Almost daily, I run across this major point of gardening confusion. I was listening to a gardening talk show recently and a caller said they purchased a plant at a nursery and the plant tag said “hardy to zone 9” on it and they asked the nursery personnel what that meant and the nursery was unable to tell them. The experts on the gardening show decried this lack of basic knowledge at the nursery and then proceeded to answer the question incorrectly. In horticulture, hardy means only one thing: resistance to or tolerance of cold temperatures. So, hardy to a particular zone only refers to a plant’s ability to withstand the lowest temperatures in different geographic areas, as determined by the USDA. Hardiness doesn’t address ability to withstand heat, wind, soil, snow cover, or a bunch of other variables. It is possible that a plant could be hardy to zone 9, but not perform that well in zone 9. Hardy is a very specific term, only relating to cold tolerance.
Many times gardeners and potential gardeners ask me if a plant is hardy, which, in horticultural terms, means will it tolerate cold? But, what they really want to know is will it tolerate heat/cold, is it soil-fussy, is it subject to pests and disease and is it easy to keep it healthy? They want to know about heartiness, not hardiness. It might seem like an unimportant semantic distinction, but it is important because horticultural literature uses “hardy” to convey specific information about cold tolerance only, which is of huge importance, but you might think you are getting information about general heartiness. So remember, hardy doesn’t mean hearty, but hearty means hardy. Now, go forth and plant with a clear mind!