Temperature Measurements, Survival, and Growth of Container-grown Ornamentals, Overwintered Unprotected, in Nursery Shelters and under Microfoam Thermo-blankets1

Ilex crenata Thumb. (Japanese holly), Buxus sempervirens L. (American boxwood), Prunus laurocerasus L. (cherry laurel) and Cotoneaster congestus Bak. (dense cotoneaster) plants overwintered under the microfoam thermo-blanket survived the winter of 1976-77 better and grew larger the following growing season than plants stored unprotected or overwintered in shall shelters covered with white poly. Irrigating plants at 3 week intervals in shelters during winter storage did not improve plant survival. Plants stored unprotected suffered the greatest amount of winter injury. Soil temperatures under the microfoam thermo-blanket were consistently higher during the coldest part of winter than in all other treatments. Air temperatures under the thermo-blanket fluctuated the least initially until mid-February, but began to fluctuate more as days grew longer and ambient air temperature increased in late winter.