Kenneth D. Cochran, Secrest Arboretum of The Ohio State University Ohio Agricultural Research and Development Center, Wooster, Ohio; and James A. Chatfield, Ohio State University Extension, Northeast District and Department of Horticulture and Crop Science.
North, South, East, or West, in all except a few states, holly can be grown. Even a Northerner can grow hollies with certain species and cultivars surviving in habitats or under environmental extremes and stresses of moisture and temperature. Broadleaved evergreen hollies growing in cold winter climates are positioned for optimal growth and development if planted in a microclimate. Strong drying winds, coupled with temperatures below zero degrees Fahrenheit and a lack of snow cover, cause more rapid desiccation of leaves in open locations than in microclimates.
There is probably as much damage from desiccation as there is from freezing. Plants exposed to winter sun, plants deprived of nutrients, and even plants with unprecedented heavy fruit set previous to a cold winter could accentuate the final winter injury. Until a plant has a deep root system, winter injury may result. The water loss in broadleaved evergreens from drying winter winds and the combination of deep frozen soil and a lack of mulch may result in massive top damage if not outright winter kill. This is especially true when a plant has a southern exposure.
Microclimates are uniform local climates of a small area or habitat that gives plants relief from the brightest and warmest portion of the day and from strong wind-swept exposures that tend to increase foliage desiccation and thus produce stress conditions for the plant. The east side of a building or an east-facing shelter of plants is an ideal microclimate for hollies, particularly if it receives sun before the heat of the day.
Try the plant — even if it is marginally cold hardy — and be willing to take a chance. Take the time to maximize cultural care and enjoy it as long as it lasts. And if it dies, try it again, in fact, give it three tries before it's out!
Remember the words of Peter Smithers, who said: "I consider every plant hardy until I have killed it myself."