Every spring, all over South Carolina, we see yards, abandoned lots, natural areas, roadsides, and, in some cases, forests fill with white flowers. These first white flowers of the year are nearly all from the Callery pear tree (Pyrus calleryana). This tree is native to China, and while they may look the same, many of the trees planted in yards, around businesses, and in other managed landscapes across South Carolina are cultivars of P. calleryana. One of the most common cultivars is the Bradford pear (more information on Bradford pears can be found on this Clemson HGIC fact sheet HGIC 1006, Bradford Pear). Bradford pears, by themselves, cannot produce viable seed. But, if pollen from a different flowering pear cultivar (or a wild Callery pear) pollinates a Bradford pear flower, then viable seed can be produced. The fruit is often eaten by birds, and birds doing what birds do (hint: they fly and poop), spread the seeds across the land. When these new plants grow, they’re now Callery pears, the wild relative of Bradford and other cultivated varieties of Pyrus calleryana.
Figure 1. Callery pear blooming along the side of a road.
David Coyle, ©2024, Clemson University
Figure 2. Patches of Callery pear growing in a horse pasture. Horses can be injured by the thorns.
David Coyle, ©2024, Clemson University
Callery pears are an aggressive invasive species. The stems and branches possess thorns (sometimes up to 3” long!), they can spread by seed or through root sprouts, and they can quickly take over a roadside, old field, pasture, vacant lot, or forest understory. Once established, they’re difficult to remove because of the thorns, which can easily puncture skin, wound livestock, or pop tires on vehicles or implements. Prescribed fire is not a good way to clear the land of them, because research has shown that for every stem that a fire kills, four more will resprout in its place. Many herbicides, including glyphosate and triclopyr, are effective in killing Callery pear, and at this time, this is the best way to remove this plant.
Figure 3. Thorn on a Callery pear shoot. These are extremely sharp and can easily puncture skin, and many have reported the loss of tires from Callery pear thorn punctures.
David Coyle, ©2024, Clemson University
Figure 4. Callery pear leaves often turn a brilliant red color in the fall, making them easy to see on the landscape.
David Coyle, ©2024, Clemson University
Very few insects feed on Callery pears (or any of the cultivars), which means that songbirds (some of which require thousands of caterpillars just to raise a single clutch of eggs to adult birds) cannot find food on these trees. And since Callery pears typically crowd out native tree species, this can decrease the amount of food adult birds can find for their young.
Callery pears represent one of the most aggressive invasive plants we have in South Carolina, and a big part of why they’re a problem is because they can come, in part, from Bradford and other fertile Callery pear cultivars. Bradford pears are planted in many yards across the state and serve as pollen donors or recipients for Callery pears. Removing Bradford pears is one action landowners can take to help stop the spread of Callery pears.
The Bradford Pear Bounty Program, sponsored by Clemson Extension and the South Carolina Forestry Commission, is giving free native replacement trees to residents who remove their Bradford pear tree at four locations in South Carolina this spring: Hampton, Marion, Van Wyck, and Clinton. Information about the program is available at https://www.clemson.edu/extension/bradford-pear/.
