Bradford pears and 24 other ornamental trees were developed from Callery pears — a species brought to America a century ago to save ravaged pear orchards. Now, their invasive descendants have been reported in more than 30 states.
“Worse than murder hornets!” was the tongue-in-cheek title of a U.S. Department of Agriculture webinar in 2020 about Callery pears including the two dozen thornless ornamental varieties sold since the 1960s.
“They’re a real menace,” said Jerrod Carlisle, who discovered that four trees in his yard had spawned thousands on his 50 acres in southern Indiana.
Carlisle realized the spiky flowering pears were a problem in 2019. When he cut or mowed them, new sprouts popped up. Trees sprayed with herbicide regrew leaves. Cutting off bark in a circle around the trunk kills most trees. Not these.
Indiana is among 12 midwestern and western states that have reported invasions, though most are in the South and Northeast.
Without regular maintenance, fields near seed-producing trees can be covered with sprouts within a couple of years, said James “J.T.” Vogt, a scientist at the U.S. Forest Service’s Southern Research Station in Georgia.
“If you mow it, it sprouts and you get a thicket,” he said. “If you burn it, it sprouts, too.”
Seedlings only a few months old bear spurs that can punch through tractor tires, said David R. Coyle, an assistant professor in Clemson University’s Department of Forestry and Environmental Conservation.
The stench wafting from the tree’s billows of white blossoms has been compared to perfume gone wrong, rotting fish, chlorine, and a cheese sandwich left in a car for a week. The trunks branch off in deep Vs, so after 15 to 20 years they tend to break in storms. Something regularly seen in Oklahoma.
In 1971, the USDA even put out a brochure about their care, touting them as trees that bloom several times from spring through fall, thrive in many climates and soils, and don’t attract plant pests.
Their adaptability is one reason they’re so invasive. Now, the USDA describes Callery pears as near ubiquitous and has been studying the best way to kill them.
The Oklahoma Cooperative Extension service says while difficult to remove, there are a few things you can do:
- Unless completely uprooted, herbicides will be needed. Follow-up treatments likely will be required.
- Talk to city representatives about controlling callery pear on city property and programs to discourage invasive plants within the city.
- Discuss invasive plants with your homeowners association and suggest removing them from common areas.
- Mowing is not an effective control method due to resprouting
- Trees less than 6 inches in diameter at the base can be killed with a basal bark method with either a spray bottle or backpack sprayer.
The Oklahoma Wildlife Department says you can replace invasive ornamental trees with these options, native to Oklahoma: Redbud (Cercis canadensis), Flowering dogwood (Cornus florida), Black gum (Nyssa sylvatica), Serviceberry (Amelanchier arborea), American plum (Prunus americana).
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