They're dirty and full of bugs and puddles, where trees take the place of Lego bricks and frogspawn replaces PlayStations. No wonder children are falling over themselves to get into outdoors nurseries

Over his normal trousers and jumper go a substantial pair of fleece socks. Next, a bright red waterproof jacket with reflective strips. Delighted, he gives her a twirl. Then that has to come off again, to put on the kind of sturdy waterproof dungarees a pre-schooler might wear if they were planning a day's angling. The jacket goes back on top, Hunter wellies on his feet and a smart new All Blacks knitted hat complete the look.

This is Evan's first session at Woodland Outdoor Kindergarten, Glasgow's first forest-based nursery. He will spend the day among the trees of Pollok Park with 16 other three and four-year-olds, climbing on tree stumps, digging holes with a stick, playing on a rope swing and pretending to be one of the Three Little Pigs. Evan already goes to a Montessori nursery two days a week and his mother is confident that a dose of mud and sticks will complement his indoor education. "He's a boisterous wee boy. I'm sure this will be right up his street."

Sending a three-year-old, however thoroughly wrapped up, off to spend a dreich winter day in a wood may not sound like the brightest of ideas. Yet outdoor education is seen as a crucial, and previously ignored, element of the curriculum. "There is increased evidence and both public and political conviction that 'education outdoors' can provide important learning experiences that enable young people to learn in, through and about the natural heritage through first-hand experience," as Scottish Natural Heritage rather clumsily puts it. All nurseries are now being encouraged to take learning outdoors whenever possible.

The idea is not a new one: hearty Germans and Scandinavians have been sending their children to forest kindergartens for 50-odd years. The theory is that spending time outdoors, away from beeping gadgets and lurid plastic toys makes children self-reliant and imaginative. Remove the Lego and the dressing-up corner and they have no choice but to improvise, Dangerous Book for Boys style, with pine cones and stones. They develop practical skills such as climbing trees and building dens and learn how to manage risks and assess danger. They develop stamina and resilience while learning about frogs and toadstools. They stop, pretty quickly, being terrified of getting dirty. It gives them a bit of time off from the 21st century.

There was already a handful of outdoor nurseries in rural areas of Scotland when Alison Latta and her best friend Debbie Simmers opened in Glasgow last October. They started with ten children. Just over a year later, they have 70.

Simmers and Latta, who have been friends since they were five years old, are not fresh-from-the- compost-heap green activists. Their backgrounds are not even in childcare: before wearing wellies for a living Latta was a physiotherapist and Simmers ran a care home. Starting a business together came up over every second glass of wine but somehow they had done nothing about it. Then Simmers was made redundant in 2008, while on maternity leave. When her mother sent her a newspaper clipping about an outdoor nursery she thought: nice idea, utterly unfeasible. It took another glass of wine with Latta to turn it from an impossible dream into a business plan.

Pollok Country Park, with 361 acres of woodland, a large car park and the warm, clean toilets of the Burrell Collection, seemed an ideal location. Their indoor base would be a church hall, a five-minute minibus ride away. They managed to satisfy both the Care Commission, which regulates nurseries, and Pollok Park's managers at Glasgow City Council, that the children would be safe and the park would not be damaged in any way.

Fourteen months later and this is as slick an operation as it is possible to run while wearing waterproof trousers, a down-filled coat and a pair of Muck Boots. (These clompers, designed for agricultural labourers and stable hands, are possibly the least alluring footwear ever invented. They make Dr Marten's look like Christian Louboutin cage boots.) But while the staff might look as if they are off to weed the carrots, they are wired up with walkie-talkies and manage the brain-melting task of strapping 14 pre-schoolers into 14 separate car seats inside a minibus, without tears, tantrums or foul language.

Arriving at Pollok Park, unloading the children is not much quicker. They immediately start rolling around on the grass verge while the staff engage them in a discussion about where today's base camp should be. The nursery moves around, to different spots with names that would have Bear Grylls booking a camera crew: dinosaur tree, monkey tree, training camp, squirrel house, graduation camp ... Some of these have a link with reality: dinosaur tree is near a spiny, upturned monster that looks like a prehistoric skeleton; training camp was the scene of a short-lived craze for physical jerks and star jumps. Others are more fanciful. Glasgow City Council does not allow primates in its outdoor facilities. After some debate, it's the squirrel house, named after a mini-den built for the fluffy-tailed rodents during the summer. "It was," recalls Simmers, "never really used by squirrels but the name stuck."

The children carry matching rucksacks, supplied with the rest of their uniform when they join the nursery. The staff have enormous packs containing all the water, tents, books and emergency supplies needed for the day's activities, plus lunch and drinks. Bella Shaw, who is not tall, straps on one that towers well over her head.

A pack of tiny red-jacketed figures carrying sticks, the children have become a familiar sight in the park. The red makes them easy to spot without jarring – Simmers rejected the idea of high-visability jackets as too garish and unnatural. The children all wear their own hats, which breaks up the uniformity of the group. Today there is a Peppa Pig, a Tunnock's teacake, a pair of teddy bear ears, a grey hunter's hat with skulls and a bright pink hunter's hat with fur trim.

The march to the site takes place at toddler pace, up the side of the Burrell Collection then through the woods to an open clearing. There is a large, uprooted tree with a muddy puddle at the bottom. The ground is thickly covered with fallen leaves, the surrounding trees are bare. And that's it. This will be today's nursery.

The children, none of whom have complained about being cold, tired, bored, unable to walk another step or in desperate need of a quick burst of Cbeebies, immediately start milling around, kicking leaves, taking off rucksacks and gloves, finding a well-chewed dog's ball. The only dissent comes from Finlay, who is hungry, while Iona quietly produces a bottle of warm orange squash, cunningly wrapped in a sock to preserve the heat, and has a long swig.

It is now 10:30am, when most nurseries are giving children a snack. Simmers explains that they push on, set up camp and give the children lunch at 11:30am, when they are ready to eat a good meal. So the staff seamlessly split up.

Graham Fraser, a former sports coach, takes on the role of Big Bad Wolf and a gaggle of little pigs chase him through the trees. Debbie Taylor has yet to join the main camp. She is supervising a sub-group who stopped for an impromptu burst of den-building. This leaves Anneke Ferreira, Shaw and Simmers to string a hammock between two trees, in case any of the little ones needs a nap. They put up a toilet tent and rig up a basic tarpaulin, in case of rain. A bag of books hangs from a broken branch, waiting for the afternoon story session.

The children who are not pursuing Fraser or working on the den are left to their own devices. Blaise, who at five is older than the other children, has constructed a see-saw out of tree bits. He plays on it with poor, starving Finlay, who sings 'See Saw Marjorie Daw' while wobbling up and down. Blaise is home-schooled but his mother thought he would benefit from spending one day a week in the woods with other children.

"We are a very outdoor-oriented family," she says. "When we moved here from the Middle East he went to another nursery but they spent all the time indoors, sitting down, drawing. I think education is all around, it's not sitting down with a piece of paper."

No sooner is the camp established than it is time to get ready for lunch. "Parents worry about it being a long day for their children," says Simmers, "but everything takes so long, time just flies." The pre-meal handwashing ritual, for example, is more of a performance than a Japanese Noh play. Simmers arranges the children's rucksacks into a rough circle while they, having removed their heavy padded gloves, stand in another circle, facing outwards, hands held outwards. Shaw comes round with a canister of water and dispenses a drop to each child. Ferreira follows with a pump dispenser of liquid soap. There is more water, then a round of hand towels. They do all this quietly and efficiently, including newbie Evan. Only when their paws are clean and dry, and they have placed the used towel in a bin bag, do they go and sit down.

"We have hardly any rules," says Simmers, "but we are very strict on handwashing. We encourage them to dig in and get filthy, then wash their hands." These children are hungry. Many of the old-timers put on a thin pair of gloves, called by staff "eating gloves", before packing away soup, sandwiches, flasks of hot pasta, pieces of broccoli ... No one has brought sushi today, although Fraser claims it has happened. He has brought a lunch fit for Giant Haystacks, a supersized Tupperware box of fruit, sandwiches, crisps and juice. Light rations by his usual standards, he explains. While chomping through their provisions – and the children eat at their own pace, which in some cases is slower-than-snail – the conversation ping-pongs around. Meanwhile Evan, who has been gamely working on his sandwiches, has started to wail. His feet are sore. Taylor, who has been sitting beside him, scoops him on to her knee and gives him a cuddle, while Shaw roots in the bottom of a rucksack for a pair of heated pads, Taylor whips off his wellies, rubs his feet, pops in the hot pouches and gets the boots back on.

This is not uncommon, says Simmers, for new children. It can take a couple of days outside to acclimatise to a day of damp earth underfoot.

When she started, Simmers thought the biggest problem would be persuading parents to send their children. Not the case. The cost, 39 a day, is comparable with other private nurseries. A Care Commission report marks Woodland Outdoor Kindergarten as one of the best in Glasgow and there is now a waiting list. The hardest thing has been to find staff who are as mature, resilient and chill-resistant as the children.

"We did a round of recruitment in the summer," recalls Simmers. "We brought all the candidates to spend time with the kids in the woods and set up a tarpaulin with three camping chairs and our clipboards. That was where we did the interviews." This made it immediately clear who was suitable for the job and who would go running back to carpet and central heating-land without a backwards glance.

"Some were so uncomfortable. There were wasps and midges and they would be jumping out of their seats and slapping their legs. It was a hot day and some came along wearing little vest tops – but it gets cold in the forest."

The current staff combine a range of academic qualifications with outdoor savvy, knot-tying prowess and the ability to give a wee boy with cold feet a big hug. Shaw, who is Norwegian, grew up in the forest "with elk running around". She went to an outdoor kindergarten as a child and trained in Oslo.

There is more daylight in Scotland. Otherwise, not so many differences.

"Kids are kids regardless," she says. "They love sticks, stones, bugs, collecting things to take home for mummy and daddy. They love being muddy." A Norwegian outdoor nursery would have more men on the staff – "they are all around 50-50", and there would be more drama and stories about trolls. The weather, although much colder, is easier than the Scottish climate. "Here I'm always cold, with the wind and the damp. I am wearing three layers of thermals."

Ruaridh, one of the youngest children, is not yet three. He is stolidly working his way through his sandwiches while the others have wandered off to play on a rope swing knocked up by Shaw, or inspect some fungus in a rotten tree root.

There is a muddy puddle nearby, which is also of great interest. Evan's foot

pads have done the trick and he is watching the bigger children on the rope swing with wide eyes.

"They have a great burst of energy after lunch, so that's when we go for a walk or an adventure," says Simmers. Then, about 2:30pm, we have our snack, talk about the day and have a story."

There is a curriculum subject every week – this one's is weather – so the staff guide the conversation towards whatever has been bothering the barometer. After that it is time to take down the tents and head back to the church hall and waiting parents.

"I expected she would be tired at the end of the day," says Olivia's mother. "But when we get her back down she is running around." Olivia, aged four, started spending two days a week in the woods but liked it so much it went up to three, then four. "When she went to another nursery she was quite shy and subdued. Here, she is really confident and lively with tons of energy." Her mother smiles wistfully. "I spend all day in an air-conditioned building. I wish I could be outside too." n

www.woodlandoutdoorkindergartens.co.uk

This article was first published in the Scotland on Sunday on December 5, 2010