Saunders Genetics is taking the initiative, pushing beyond growing protocols and monitoring, with diligent trialing and evaluation.

We’ve been working since 2008 on boxwood susceptibility to boxwood leafminer (Monarthropalpus flavus) and since 2015 on boxwood blight (Calonectria pseudonaviculata). These results have been compiled into an open-access, peer-reviewed research article appearing in the December 2022 issue of the Journal of Environmental Horticulture. Work continues as we search for the next introduction to our program. Read on for how this passion for finding the best in boxwood came about…

Boxwood Research Through the Years

By: Bennett Saunders

In the early 1970s Paul Saunders began hearing people say, “My English boxwood (Buxus sempervirens ‘Suffruticosa’) are dying.  My grandmother planted these boxwood, and for no apparent reason, they are turning a straw color, one limb at a time until the entire plant turns brown and dies.”

At that time, English boxwood was Saunders Brothers’ best-selling plant.  When customers wanted the best, they asked for English boxwood.  They wanted to frame their houses with the “aristocrat of boxwood,” and Saunders Brothers could deliver the goods.

Paul Saunders saw the English boxwood problem in his own gardens.  When an English boxwood was in any way stressed by extreme heat, cold, drought, loss of shade, or just simply old age, it started a slow, gruesome process of dying.  The die-back did not happen overnight, and Paul tried to hold onto the plants by adding fertilizer or lime, or watering them.  But nothing worked; no matter what he did, the “boxwood decline” continued, and eventually the entire plant died. 

Paul characterized Boxwood Decline as “a gradual decline in the health of English boxwood (Buxus sempervirens ‘Suffruticosa’), beginning with a limb or two turning brown, then continuing through other limbs on the plant over a period of months or even years, until the entire plant dies.  The complex problem is often associated with many possible causes including nematodes, drought, heat, cold damage, stress, old age, or some combination of these factors.  Once the plant begins to decline, it is nearly impossible to revive.  Replacing the dead or dying plant with another English boxwood is a vain effort.  The newly planted boxwood will begin to decline within a few years.”

At Paul Saunders’ request, even the President of Virginia Tech tried to help.  Dr. T. Marshall Hahn appointed a committee of eight scientists including four horticulturists and four plant pathologists to tour some of the sites where the problems were occurring, but they, too, were unable to come up with a unified answer.

The best solution seemed to be to change cultivars.  During the 1970s and 1980s, Paul Saunders scoured the mid-Atlantic region of the United States and identified a number of varieties which seemed to tolerate the complex problem.  In the quest to find plants that appeared resistant to Boxwood Decline, Paul found plants exhibiting other notable qualities such as varying degrees of resistance to Boxwood Leafminer, cold hardiness, a variety of leaf and plant sizes and shapes, cold-hardiness, and overall attractiveness in varying micro-climates.  What he saw gave him hope that he would find answers to the Boxwood Decline problem, but it also reminded him of how much he really did not know about the many other boxwood cultivars.

The National Boxwood Trials

Under a tent in Eastern Maryland in the mid 1990’s at a meeting of the American Boxwood Society, Paul Saunders made this appeal to the 40 or so attendees:  “We need your help in evaluating and choosing which boxwood to plant.”  Paul had collected many new cultivars, and promised that his nursery would give free samples to anyone interested in testing new cultivars.  He asked simply that the recipient agree to give him feedback, which Paul would then compile and share with the testers.

Paul also contacted some of the best horticulturists, educators, directors of arboreta and botanical gardens, and boxwood enthusiasts in the eastern United States.  Many of these individuals were familiar with Boxwood Decline and the futile effort to continue to plant English boxwood.  This group had a keen sense of other plant qualities which would be important in finding cultivars to replace English box.  Many of these testers already had some boxwood cultivars in their gardens, but Paul gave them additional cultivars to evaluate.  He became somewhat of a “Johnny Appleseed of Boxwood Cultivars”, driving the interstates with his wife Tatum to meet and exchange information with top boxwood enthusiasts.

In the late 1990s, Paul published his first edition of the “National Boxwood Trials”.  This report contained observations from over 40 test sites ranging from Connecticut to Alabama, and Chicago to Virginia Beach.  The report contained subjective research and observations made on a large number of new boxwood cultivars, opening the eyes of many to the huge range of boxwood germplasm available in the United States.

By 2000, Saunders Brothers, Inc. recognized that there was a huge market for larger size field-grown boxwood.  Bennett Saunders was assigned the task of growing these larger plants in the field.  In turn, much of the research work was also turned over to Bennett.

Boxwood Leafminer Becomes Big Problem

Buxus microphylla ‘Green Beauty’, Buxus x ‘Green Velvet’, Buxus sempervirens ‘Justin Brouwer’, and Buxus x ‘Green Mountain’ soon became huge sellers for Saunders Brothers, Inc. as well as other nurseries throughout the United States.  With time, however, these four boxwood cultivars were discovered to be highly susceptible Boxwood Leafminer damage.

Bennett noticed that the Boxwood Leafminer was cultivar-specific; that is, certain cultivars showed heavy infestations while other cultivars showed minimal, if any, damage by the burrowing larvae.  The Boxwood Leafminer damage was not only unsightly, but also caused heavily-infested plants to defoliate.

In 2007, Saunders Brothers, Inc. engaged Dr. Bob Dunn, a retired nematologist from the University of Florida, to collect data on natural resistance of cultivars to the Boxwood Leafminer.  Dunn planted replicated research trials in a boxwood growing area that was infested with Boxwood Leafminers.  He gathered data from almost 150 cultivars to determine natural varietal resistance to Boxwood Leafminer.  This data was critically important to Saunders Brothers, Inc. as there was no known reliable source of cultivar susceptibility information of the Leafminer.

In the meantime, Bennett traveled through the eastern United States, including Blandy Research Farm near Winchester, VA, the National Arboretum in Washington, D.C., and many nurseries and private collections, seeking other cultivars which showed natural resistance to the Leafminer. Many of these varieties were brought back to Saunders Brothers, Inc. for formal testing and to be added to the Saunders Brothers, Inc. collection.

Boxwood Blight

In 2011, Boxwood Blight was positively identified in the United States and immediately considered a game-changer.  Saunders Brothers knew from the get-go that Blight would be very problematic in the warm and humid climate of the Mid-Atlantic States.

In the spring of 2012, Saunders Brothers began to ship hundreds of cultivars that they had collected over the years to North Carolina State University.   Kelly Ivors, a research scientist in Mills River, North Carolina, began a 3-year study to determine the relative susceptibility of various boxwood cultivars to Boxwood Blight.  Ivor’s research found the cultivars that Saunders Brothers, Inc. delivered were highly variable in their respective susceptibility to the Blight.  Some cultivars showed extreme susceptibility and others showed good resistance to the disease, with all shades of susceptibility in-between.

Several years later Kelly Ivors moved to the West Coast, but Saunders Brothers, Inc. was determined to continue to research Boxwood Blight.  Bennett found a site about 150 miles away from the Saunders Brothers, Inc. nursery, in an obvious effort to minimize chances of bringing Box Blight to their home nursery in central Virginia.

It was here that Saunders Brothers began to do “real world testing” on a site that already had boxwood infected with Boxwood Blight.  Around these infected boxwood, they planted the most promising cultivars from Kelly Ivors’ research in replicated trials.  Bennett and others returned to this site 2-4 times during the course of the growing seasons to evaluate the degree of defoliation of the boxwood, depending upon weather conditions. 
It has always been important in the Saunders Brothers, Inc. research trials to select boxwood which consistently showed good results in different trials in different years.  As such, many of the cultivars were tested in as many as 5 or 6 different replicated trials. 

Over a period of eight years, at least 157 different cultivars were tested by Saunders Brothers, Inc. and Kelly Ivors.  Through this extensive research over many years, Bennett and the Saunders team saw how many different cultivars reacted to varying amounts of Boxwood Blight pressure in different seasons of the year as well as rainy or dry seasons. 

In the summer of 2018, Saunders Brothers, Inc. felt they had good answers to Boxwood Blight and Boxwood Leafminer problems after well over 10 years of intensive research.  Saunders Genetics LLC was created to: breed, source, test, evaluate, and market the best boxwood cultivars with consideration to all aspects of culture and garden performance. 

Research vs. Reality

What do we make of all this work?  What good is research?

Research provides unbiased data to boxwood enthusiasts and nurseries.  It is an integral factor about who NewGen™ is and what we stand for.  The Saunders Genetics initial selections of boxwood are based on three primary criteria: 

1. Resistance of Boxwood Blight based upon research;

2. Resistance to Boxwood Leafminer based upon research;

3. The “WOW Factor”, or impulse cosmetics, the most subjective of the three factors.

Any of the plants that Saunders Genetics chooses must have these three factors in order to be considered for the NewGen™ family of boxwood.

If a plant first displays these three criteria, Saunders Genetics also takes into account other factors such as cold hardiness, phytophthora susceptibility, grower friendliness, resiliency of the plant, growth habit, leaf size and structure, size of the mature plant, as well as several other considerations in order to make their final determination of which boxwood get the NewGen® label.

Their goal is to create an artist’s palette of boxwood cultivars with various shapes, sizes, and leaf traits to choose from, taking into account the inherent susceptibility of boxwood to various pests and diseases.