Callery Pear · Pyrus calleryana · 'Bradford'
They were planted everywhere. They bloomed beautifully in spring, provided dappled shade in summer, and turned crimson in fall. Then came the smell. And the splitting. And the invasive spread across every fence line and abandoned lot in the eastern United States.
"What the heck is that smell?!"
What You Need to Know
Before we go deeper, here's the short version for anyone who just Googled "why does that tree smell like fish."
Bradford pear flowers produce trimethylamine and dimethylamine — compounds also found in rotting fish and certain bodily fluids. The tree isn't broken. This is just what it does, every spring, for about two weeks. Your neighbors aren't imagining it.
Bradford pears grow fast and look great — for about 15 to 20 years. Then their tight, upward branch angles create included bark that can't form proper wood unions. In a good storm, half the tree comes down. Often, half the tree comes down in a mediocre storm.
Bradford pears were bred to be sterile. But when different Callery pear varieties cross-pollinate — which they do readily — the offspring are fertile and viciously competitive. Drive any rural highway in spring and count the white-blooming trees along fence rows. Those aren't planted. Those escaped.
From the Guide
Deep dives into the science, history, and policy behind America's most controversial ornamental tree.
History & Origins
In the 1960s, the U.S. National Arboretum released Pyrus calleryana 'Bradford' as a disease-resistant, fast-growing, seasonally beautiful alternative to the American elm, which was being decimated by Dutch elm disease. It was everything urban planners wanted. For about fifteen years, it was perfect. Then the problems began arriving, slowly at first, then all at once.
Read Article →The Science of the Smell
A chemistry explainer on trimethylamine, pollinator strategy, and why flowers that smell terrible can still be evolutionarily successful.
Read Article →Structural Failure
The anatomy of included bark, co-dominant stems, and why your 20-year-old Bradford pear is living on borrowed time.
Read Article →Invasive Species
Cross-pollination, fertile offspring, and the ecological damage unfolding in roadsides and woodlands from Ohio to Georgia.
Read Article →Better Alternatives
Serviceberry, redbud, fringe tree, and others — a region-by-region guide to replacing Bradford pears with trees that won't turn on you.
Read Article →The Bradford pear's story is one of good intentions, inadequate foresight, and an ornamental horticulture industry that moved faster than the science. The data tells the story clearly.
What began as a thoughtful response to the elm crisis became one of the most widespread urban forestry mistakes in American history — one now being unwound at considerable public expense in state after state.
Explore the ResearchPear Aware Project
The legislative tide is turning. Here's where Callery pear has been banned, restricted, or flagged for phase-out — and where momentum is building. Full policy resources live under the Pear Aware Project.
* Status current as of site publication. Verify with your state's department of agriculture for the latest.