In the gardening realm, awareness is a powerful tool. As any seasoned gardener will tell you, more experience and the more failures will make you a better steward and a more cognizant participant. We learn from mistakes — trowel and error, as some might say.
Boxwood blight has been affecting our local landscape for several years now, and is showing no signs of slowing down. Boxwood blight is a fungal disease caused by calonectria pseudonaviculata, showing up in North Carolina in 2011. Symptoms of boxwood blight include leaf spots with a dark margin, leaf drop and dark stem lesions.
I’ve written past columns about this plant disease — in terms of what it is, how it’s spread and its overall impact. But now is the time for examining solutions and talking about the silver lining.
Boxwood blight is an incurable disease. Once a boxwood becomes infected, there are basically two options. You can remove the infected plants and replace them with different plants, or you can opt to treat them with a combination of good horticultural practices and fungicides.
The overwhelming attitude over the last several years has been to take out infected boxwoods and replace them. This is a responsible means of sustainable gardening, granted that good sanitation practices are used in the removal and disposal process. This is how we evolve as gardeners and learn from nature.
This past spring, Reynolda decided to take action after discovering boxwood blight in the forecourt garden outside of the Reynolda House. The forecourt garden is also known as the sunken garden, and is between the house and the expansive lawn of the Reynolda Estate.
Until this past April, this garden was planted with a hedge of “Justin Brouwers” American boxwood. This dwarf cultivar has distinctively dense foliage, which is one of the many reasons it is an adored variety of boxwood. It is also highly susceptible to boxwood blight.
Reynolda Gardens Director Jon Roethling led the removal and replacement efforts, securing a donation of 300 inkberry holly plants from Spring Meadows Nursery. Spring Meadows is one of the largest woody-plant growers in the United States.
The replacement plant that Roethling chose was Ilex glabra “Gem Box,” a dwarf, native cultivar of inkberry holly. Similar in size, growth habit, and look, ‘Gem Box’ seemed to be a good fit for the forecourt garden.
“All the ‘Justin Brouwers’ are gone, which pained me because it’s a nice boxwood,” Roethling said. “But it was the perfect opportunity of operating in the spirit of Katharine. Let’s be ahead of this and be a shining example of what options are out there.”
“In probably two years, you won’t notice any difference. Only plant geeks will know that’s not a boxwood.”
Boxwood blight hasn’t shown up yet within the formal gardens of Reynolda Gardens. Roethling is hopeful that it won’t, but is realistic about the probability. He and the gardens staff are actively pruning existing boxwoods within the gardens to prevent blight.
Pruning and thinning is one of the proactive measures that people can take to prevent boxwood blight. The fungal disease is exacerbated by dense foliage, which can be helped with pruning.
“I’m kind of resigned that at some point it’s probably going to show up here,” Roethling said. “If we can mitigate it, that’s great. But if we can’t, we’ll be like gardeners — we’ll adapt.”
There are many options for boxwood replacements. The most popular seems to be inkberry holly (ilex glabra). Inkberry is a native shrub, which grows 6 to 8 feet high and wide. There is a wide range of native cultivars, including Nigra, Shamrock and Compacta. Newer dwarf cultivars include Gem Box and Strong Box, which only grow 2 to 3 feet tall and wide.
Other replacement plants include dwarf osmanthus, pyracomeles and Japanese hollies such as Hoogendorn, compacta and helleri.
The second option for dealing with boxwood blight is treatment. Nature’s Select Premium Turf Services is a local company that offers to treat infected boxwoods. The company is dedicated to organic and biological solutions for healthy landscapes. This philosophy is the root of their boxwood blight treatment program, as they are leading the way in local and regional boxwood care.
Treatment has only now started to prove effective, and it seems to be gaining ground in the landscape community.
“The best approach is organic and biological (treatment),” said Jeremiah Sullivan, a tree and shrub technician with Nature’s Select. “Even though you have all this blight, for 2018 boxwood sales exceeded holly sales. People in the industry want to fight this. But I don’t know that everybody knows how to fight it. It starts with horticultural practices.”
Boxwood blight commonly enters the plant through infected spores splashing upward from the ground and from spores being transferred by people or animals. It can be made worse, of course, by densely packed foliage that is devoid of air circulation, which breeds the fungal infection.
Sullivan’s treatment plan is a combination of pruning to increase air circulation, mulching, soil amending and a fungicide rotation usually applied once a month. These are all part of the good horticultural practices which Nature’s Select promotes.
“When you prune boxwoods to give them air and have that movement through it, you’re organically interrupting the biorhythm of the pathogen,” Sullivan said. “Good horticultural practices are about promoting oxygen. Oxygen is as important to shrubs as it is to us. And when you take that away and create an oxygen depleted environment with stale air and stale moisture, that is a scientific certainty that you’re going to create disease, fungus and dieback.”
Sullivan emphasized sanitation and cognition about handling and traveling between boxwood properties. Infected spores can travel on our shoes, clothing, tools and vehicles. Infected foliage can be thrown on the curb for city pickup, infecting compost piles for future use. Even if we’re removing infected boxwoods, we still have to be careful about spreading the disease to other properties in inadvertent manners.
“My best advice to the average person is sanitation practices,” Sullivan said. “I use Lysol concentrate in a spray bottle. Every boxwood property that I’m in and out of, I disinfect my hoses, my shoes, everything. Landscapers need to start doing the same thing; homeowners need to think about doing the same thing.”
Proper disposal includes carefully double-bagging infected foliage into black trash bags, and disposing at an infectious shrub dump site (which most city or county facilities have). If the property is in an area that allows, burning the infected plant material is ideal. Disinfect anything that came directly into contact with the foliage, including tools, clothing and tarps.
If you think you may have boxwoods infected with blight, it’s important to weigh the decision of removal vs. treatment. Roethling and Sullivan agree that treatment should be pursued if the shrubs are an integral backbone of your landscape or if you’re sentimental about their presence in your garden. If you see them as just a green shrub, then choose removal and replacement.
Boxwood blight is nothing to take lightly. But the more awareness that’s out there will allow us to become better stewards of the natural world.