Surprising scientists and horticulturalists, once-mild downy mildew disease has struck the popular blooms in 33 states
A puzzling plant disease may dethrone one of the most popular and reliable flowerbed plants in North America, the garden impatiens.
A relatively benign condition known as impatiens downy mildew has recently turned ugly, for reasons under debate. For decades, U.S. gardeners rarely noticed downy mildew on their impatiens. But in the last two years, the disease has ravaged flower beds in some of the more humid parts of the country. After rain or fog followed by balmy nights, the disease can turn a lush flower border into a straggle of bare stalks that eventually collapse and die.