by Bobbie Schwartz A Pear with a Pair of Problems by George Brenn

A Pear With a Pair of Problems

By George Brenn, MIAH, Four Seasons Landscape Nursery, Inc.

Ubiquitous. Merriam-Webster defines this as “constantly encountered” and “widespread.”

To my mind, ubiquitous is a good term to describe a number of plant varieties seen in both residential and commercial landscapes. Those ubiquitous varieties would include Emerald Arborvitae, Goldsturm Rudbeckia and others. But the supreme entity on the ubiquitous list would have to be Callery Pear (Pyrus calleryana) and its many offspring, the most notorious of which is the Bradford Pear.

The story behind Bradford Pear is an interesting tale of good intentions gone bad. What seemed to be a “nearly perfect” tree when first introduced to the nursery industry has become a nemesis in this 21st century. And the ultimate insult to any selfrespecting landscape plant will surely become the fate of the Callery Pear family: invasive species.

The story begins on the West Coast of America. In the early 1900s, the fertile soils of Northern California and Southern Oregon had become famous for the production of European Pears (Pyrus communis). As time passed, the consumer demand for these delicious fruits grew, as did production. One single county in Southern Oregon reported their 1916 Pear production to be worth about $10 Million dollars (about $2.3 Billion in 2020 dollars).

However, there was a very dark cloud on this horizon: fire blight. In that same year, 1916, a California nurseryman wrote that Pear production in the San Joaquin Valley, once known for excellent European Pears, had been wiped out entirely by fire blight.

A plant scientist in Oregon had been working on the fire blight problem and learned that the Callery Pear, which came from China to the U.S. around 1908, was highly resistant to fire blight and might serve as a rootstock for the European varieties. However, to further his research, he needed more seed from China—seed containing the genetic code that made it resistant to the fire blight that was a death sentence to the European Pear varieties.

Now we get to the really good part of this story, the part where the government gets involved. Contact was made with a man named Fairchild at the USDA’s Office of Foreign Seed and Plant Introduction. Fairchild had been involved with bringing Japanese Cherries to Washington, D.C. He arranged for a “plant-hunter” from the Netherlands to travel back to China in search of Callery Pear seeds. The native Chinese Callery Pears were found in many locations ranging from dry mountain slopes to stream banks. Fruit production was quite sparse, and seed collection was laborious and time-consuming.

The collected seeds eventually ended up in two locations: a test orchard in Oregon, and at the U.S Plant Introduction Station in Glen Dale, MD. Here, seeds were planted, seedlings harvested and replanted, and the element of time, so essential in understanding plant performance and adaptability, was given its due.

We now move forward in time to the early 1950s, and a young horticulturist at Glen Dale named John Creech began to observe the Callery Pear plants growing there and to evaluate them for ornamental qualities instead of simply rootstocks. One tree, grown from seed acquired near Nanjing, was about 30 years old when Creech first evaluated it. He was impressed by its striking ornamental qualities, AND the fact that it was thornless. This tree had outstanding flowers, glossy foliage, was not troubled with insect or disease issues, and seemed to hold up well in storms. Creech was infatuated with this tree and determined that it held significant value as a landscape ornamental. He decided it should be named after a former Director of the Glen

Callery pear spreads near a Martin County Indiana roadway. Martin County was once home to one of the earliest Bradford Pear nurseries, located near the present day Crane Naval Base.

Prior to releasing this new tree to the nursery industry in 1960, Creech selected the new and treeless subdivision of University Park, near Washington, D.C. This area had poor quality soils, and Creech thought it would be an ideal place to test the adaptability of Bradford Pears. He planted about 180 young trees in 1954 and benefitted their form by pruning lower branches. The trees thrived, were vigorous and the decision was made to release Bradford Pear to nurserymen by inviting growers to take shoots to be grafted onto Callery Pear rootstocks. The unseen issue involved the DNA of the scions and that of the rootstocks.

Bradford Pears were soon in production in many nursery fields and became wildly (no pun intended) popular. It is true that the nursery industry promoted the ubiquity of flowering pears. Trees were in demand and growers delighted in the revenue source this new tree provided. However, the dark clouds of reality were looming. While those original University Park trees remained essentially fruitless, the rest of the population growing at the Glen Dale Station, the nearly 2,500 Callery Pear seedlings that were now good-sized trees, produced abundant fruit—small, but plentiful. Lesson learned: Bradford Pears planted in a mono-culture produce very minimal fruit, but when planted near other pears … fruit can be abundant!

Another relevant issue became apparent as Bradford Pear trees increased in age and size. While most of the University Park trees displayed reasonable sturdiness, many of the trees produced in nursery fields developed narrow crotch angles, and because of the inherent vigor of the species, branching was abundant, leading to a propensity for breakage along the branch bark ridge where tight branch angles often led to bark inclusions. The bigger the tree grew, the bigger the problem became.

Enterprising plantsmen recognized this “weak-wooded” issue and the original industry enthusiasm for ‘Bradford’ waned. They began evaluating and selecting trees that developed narrower crowns, more upright growth, etc. In the 1960s and later, newer cultivars entered the marketplace including ‘Aristocrat’, ‘Autumn Blaze’, ’Chanticleer’ and ‘Cleveland Select’ (probably the same tree), ‘Earlyred’, ‘Gladiator’, ‘Rancho’, ‘Redspire’, ‘Trinity’, and more. Even the U.S National Arboretum introduced new columnar forms named ‘Whitehouse’ and ‘Capital’, although both of these varieties have severe disease problems and are “out of favor.”

So, isn’t it a good idea to have diversity in plantings? For sure, diversity is beneficial in many circumstances. When you visit an orchard to pick apples, you find row after row of trees, but each row contains a different variety: ‘Red Delicious’ next to ‘McIntosh’ next to ‘Jonathan’ next to ‘Gala’ and so on. The reason they are planted in this manner is simple: crosspollination. Some plants are self-sterile, meaning they cannot pollinate themselves. Apples, pears, plums and sweet cherries are self-sterile and cannot produce fruit without the benefit of pollen from another tree of the same genus and species. The problem with fruit production in the Callery Pear plantings actually was diversity. With good intentions of solving the weak-wooded issue of Bradford Pear, the influx of new Pear varieties from the nursery industry was prompting the more serious problem of fruit production due to cross-pollination. The trees that started out being “essentially fruitless” were becoming anything but fruitless, much to the delight of birds. Plucking the small but plump fruits and depositing them along with a glob of purely organic fertilizer would lead to the demise of flowering Pear trees and the impending threat of inclusion among the list of invasive species. Yes, it is true that the birds and the bees have promoted the ubiquity of flowering pears.

We have all seen the result of this problem, although it may have gone unnoticed. Roadsides, vacant land, fence-rows, unmanaged properties and even well-kept landscapes can become new homes for volunteer Callery Pears. As an industry of the 21st century, we need to recognize this problem and take action. Should we still be selling Flowering Pears?

Just like the original evaluation of all those Callery Pear seedlings from China and the element of time that was required to assess the factors that bring value to any ornamental plant, the element of time has shown us the shortcomings of this tree. Without doubt, Bradford Pear is a tree with a pair (at least) of problems and we in the nursery industry today need to lessen the ubiquity of flowering pears.

Callery pear invading a forest in Daviess County Indiana

Author’s note: An in-depth article on the history of Bradford Pear can be found in a 2018 article appearing in the Washington Post Magazine entitled Scientists thought they had created the perfect tree. But it became a nightmare.

Editor's note: The Ohio Department of Agriculture has established new rules for invasive species, in which it determines Pyrus calleryana as invasive and will prohibit its sale and distribution in Ohio beginning January 7, 2023. For more details, visit agri.ohio.gov and search Invasive Plants. B

George may be contacted at george@fourseasonsvalpo.com. Photos provided by the Daviess-Martin CISMA, taken by Midwest Drone Services LLC