I wasn’t sure what to expect from an autumn trip to Finland, my first ever to the country, but spending an afternoon sprawled on a deck chair beneath blazing blue skies certainly wasn’t part of it. After a morning walking beneath the leafy canopy at the Mustila Arboretum – the oldest, most extensive botanical garden in the country – and a lunchtime wine-tasting (more of which later), my friend Sara and I pitched up at the Sahanlahti resort, deep in the Finnish Lakeland, only to find sun-drenched scenery that felt far more Mediterranean than Nordic.

Sahanlahti was the second stop on a mid-September road trip from Helsinki to the shores of Lake Saimaa; a journey in search of ruska, the spectacular autumn colours that blaze for a few short weeks before the long Finnish winter sets in. However, on our opening drive east from the airport to the Radalla resort, set on Lake Urajärvi, most of the thousands of trees we drove past were resolutely green, with just the very tips of the leaves tinged with auburn, like a foliage balayage.

“You’re too early,” the waitress told us, cheerfully, after we had checked in to our chic waterfront cabins, and were tucking into hefty plates of crispy garlic chicken, scattered with freshly picked chanterelles, in Radalla’s quiet dining room. “But you might get some sun tomorrow.” Later, walking back to our cabins through thick drizzle, we agreed she was most probably just being kind.

The Radalla resort is just one of dozens of lakeside hotels scattered across southern Finland – many with self-catering cabins, sauna complexes and gleaming metal steps that lead from wooden piers down into the chilly waters of the lake. The grey drizzle we awoke to made a dip less than appealing, and instead we decided to set off for our next stop, taking in the arboretum en route before finding a place for lunch.

Driving in southern Finland turned out to be quite different from other countries. Most settlements fringe the lakesides, so they tend to be tucked away down side roads leading off from the main highway. Instead, trees – those resolutely green trees – rolled past us for mile after mile, until slowly the fields began to melt into lakes, one after another, the road snaking alongside the blue-grey waters, or stitching together small islets that lay scattered between them.

Googling somewhere for lunch, Sara came across the Ollinmäki winery, an unexpected find in a country that grows absolutely no grapes. Instead, berry wines are hugely popular, and once settled in at our table, we were persuaded to try a flight of six, accompanied by a bowl of hearty elk soup (which tasted considerably better than it looked) and a leaf salad with local cheese. One wine, the white currant and berry Myllärin Matti was particularly delicious, with the tang of a crisp sauvignon – although I wouldn’t want to find out what a Finnish hangover feels like.

From the winery it was an easy drive to Sahanlahti, by which time the weather had cleared and pin-sharp blue skies gleamed above the shores of Lake Saimaa. The main house – painted butterscotch-yellow and dating back to the mid-18th century, when the owners presided over the local sawmill – had a languidly old-fashioned air, but dinner at the Koskivahti restaurant was anything but: rich mushroom soup, slivers of goose confit with lingonberry sauce, wafer-thin beetroot carpaccio with tangy goat’s cheese.

It might have been too early for the leaves to turn, but we had arrived right in the middle of harvest season, when heading out into the fields and islands to pick wild mushrooms and berries (of which there are 35 different varieties) is practically a national sport. We had barely set down our bags at our final stop, Järvisydän resort, before we were whizzing out across Saimaa on a small motor boat, baskets tucked between our feet, to hunt for chanterelles and look for rare ringed seals and ospreys.

The sky was flawlessly blue as we whipped across the water, disembarking first to pick the mushrooms – slashes of bright yellow among the green undergrowth. We were guided in our harvesting by Sebastian, the 12th generation of the Heiskanen family to be running Järvisydän. “Back in 1654,” he told us, “my family were given a portion of land by the Russian tsar, to build a tavern on the route between St Petersburg and Helsinki.” More than 350 years later, the tavern has morphed into a 100-room resort, offering everything from starkly modern glass-walled cabins, high in the forest, to hexagonal log houses with bedrooms set off a central, fire-lit atrium, and camping pods.

It’s an extraordinary place: everything – from the vast reception, dwarfed by a replica Viking longship hull hung above reception, to the restaurants, bar and the Hobbit-like spa – is built entirely from local stone and timber. A visit to the spa seemed the perfect way to warm up after our chilly boat trip, with six different saunas to dip into – although the “sunken log” sauna, where the temperature reached 70C, gave me some sense of how an ice-cream might feel if left out in the sun.

Of the three resorts we visited, Järvisydän was the standout – for its history, for the spectacular scenery of Lake Saimaa that surrounds it, for the delicious mushroom soup and for the long, sunlit walk we took on our final afternoon, through the dense pine forest, where red squirrels skittered around in the branches above. It was a wrench to leave on our last morning, but as we sped back along quiet roads to Helsinki, we agreed Finland had – in spite of our foliage fail – outstripped our expectations. It was more beautiful, more peaceful, more sunkissed than we could ever have imagined.

Ruska (the vibrant colours of autumn foliage) begins in the north of the country in early to mid-September, reaching the Lake Saimaa region in the south by early October.

The trip was provided by Discover the World. A four-night bespoke self-drive trip staying at Radalla, Sahanlahti and Järvisydän resorts starts at £794pp, including B&B and car hire, but not flights.