Starting in 2024, Callery pear (Pyrus calleryana), also known as “Bradford pear”, “ornamental pear” or just “flowering pear”, will no longer be available in Pennsylvania nurseries. This is because it’s being added to the Pennsylvania Department of Agriculture’s Controlled Plant & Noxious Weed List. Though long relied on as a horticultural staple, I welcome this decision. We’ll get into why, but first, some backstory is helpful.
Callery pears were introduced to the United States rootstock for fruiting pears as they were discovered to have great fire blight resistance and superb adaptability to a wide range of soils. In the 1950s, researchers observed a thornless Callery pear with an attractive habit and figured it would make an appealing ornamental. This introduction was named ‘Bradford’ which many people today are familiar with. By the late 1960s, ‘Bradford’ was being sold and planted everywhere.
Bradford pear trees had just about everything desired in a tree: attractive habit, fast growth, abundant flowers, vivid fall color, hardiness, disease resistance, and so on. Adding to their appeal, ‘Bradford’ was sometimes marketed as “fruitless” and thus “non-messy.” This claim was somewhat true because most pears, like apples, will not produce fruit unless they are pollinated with pollen from another variety (i.e., a plant with different genetics).
To ensure habit predictability, the Bradford pear was propagated by grafting stem cuttings on seed-grown rootstock. Since ‘Bradford’ cuttings were all from the same original tree, they were genetically identical (clones) and would not self-pollinate or pollinate each other. However, since they were grafted on seed-grow rootstock, this resulted in a situation where unpruned suckers would pollinate the Bradford pears growing on top of them. This, along with the introduction of additional ornamental cultivars such as ‘Autumn Blaze’, led to Callery pears bearing fruit.
After a couple decades, people began to realize ‘Bradford’ had poor structure when many would end up splitting during storms. With this knowledge, ‘Bradford’ fell out of favor and newer cultivars started to take its place. The most popular form today is ‘Cleveland Select.’ ‘Cleveland Select’ has a narrower habit than ‘Bradford’ with improved branching, making it less prone to storm damage. The dense, elliptical habit of this cultivar has also led it to becoming a popular street tree.
Though small and gritty to us, the fruit of ‘Bradford’ and other Callery pears are high in sugar which makes them appealing to birds (notably European starlings). Because the seeds have a high germination rate, and the trees themselves are highly adaptable, they began to rapidly spread into natural areas. Infestations are highest in sunny areas not inhabited by other trees such as meadows, prairies, and edge habitats. A high-profile local example of these invasions can be observed in spring by driving west on Hwy 376 towards the Pittsburgh International Airport. Clouds of white along the highway are all Callery pear offspring that have escaped from urban and suburban landscapes.
Today, it’s well known that Callery pear is invasive throughout much of the eastern United States. To reign in its spread, current and scheduled bans are also present in Delaware, Ohio, and South Carolina, with more likely to follow.
Invasive plants are nonnative plants, often originating from other continents at similar latitudes, that spread aggressively and displace native plants in the process. Invasive plants are usually vigorous in their original habitats and when introduced to a new environment, spread with little to keep them in check. With few insects and herbivores recognizing them as a food source, invasive plants contribute very little to their conquered ecosystems. This results in degraded or destroyed habitats.
Many nonnative landscaping plants, such Panicle hydrangea (Hydrangea paniculata), are well-behaved as they don’t spread into natural areas. Panicle hydrangeas are excellent garden specimens.
On the other side of this, some native plants can be aggressive, such as Pokeberry (Phytolacca americana). These plants, however, serve ecological roles and are still kept in check by various factors, so are never invasive. Since Callery pear is both nonnative and aggressive, these two factors combine to make it an invasive plant.
In the spirit of good Earth stewardship, the responsible thing moving forward is to not plant Callery pears. Just as we oppose littering, we should oppose botanical littering.
If you’re concerned about not being able to plant ornamental pears because you’re worried that your choices may be limited, don’t be. There are plenty of other trees that fill the same roles in the landscape. This becomes clearer every year with the introduction of newer cultivars. Truthfully, I consider Callery pear to be inferior and outdated anyway. You have better choices, and we’ll help you with them.
Check out Part 2 of this Blog Post here: Callery Pear Alternatives, Part 2 – Plumline Nursery
Callery Pear (Pyrus calleryana) (invasive.org)
The Rise and Fall of the Ornamental Callery Pear Tree | Arnold Arboretum (harvard.edu)
Scientists thought they had created the perfect tree. But it became a nightmare. – The Washington Post