By Proven Winners® ColorChoice®, adapted from The Planter Hunter, by Tim Wood
Photographs courtesy of Proven Winners® ColorChoice®
Boxwood, because of its functionality and deer resistance, is one of the most utilized landscape plants in the world. Unfortunately, boxwood blight, a lethal disease caused by the fungus Calonectria pseudonaviculatum, is threatening this iconic shrub. The disease, well established in Europe, has crossed the big pond and is now killing boxwood in North America.
In the fall of 2011, boxwood blight was detected in North Carolina and Connecticut. Since then, it has been found in Alabama, Delaware, Florida, Georgia, Kentucky, Kansas, Massachusetts, Maryland, Missouri, New Jersey, New York, Ohio, Pennsylvania, Oregon, Tennessee, Virginia, West Virginia and most recently, in Michigan. The fungus is spread by the transport of infected plants, and from infected plants to healthy plants via hedge shears, animals, and human touch. It is a slow but methodical spread that continues to widen. With that spread, plant breeders and researchers have been working to solve this problem.
One of the simplest solutions is to use alternative plants that have the same utility as boxwood but are unaffected by the disease. Fortunately, there are species that have great potential to be suitable boxwood substitutes. Species that have the same small, broad, evergreen leaves and dense branching that responds well to being sheared into hedges, globes, and spires.
Inkberry holly (Ilex glabra) is an Eastern North America native evergreen that is hardy in zones 5-9. Typically, it is a large plant maturing at 5-6 feet in height. It grows best in moist acid soils, but is adaptable to most average garden soils. Rutgers University lists it as moderately deer resistant, being seldom severely damaged by deer. Recently two new smaller selections have been introduced that look and behave like boxwood.
The first selection is called Gem Box® Ilex glabra. Gem Box® inkberry has extremely dense branching, small glossy leaves, but most importantly, unlike many generic versions of the species, it retains its lower foliage as it ages, making it an excellent replacement for boxwood. In the spring, with the initial flush of growth, the foliage exhibits an attractive cast of reddish-burgundy coloration. In the spring, if you look closely, you will find that it has small white flowers, and if you have a male pollinator nearby, you will also get small black fruit later in the summer. Neither the flowers nor the fruit are very noticeable. While the plants are naturally dense and rounded in habit, it responds wonderfully to pruning and can be sheared in globes or hedges with round or squared off edges.
Another native evergreen selection is Strongbox® Ilex glabra. It grows as a broadly rounded mound, and keeps its leaves all the way to the ground for a lush, dense look. It can be pruned or shaped as desired, or left to attain its neat natural shape. It's also much faster growing than boxwood, and offers good deer resistance, too. This brand new variety will be available in better garden centers in Spring 2019.
And now for something completely different: Juke Box® × Pyracomeles. This remarkable new broadleaf evergreen could easily be mistaken for boxwood. This new plant comes without the threat of boxwood blight because it is an intergeneric hybrid between Pyracantha and Osteomeles. It has no thorns, no flowers and like boxwood, can be sheared and shaped as desired. It is similar to 'Morris Midget' boxwood but with much faster growth. When left unpruned, it forms a thick, mounded evergreen mat, but with a little bit of shearing, it can be formed into a ball, box, or a low hedge. While hardiness on this new cultivar is still being tested, it is listed as hardy down to USDA zone 7, but may be hardy to zone 6 and perhaps even zone 5b.
While plant pests and diseases can be disruptive, they can also force us to think creatively and can bring new opportunities. There are so many beautiful and useful plant species in the world, so we have lots of choices. When it comes to replacing boxwood these three selections fit the niche.
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By Nancy Buley, J. Frank Schmidt & Son Co., Wholesale Tree Growers
Photographs courtesy of J. Frank Schmidt & Son Co.
The joy of flowering trees needn’t end with April showers and May flowers. By choosing trees that reserve their flowers for the long days of summer you can enjoy tree blooms in summer. To learn more click here for an interesting and informative article written by our friend Nancy.
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