Colour their world: in their celebrated garden and nursery ... transplanted Canadians Sandra and Nori Pope are revolutionizing the one-colour border.

IT WAS POURING RAIN LAST MAY WHEN WE VISITED SANDRA AND Nori Pope's garden and nursery at Hadspen House in Somerset in southwest England. Wet weather had alternated with brief flashes of sunshine all week as my husband and I toured as many famous gardens as we could fit in. But on this day, the rain wouldn't let up.

We'd heard that the Popes were a transplanted Canadian couple who were making a splash with monochromatic borders that showcased colour in an extraordinary way. They had become renowned--in England, of all places, a country full of exceptional gardens and gardeners. What's more, Hadspen Garden and Nursery, where they settled, has an impeccable horticultural pedigree. Penelope Hobhouse, the doyenne of English garden design, gardened there for 12 years, working closely with nurseryman Eric Smith, a well-known plant breeder whose name is linked to choice hosta cultivars grown around the world. …