Cutting-edge patterns: Orla Kiely's unique designs have made her interiors label a massive global brand

The designer tells Kate Burt why we should all put a bit of colour back in our lives.

The minimalist 1990s. Not a decade that evokes memories of exciting interiors. Or, as Orla Kiely describes it in her recent book, Pattern, a time when colour and pattern "almost disappeared from our homes", while "neutral, natural or monochrome palettes reigned supreme in the form of pure white walls, pale hardwood or stone floors, glass and stainless steel".

This was also the period when the Dublin-born designer, whose name has since become a byword for colour and pattern, went from being an up-and-coming hat designer to an instantly recognisable brand, thanks largely to what has become her trademark print, the retro-tinged "Stem" graphic, now found on everything from mugs to cushions, notebooks and even cars (look out for the new Citroë* DS3).

So how did Kiely, who heads her business with her husband, Dermott Rowan, pioneer a style that was then so unfashionable? "We weren't about over-designing or over-embellishing," she says. "Everything was quite clean and simple. So in a way [the designs] were actually very minimal. They just had a great big pattern all over them." And it's true. Take a second look at an Orla Kiely motif and, while it might evoke an age of garish Formica, psychedelic swirls or a bit too much brown – the Fifties, Sixties and Seventies are big influences – what it takes from those times is cleverly distilled into something stylised, tasteful and clear of twee nostalgia.

Orla Kiely's first degree course, at Dublin's National College of Art and Design, was in Print for Fashion, but her first job was with a wallpaper and fabric designer in New York. It was the mid-Eighties, before digital design, and colours had to be mixed in gouache, by hand, painted on to strips of card and dried with a hairdryer before they could be presented to the boss. Once approved, they'd have patterns hand-painted on to them with tiny brushes, which would be copied and pasted until a sufficient repeat emerged and the design could be looked at from a distance to see if it was working. Kiely says the process gave her "the best colour training anyone could have had", and remembers that some of the most frequent comments from her boss were "not dirty enough", "add linden green", and "make it cleaner". They resonated with the apprentice, whose earthy tones would become the backbone of her designs.

But it was the Ireland of her childhood in the Sixties and Seventies that first inspired her. "It was lovely," she says, "the greens, the yellows ... the clouds, the skies and the sea. In a sense, it's not colourful, but you do see accents in the wild flowers by the road, or the yellow gorse on the mountains. I love all those dirty colours – and mixed in with sharp brights they look more sophisticated."

Her parallel taste for the domestic vintage styles echoed in her prints developed early too, helped by her mother's kitsch kitchen: olive green Formica cupboards and a gloss orange ceiling. "You'd never do that now, but I remember at the time thinking it was quite cool. I still like the idea of a mad ceiling." There was also a passion for knitting and for crocheting multicoloured waistcoats, "inflicted" on her younger sister.

Back in London, after working for the fashion company Esprit, she took an MA in knitwear at the Royal College. Which is where the hats came in. A buyer from Harrods had been at the degree show and liked her designs.

A year or two later she made a significant change of direction. While visiting her "tiny stand" at London Fashion Week, Kiely's father observed that no one was wearing hats – but everyone had a bag. Starting up any type of business, Kiely says, requires "hard work, a steep learning curve and an element of luck". This moment, perhaps, was the latter of those three, as it was via the bags she went on to develop that Kiely's distinctive prints first hit the public consciousness.

The next lightbulb moment – after her printed fabric bags had made an impact in the "sea of monochrome" in the late Nineties – was the idea of laminated cloth. "At the time," she explains, "no one was doing anything like it. Laminated fabric, in those days, meant tablecloths."

It meant her print designs could be more prolific as she was able to create them all year round. Stem's imminent status as the Kiely trademark was cemented as it got its first of the many makeovers which have helped it to become so popular: this time, its first wintery colourway. "It's very flexible," she reflects of the design. "We've been able to adapt it, modify it, rescale it, recolour it, add texture ... It's also quite clean and unfussy – and interestingly, perhaps because of that, is also not off-putting to men." The bags and their best-selling pattern were fresh and unique. They took off. Since then, every Kiely collection has featured a version of Stem.

The ubiquitous graphic, of course is just one strand of Kiely's textile design. But it is far from her only familiar print: cars, apples and pears, martians, glass tumblers, acorn cups – without even looking, you've almost certainly seen them all, whether printed on furniture in Heals, bedding at John Lewis or toiletries bags in giftshops nationwide – not forgetting fashion, which Kiely is still passionate about (she has just opened a dedicated new shop in the King's Road).

Aside from her childhood, Kiely takes inspiration from the geometry she sees in nature; a kitchen shelf full of mid-century cups and saucers, vintage fabrics by designers such as Lucienne Day and the less famous Barbara Brown, who designed textiles for Heals in the Sixties and Seventies, as well as anonymous charity shop or accidental finds. As a student in rented flats, she says she used to "love opening a cupboard to discover layers of old patterned wallpaper inside". In Tokyo she snapped rows of bicycles and twisted concrete flyovers for her moodboards, while this year's spring/summer collection was inspired by the Cornish paintings of Patrick Heron. And these things get translated – cleaned up, transformed, repeated – and become, eventually, a Kiely design. "I sometimes think that my brain works in repeat," she writes in Pattern, "I love the order and regiment of repetition and how everything can be patterned in this way, as if you are looking at the world through a prism or kaleidoscope."

Easy for her to say. But not necessarily an easy look to incorporate into the home. How does she advise the pattern-shy and colour-phobic to be bold? "I always think it's good to plan one strong feature rather than lots of bitty things," she says. "So if you're going to go for patterned wallpaper, you don't really want print on your sofa and print on your floor: make it a focal point. There's less opportunity to get it wrong."

"I actually think brown is a very sophisticated colour; cool and very strong. It's a great base for colour – if you have brown walls then it's nice to have colour in other places – a yellow chair or a kingfisher blue sofa. It's what you put with it," she continues. That said, there are certain colours she would never combine: "Purple and pink. Purple's not a big colour for me anyway," she says, "but I'd combine it with brown. When I'm doing colour, I tend to work in families rather than opposites. For example, red is lovely with soft pink; ochre is lovely with yellow, and so on."

Take inspiration from your accessories too, she suggests. One of her favourite photographs is an atmospheric shot taken for the French fashion house Courrèges in 1970 – of the back view of a girl on an orange spacehopper, bouncing past an old Renault van on an otherwise deserted road. "Treat photos and objects as pattern," she says. "You need to plan what goes with it and so many people go for white, perhaps because of that – but you don't have to. Not if you look at the colours in the artwork."

Are there rules? In her book she goes in some detail into the mathematical proponents of pattern, and Isaac Newton's theories of colour. "It's interesting to be aware of that," she says. "Theory is all very well – but I like to break the rules." Again, easy for her to say. Are there ways that those less confident and experienced can practise? "Looking at paintings is always good," she says. We do that for our collections and it can be quite surprising. There's a Danish painter, Per Kirkeby, who's a good example. His colours are beautiful – and there's always a surprise, something completely strange in the corner. It's a great way to study colour."

What about pattern itself – where does one begin to mix and match? "Different scales are good, different coverage is good," she says, explaining that the idea of "clashing" is the point, rather than the thing to avoid. "They kind of need to contrast – you want to link the colours somehow, but if you put similar patterns together, ones with the same weight, for example, the risk is that it can look like a mistake." But, she adds, it's also personal. "One person will make it work. Another won't."

Even so, people shouldn't be so scared of pattern in the home. "You just have to go for it. That really is the point. Just be brave."

Pattern by Orla Kiely is published by Octopus Books (£25). To order a copy for the special price of £21 (free P&P) call Independent Books Direct on 08430 600 030, or visit www.independentbooksdirect.co.uk

A coward's guide to pattern

* Less is more – make it a focal point rather than going mad

* Don't assume brown is drab – it's a great base

* Try working with a family of colours, rather than opposites

* Rather than having a white backdrop, work with the colours in a favourite painting or object

* Link patterns by colour, but mix and match scale, coverage and weight to make it look deliberate