The world might feel a little post-apocalyptic right now, but according to food writer Olia Hercules, come summer, the landscapes of Ukraine can look pretty post-apocalyptic anyway – but for another reason: Watermelons. Fields of them.

"When they're fully ripe, you can't really see how they're connected to the ground," she explains. "It just looks like a huge field with these beach balls; this really weird barren earth, and then these big green giants. They can grow up to 20kg where I'm from."

Hercules, 36, was born in the south of Ukraine, growing up in Kakhovka before moving to Cyprus and later England, where she studied at Leiths cookery school and worked for Ottolenghi. Her new cookbook, Summer Kitchens, celebrates the food of those long, hot Ukrainian summers, and the structures in which they were – and are – often cooked.

Traditionally, young couples would fashion temporary homes to use while they built their life – their main house, allotment and orchard. It would then become their 'summer kitchen'; a space to cook and preserve when the weather grew sweltering.

Now London-based, mentioning such kitchens to friends in Britain, Hercules realised they were a little-known phenomenon outside of Ukraine. But inside Ukraine, despite its vastness, despite the echoes of many different cultures and cuisines, and despite the different materials used to build them, "everybody's got a summer kitchen". They're "a really nice way to look at how Ukraine is very diverse but also very united," says Hercules.

Flicking through the pictures in the cookbook, there's definitely a rough, other-era charm to the kitchens. Hercules retells a story her mother told her, about her grandfather and a yellow cherry tree that was in exactly the perfect spot for his summer kitchen. "He just couldn't bring himself to cut this really prominent, heavy branch off, so he just incorporated it," says Hercules. "It came into the wall and came out of the ceiling. I just thought that was a bit of magic, and also just sensitivity and respect for nature."

Childhood memories often have a golden glow of summer to them, but Hercules' recollections of her Ukrainian summers, and what she ate, are more rural and aglow than most. "[It was] really nice waking up in the morning, running across the yard to the kitchen. There'd be a massive bowl of homegrown strawberries there, nature's sweets, really small intensely sweet ones," she says, while her grandmother, who had masses of raspberry bushes, would "have this massive cauldron on the stove, and she'd be cooking this really runny, almost raspberry compote. The sugary froth that would collect on top, she would skim that off and give it to us in bowls to eat – people so often say it's scum, but it's not, it's just air bubbles, sugar and bits of raspberry; it was delicious."

Raspberry froth doesn't make it into the book, instead there are soothing bowls of fish broth with dill to recreate, sourdough loaves for beginners, crisp cauliflower fritters, sour cabbage leaf rolls and pigs' ears with garlic to try.

Hercules also goes big on fermenting, pickling and preserving everything from chillies to those dystopian watermelons. "We have a special word for it, which means just to 'make things sour'," she explains, noting how fermentation is so ingrained in Ukrainian cooking that the science of it isn't even really considered, despite its sudden trendiness elsewhere. "My parents, my grandparents, didn't even know about the health benefits, to be honest with you," she says. "It was just a tradition and something we did. And we love the flavour of fizzy fermented tomatoes just popping in your mouth."

Pickling, which was usually done in summer kitchens during September, provided a way to make the best of a glut of fruit or veg – be it dill pickles or cherries – and ensure the crunch and freshness of summer would be available in some form or other come winter, "even though it was a little bit salty and a little bit sour.

"[People] have cellars, sometimes underneath the summer kitchens or nearby, and you go into any of these cellars now and they're just stacked with jars and jars and jars of all of this produce," notes Hercules, "which will keep there for a year or two, or even longer."

It's just one of many practices considered so everyday in Ukraine, that on research trips home, Hercules would say to people: "'Can you tell me about this recipe?' And they're like, 'Why would you want to know about this? It's such a normal and ordinary thing.' I think people lose sight of having this richness.

"Having 40kg excess of organic, beautiful aubergines – to me, that's treasure," she continues. "It's such a wonderful, magical thing still, but I don't know if people in Ukraine necessarily see that."

Those 40kg of perfectly plump, mulberry-coloured fruits she mentions were a glut her aunt dealt with by dropping sacks of them outside Hercules' cousin's house. "Just like, 'There you go!'," she says with a laugh. "[My cousin] was like, 'I've got two children! I've got a job! What the hell! Am I gonna ferment 40 kilos of bloody aubergines?!'

"The younger generation is becoming a little bit indignant about some traditions," she muses. "I don't know if there's less time or there's just more distractions, but eventually, after the little jokey argument they had, she did ferment them – I think she returned 20kg.

"The world is changing, but hopefully maybe this [pandemic] will be a pause, and then we'll go, 'Actually, wait a minute, maybe there's something to those traditional ways'," she adds thoughtfully.

"If we have these moments of, 'Oh, I don't know what's going to happen. I don't know if I'm going to have enough fresh produce', maybe it is worth growing all of those aubergines and preserving them for a rainy day. Maybe people will stop and think and not totally abandon that."

It's just a case of having enough jars, and that particular taste for sourness. A summer kitchen of your own wouldn't be too bad either – we can dream.

l Summer Kitchens by Olia Hercules is published by Bloomsbury, priced £26.