The Cultivar Solution, Part 2 CIRCUMVENTING BOXWOOD THREATS WITH ALTERNATIVE SPECIES Tim Wood, Spring Meadow Nursery
In the January/February 2020 issue of The Buckeye, I published an article titled The Cultivar Solution, which outlined the benefits of plant breeding to tame invasive species. When it comes to finding answers to the issues we face as breeders and propagators of woody ornamentals, thinking alternatively is often, if not always, necessary. Sometimes we can develop new cultivars that address emerging concerns. But just as often, existing cultivars can serve the same purpose as a threatened species, and are naturally immune to the perils they are experiencing. One such imperiled shrub is boxwood. Because of its functionality, adaptability, and deer resistance, boxwood is one of the most utilized landscape plants in the world. Unfortunately, boxwood blight, a lethal disease caused by the fungus Calonectria pseudonaviculatum, threatens this iconic shrub. The disease, well established in Europe, has crossed the big pond and is now killing boxwood in North America. Boxwood blight is a fungus spread by the transport of infected plants, then 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, but it could be a very long time before it is eliminated. 12 The Buckeye
While blight is currently boxwood's biggest nemesis, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) has just sent notice of a new, more lethal threat to our beloved boxwood: the box tree moth (Cydalima perspectalis). Box tree moth caterpillars feed primarily on boxwood and quickly kill boxwood plants when left unchecked. Brought to the U.S. on nursery plants shipped from Ontario, Canada, the APHIS has confirmed that the invasive pest is now present in multiple states. Boxwood isn't having an easy time of it. Many will go to great lengths to contain this new pest and create blight-resistant cultivars, and that's important work for the survival of this popular plant. But a more immediate, and possibly one of the simplest solutions, is to use alternative shrubs with the same utility. Because these alternatives are not boxwood, they are immune to the issues that boxwood currently faces. Two species with the greatest potential to be suitable boxwood substitutes are Ilex crenata, Japanese holly, and Ilex glabra, inkberry holly. Both have small, broad, evergreen leaves and dense branching that responds well to being sheared into hedges, globes, and spires. Pictured right, clockwise from top left: Gem Box® Ilex glabra, Gem Box® Ilex glabra, Strongbox® Ilex glabra 'Ilexfarrowtracey' onla.org
