roughly, around 10,000 trees to give away over the next five years.

"Our vision is, if we put enough fruit trees in every school, in five years we will be producing enough fruit to have a surplus and we won't need to rely on programmes like Fruit in Schools, which the government funds at the moment to the tune of about $4 million across the country."

Alongside gardening, the kids are getting taught how to preserve the food so they can still eat it off season.

"We're providing a sustainable model where children learn the value of looking after something, nurturing it and growing it, to receive the fruit in return.

"If you grow your own food, you won't waste it."

His school has 140 fruit trees on site that have been there for 10 years. Shane said there is enough fruit to supply the community and students with chutneys, jams and spreads.

The surplus is shared around the community, helping those who struggle to pay for their five-a-day.

"People are not going to spend $8 on a kilo of feijoas and they're not fresh. They're going to spend it on bread, milk and eggs. We've got 14 feijoa trees in our school, more than we can eat. We're giving it away to the neighbours.

"So you're teaching the children that if they've nurtured it and it's provided something back to them. They can feed that forward on to other people. They get to meet their neighbours by knocking on their door to share it with them."

The trust was inspired by 86-year-old Avis Leeson, who used to visit 80 schools a year gifting trees she had paid for before ill-health slowed her down.

Now the trust is carrying on her work, but doing it on steroids.

"Last year, we gave pear trees. This year, we're looking at doing plums, next year we will do apples and then we will do citrus. So we are creating an orchard that provides food for nine months of the year - it doesn't all come at once. And because schools are closed over the summer period, there is no waste. Those trees are still ripening."

But if you need some moral support before you head out on that treasure hunt, there's a private Kiwi Facebook group you can join. New Zealand Food Foraging has 1714 members who share knowledge about edibles picked up around the country, plus they share ideas for what to do with it all. They have their own code of conduct, these urban foragers, making sure to only take what they need and not one berry more.

But it's not just fruit and nuts people can harvest. Maxine Fraser has been foraging for the 30 years she's lived in Hamilton and weeds are one of her top crops.

"Two things to bear in mind. You've got to be absolutely sure you're not collecting things that have been sprayed or polluted by passing cars."

If it's on the edge of a road or public park, excluding fruit trees, Maxine says to avoid it.

"You do need to learn your weeds, because some of them are poisonous, and others a lovely when you add them to a salad. And if it's a plant or fungus, you need to identify it positively."

It's always worth researching the plants, she said, because some plants that you might think are a nuisance could be beautiful to eat.

"In Hamilton's gullies, there are wild walnuts - or Japanese walnuts. And the city council gets fed up with these wild walnuts. I just thought they were terrible things, but I looked it up on the internet and it has a sweet edible nut.

"They're falling right now and I got a whole box full of these dropped nuts. I opened them up and they're delicious. So that's a wasted food resource."

She recommends novices read Michael Daly's book, Find It, Eat It.

"It's all the rage, foraging is. I drill into the psychology of it and before we became civilised people, we were hunter-gatherers. It's getting out into the wild and connecting with nature.

"It's also about getting things for free, which is always exciting. And it's an adventure."

But if the wilds of nature aren't your thing, there's a share table on Claude Street where people drop their extra produce for others to pick up. Farmer markets are another step in between harvesting and buying at the supermarket.

"By the time the fruit gets to the supermarket, where you buy it, it's already used up a lot of energy just getting there, as far as the Earth is concerned: lots of fossil fuels, people's time, truck drivers.

"What's the history of this apple I'm about to eat? It didn't just magically appear in the supermarket.

"Foraging is fresh stuff and there is no ecological footprint at all. It fell off the tree and you eat it. It hasn't been through all those stages that are a burden on the Earth."

So go out and harvest. Apples are ripening now, along with walnuts.