Connel said his seminar at last week's Chicago Independent Garden Center Show proves that although "the US invented Christmas" the UK's "less is more" merchandising was the best in garden centres worldwide.
He said: "Consumers are being overwhelmed by choice. They are looking for the retailer to help them navigate. The UK has shown the US it is possible to take a more disciplined approach."
Connel said Garsons Farm in Esher, Surrey, for example, was "clean, commercial, shoppable and inspiring", and puts customers at ease because they have confidence that the retailer is in control.
He added that Homebase and B&Q had limited Christmas themes to around six - while some independent garden centres still had up to 80 - and that the UK was also ahead of the US in grow-your-own.
The "welly to belly" market is hot in the US, he said, but UK garden centre displays of kitchen gardening and potato bags were more innovative.
Garden designer Diarmuid Gavin, Jim Bradley from Mid Ulster Garden Centre and garden centre architect Gary Wilburn were also among the UK and Ireland contingent.
Connel added that he spent a day at Matterhorn Nursery in New York state, where a wine-tasting bar for local tipples impressed him.
He added that Pennsylvania centre Terrain at Styler's met the "emotional merchandising" benchmark that all UK centres should seek to achieve. The "garden-inspired lifestyle store" appeals to women and Generation X through its appeal to well-being.
The show attracted 3,267 buyers from 2,000 stores.
Show organiser Jeff Morey said demand for exhibitor space was 160 per cent of the size of last year's inaugural show.
Next year's Independent Garden Center Show returns to Chicago's Navy Pier on 18-20 August 2009.