Choose the Right Boxwood for Your Landscape

Evergreens, both trees and shrubs, enliven the winter landscape, providing form, texture and color during a time when our landscapes are sparse. Boxwoods are a common evergreen shrub used in many landscapes, prized for their dense compact shape and fine-textured, tidy, dark green foliage which is resistant to rabbit and deer feeding. They make an excellence hedge and are quite adaptable to varied pruning styles - they can be allowed to develop a natural open shape, pruned into formal borders or even used to create imaginative topiary forms.

 

However, boxwoods do have some drawbacks. First, their small dark green leaves are beautiful in summer, but can turn yellow or brownish in winter.  The foliage can also have an unpleasant smell, often compared to cat urine.

 

Finally, boxwoods are more challenging to grow well in Nebraska due to frequent problems with winter hardiness and winter desiccation. For these reasons, choosing the right cultivar is critical for their success in your landscape.

 

Boxwood Species
Nebraska encompasses USDA winter hardiness zones 4b, 5a, 5b and 6a, with the warm southeast corner of the state rated as zone 6a and the norther tier of counties our coldest area at zone 4b. Annual extreme minimum temperatures, averaged from 1991 to 2020, for each zone are listed below. Notice - there is a 20-degree difference in minimum temperature between zones 4b and 6a, so not all boxwood cultivars can be used throughout the state.    

 

Korean boxwood, Buxus sinica var. insularis (formerly B. microphylla var. koreana), is the most winter hardy species and reliably survives into to Zone 4. However, Korean boxwood’s foliage tends to turn yellowish-brown in winter reducing its attractiveness. Plants may reach a height of 5’ at 25 years if left unpruned, but are typically around 2-2.5’ in height and 4-5’ in width.

 

Common boxwood, B. sempervirens, is the next best choice for cold tolerance and can be winter hardy to Zone 5. Leaves are dark green above and light or yellowish green below in all seasons. However, new growth is very sensitive to cold temperatures, in either fall or spring. Plants should not be pruned too late in summer, enabling them to develop new growth which will be damaged by early fall frosts. Common box shrubs can reach 15-20’ in height with equal or greater spread, but plants can easily be maintained at lower heights through pruning.

 

Finally, littleleaf boxwood, B. microphylla, is only reliably winter hardy to Zone 6. Foliage is medium green in summer, changing to yellow/green/brown in winter. Plants typically reach 3-4’ in height with equal spread. Littleleaf boxwood is not well adapted for most of the state and should not be used outside zone 6.

To strive a good balance between cold hardiness and attractive winter foliage, look for cultivars created using Korean boxwood as one of the parents, to impart a higher level of cold hardiness, and common boxwood as the second parent for improved winter foliage color. With this in mind, cultivars to consider include the following.

 

Korean and common boxwood hybrids:

 

Be very careful when selecting other cultivars, especially littleleaf boxwood cultivars. It's unlikely they will survive or perform well given Nebraska’s cold, dry windy winter conditions.  

 

Plants perform best in a full sun to partially shaded location with well-drained soil. Boxwoods can grow in almost full shade, but shaded plants will be less vigorous, grow more slowly and develop a more open, sparse canopy of leaves. On the other hand, plants grown in full sun will be more susceptible to spider mite infestation, leaf bronzing and winter desiccation so finding a protected, partially shaded location is ideal.

 

To prevent foliage desiccation in summer and winter, provide even soil moisture and maintain a 2-3” layer of organic mulch around the base of each plant. Make sure plants are well-watered in fall and are fully hydrated going into winter to minimize desiccation problems. If possible, locate plants in an area with some winter wind protection; this will help minimize issues with bronzing and winter desiccation.

 

Locate plants where they can be enjoyed in summer and winter, but keep in mind they will have a “scent” and probably are not the best choice for a hedge around your backyard patio.