By Natalie Carmolli, Proven Winners® ColorChoice® Shrubs
For decades, boxwood has been one of the most reliable structural shrubs in gardens and landscapes. Dense evergreen foliage, adaptability to pruning, and usefulness in everything from formal hedges to informal borders made it nearly indispensable. Then came a series of challenges that caused many to reconsider their reliance on this classic shrub.
Boxwood blight, an aggressive fungal disease, spread rapidly through landscapes and nurseries after its first U.S. confirmation in 2011. Boxwood leafminer weakened plants from the inside out. In many areas, it began to feel as though boxwood might no longer be worth the risk. Designers searched for substitutes, and homeowners hesitated before planting what had once been a sure thing.
Identifying Resistant Cultivars
That outlook began to shift about six years ago, driven by research identifying cultivars with better disease resistance. The turning point came in 2020, when scientists from the USDA Agricultural Research Service and Rutgers University published "Ranking Resistance of Buxus Cultivars to Boxwood Blight — An Integrated Analysis" in the Journal of Environmental Horticulture. For the analysis, researchers combined data from earlier studies with new findings to create the most comprehensive and statistically consistent ranking of boxwood cultivars for blight resistance at the time. The work drew on 289 samples from the National Boxwood Collection at the U.S. National Arboretum, one of the world’s most extensive collections, with more than 700 varieties.
The results weren’t dramatic, but they gave us some useful information. They found that while no variety showed complete immunity, some were significantly less susceptible. Among the least susceptible were B. microphylla 'Little Missy', B. microphylla var. japonica 'Winter Gem', B. microphylla 'Compacta', and B. microphylla var. japonica 'Green Beauty'. These are not obscure collector's plants, several are widely available at nurseries and garden centers.
New, Improved Cultivars
Since that landmark research, boxwoods have come a long way. The NewGen® line from Saunders Brothers combines resistance to blight with protection against leafminer, a destructive boxwood pest. NewGen Freedom® and NewGen Independence® were specifically selected for these traits and are now widely available through Proven Winners® ColorChoice® shrubs, giving gardeners hardier, low-maintenance plants they can count on.
NewGen Freedom offers a compact, rounded habit well suited to low hedges and foundation plantings; New Gen Independence has a looser, more upright presentation, and is a faster grower than the former. Notably, the parent plant of NewGen Freedom consistently ranked among the least susceptible cultivars in USDA trials.
Boxwood Care
Variety selection is one piece of the puzzle, but it's not the whole picture. Lowering the risk of boxwood blight depends on using more resistant cultivars and practicing good plant maintenance. Proper care, including adequate spacing for air circulation, avoiding overhead irrigation, removing fallen leaf debris promptly, and sanitizing pruning tools between plants, goes a long way toward reducing the conditions the blight pathogen needs to thrive. A well-sited, well-maintained plant of a moderately resistant variety will often fare better than a neglected specimen of a highly rated one. That said, starting off with a notably blight and pest resistant variety, like the NewGen line of boxwood, is a great place to start.
The story of boxwood blight isn’t finished, and as of yet, no cultivar is completely immune. But with these improved varieties and smarter planting and care, gardeners and designers now have real tools to work with. Boxwood’s long history as a garden favorite in North America is far from over.
All articles are copyrighted and remain the property of the author.
With modern rose breeding, it is now possible to grow garden roses that have large fragrant blooms and excellent disease resistance. Click here for an interesting, informative article about modern roses.
Click here to sign up for our monthly NEWSLETTER packed with great articles and helpful tips for your home, garden and pets!
