Zone 4

• Zone 4 temperatures reach annual average lows of minus 30 degrees Fahrenheit. The Korean boxwood (B. microphylla var. koreana) is cold-hardy to Zone 4. This evergreen grows slowly to 3 feet tall and has leathery, pungent foliage that turns yellow-green to brown in the winter. The "Winter Beauty" cultivar has bronze winter foliage. Plant Korean boxwood in full sun to light shade and cool, moist soil. The "Green Ice" variety (B. sinica var. insularis "Green Ice") is cold-hardy to Zone 4. This compact boxwood grows to 3 feet tall with an equal spread. Its new foliage is blue-green and matures to a lustrous deep green. Green Ice prefers full sun to partial shade and moist, well-drained soil.
  
  

Zone 5

• In Zone 5, average annual lows reach minus 20 degrees. The tree boxwood (B. sempervirens "Arborescens") is hardy in Zone 5 to Zone 8. This variety grows from 6 to 10 feet tall, with a conical 3- to 4-foot-wide spread. Tree boxwood has glossy, dark-green foliage and blooms with inconspicuous flowers in the spring. It prefers sun to partial shade and moist, well-drained soil. The "Vardar Valley" boxwood (B. sempervirens "Vardar Valley") is hardy in Zone 5b to Zone 8. This flat-topped shrub grows to 3 feet tall with a 6-foot spread. It has dense, leathery-green foliage and produces green flowers. Vardar Valley boxwood grows best in sites with sun to partial shade and well-drained, moist soil.
  
  

Zone 6

• To thrive in Zone 6, boxwood must tolerate average annual lows to minus 10 degrees. The littleleaf boxwood (B. sinica) is hardy in Zone 6 to Zone 9. It grows slowly to 3 or 4 feet tall with a similar spread. Littleleaf boxwood is named for its small, medium-green foliage that grows in a dense, compact mound. This drought-tolerant shrub attracts bees with its aromatic spring flowers and grows best in sun to partial shade and well-drained soil. The Japanese boxwood (Buxus microphylla var. japonica) is hardy in Zone 6 to Zone 9. It grows from 3 to 6 feet tall with a 4-foot spread, and has a rounded but loose shape. Japanese boxwood grows best in sun to partial shade and moist, well-drained soil. it tolerates drought and blooms with fragrant spring flowers.
  
  

Zone 7

• Zone 7's average annual lows reach zero degrees Fahrenheit. The "Harland" boxwood (B. harlandii) is hardy in Zone 7b to Zone 9. This shrub grows from 4 to 6 feet tall and has a similar spread. It grows in a dense mound or vase shape and has narrow, opposite, glossy but leathery foliage. This pest- and drought-tolerant boxwood prefers sun to partial shade and moist, well-drained soil. The "Morris Midget" Japanese boxwood (B. microphylla var. japonica "Morris Midget") is hardy in Zone 7 to Zone 8. This dwarf cultivar grows slowly in a low, mounded shape. It has yellow-green notched foliage. Morris Midget boxwood prefers partial shade and well-drained soil and tolerates heat well.