To the awesome power of three

The untouchable trio. Klein, Karan and Lauren reign supreme in New York fashion. Tamsin Blanchard saw their new collections. Photographs: Sheridan Morley

Ralph Lauren, Calvin Klein and Donna Karan are New York's fashion. Isaac Mizrahi has showbiz pizzazz. Marc Jacobs has street cred. Anna Sui has a few new ideas and a clever way with prints. Miu Miu's Miuccia Prada understands the twentysomething woman and Richard Tyler cuts a neat suit. But no other designer showing in Manhattan comes close to making the slick, to-the-minute, highly polished collections that the golden three showed last week. Admittedly, no other designer has quite so much power and money. Ralph Lauren alone turned over an estimated $4.4bn last year.

New York is not the place to look for the Next Big Thing. Here, the clothes paraded by the new wave of models are just like the clothes that we are already wearing. Anna Sui even told the New York Times that the first half of her show - knitted dresses, jersey tunics and trousers, and plain black jackets - was based on "the way people like to dress right now". However, if you are looking for a good trouser suit, a floor-length cardigan, a suede shirt jacket, an immaculately tailored suit, or the perfect soft, tie-belt, ankle-length coat, then when September comes, book a plane ticket and take an empty suitcase.

There is a contradiction in fashion in that good, wearable clothes often make for boring fashion shows. There was little excitement in the Bryant Park tents last week, bar a few celebrities causing the odd frenzy of camera flash. Donna Karan and Ralph Lauren both chose to leave the tents for their own showrooms, restricting seating space to a bare minimum. Both designers were on form, with Karan presenting streamlined body foundations - stretchy stocking-top catsuits, shirtbodies, suede wrap coats, long zip-front coats in luxurious cashmere and slim maxi skirts.

After the recent dominance of synthetic fabrics, there has been a marked return to soft cashmere, matte jersey, wool crepe, leather and suede. Ralph Lauren made fine fabrics look comfortable. A wide cord Crombie-style coat, bootleg stretch jersey pants, and suede safari jackets all looked effortlessly wearable. Lauren also showed a sharper silhouette, with sharply tailored Savile Row-inspired masculine suits that were cut so close to the body as to make them resolutely feminine.

At Calvin Klein's show the designer's next advertising campaign star, the actress Gwyneth Paltrow, sat and watched the show, no doubt planning her winter wardrobe. She has chosen the right season to work with Calvin. His collection included the most luxurious cashmere and wool velvet coats, trouser suits with softly belted jackets, and a series of jersey geometric colour-block dresses that are the sort of thing that makes getting dressed in the morning as easy as pouring maple syrup over a pancake - although to avoid unsightly lumps and bumps, pancakes would definitely be off the agenda - for the silhouette to strive for next winter is long and lean. Klein is planning to open shops in Bond Street (where he would join Ralph and Donna) and Sloane Street soon. And for once, they will be a happy addition to the High Street, offering clothes that will be an investment and a dream to wear.

The designer offered some of the best knitwear of the week. He calls it "modern sweater dressing" and it needs little explanation but to say that floor-length cardigans, flattering and practical shirt jackets and fine-gauge knitted trouser suits are all you will need to update your wardrobe next winter. There were also plenty of turtle necks, something the New York trade paper Women's Wear Daily has singled out as a major trend for next winter, offering the useful advice that "if you've got a short neck, cut it off. Or make a date with your plastic surgeon. Or just sit this season out."

Marc Jacobs, the darling of New York's fashion clique, showed a collection that mixed the favourite decades of the week, the Twenties and the Seventies. Anna Sui had obviously seen Carrington and was inspired by the Bloomsbury set with cloche hats, sensible knits, window-pane checks and bias-cut print dresses. Taken in isolation, there were some interesting pieces, but wear it head to foot and you will look like an out-take from a BBC period drama.

Miuccia Prada has a keen eye for second-hand clothes. For her accessibly priced Miu Miu line, she has turned to the sort of sensible clothing that would confuse most mothers. A camel-coloured below-the-knee kilt made Kate Moss look bulky and a bit of a frumpy Goody Two-Shoes. Prada says, "Gone are the days of bad, good is in." She calls this look "Neo-traditional chic". And no doubt it will catch on. Miu Miu also reflected another trend - a return to romance. For evening, boudoir slip dresses were finished with a frill around the neck or hem and a bright red ribbon threaded around an empire-line waist. They were worn with schoolgirl tights and heavy patchwork leather ankle-strapped shoes, slavishly remade straight from the Seventies.

Thrift stores and flea markets have become the standard source of inspiration for designers and often, you wonder why they bothered. At DKNY and Richard Tyler, coloured suede coats might have been replicated from East Village Clothing Stores. But the suede is new and clean and there is no risk of unpleasant smells or flea bites and that is what you pay for. It is no secret that designers and their assistants frequent the clothes shops that are also the haunts of students in search of a bargain. It is just remarkable that there is often so little difference between the designer version and the real thing.