A Visit With DC’s Quarantined New Cherry Trees

Right now, the four saplings aren’t much to look at. Their foliage is sparse; their scrappy trunks are hardly thicker than a pinkie. Yet someday, if all goes well, thousands of people will wander beneath their blooming canopies each spring. The saplings are among the 250 cherry trees that Japan plans to give to the Unit­ed States, a gesture announced by the Japanese government after news broke that the National Park Service will need to remove about 150 of the trees at the Tidal Basin to repair its sinking seawall.

But because of strict laws governing the importation of certain plants (such as cherry trees, which are usually prohibited), the donated trees can’t just go straight into the ground: They must first spend two years at a facility in Laurel called the National Plant Germplasm Quarantine Center. It’s here that the first four saplings, presented by Japan’s prime minister during a ceremony in April, have begun the quarantine process.

Actually, it was the original gift of cherry trees in 1910 that led to this quarantine procedure in the first place. At the time, entomologists and botanists at the US Department of Agriculture were beginning to understand how much harm nonnative pests, fungi, and viruses could cause. So when they learned that 2,000 cherry trees were coming from Japan, they wanted to take a look.

What they found confirmed their fears: The trees were apparently teeming with pests and fungi. One entomologist described the shipment as among the worst infestations he had ever encountered. All 2,000 trees were set aflame on the grounds of the Washington Monument to curb the spread of the pests.

Japanese officials offered a new shipment, which arrived—pest-free—in 1912. But the significance of that debacle wasn’t lost on Congress, which soon passed the Plant Quarantine Act of 1912, granting the USDA authority to inspect all imported plants. That later led to the creation of the National Plant Germplasm Quarantine Center.

Recently, we got a first look at the young cherry trees in their temporary home at the center, where Paul Kanninen, the state plant health director for Maryland and DC, walked us through the process. When the saplings arrived, specialists performed initial inspections, looking for signs of pests or disease. The plants were then moved to one of the center’s quarantine screenhouses. There they’ll spend two years being watched by scientists, who regularly take samples and perform various molecular tests.

In general, about half of all pome and stone-fruit trees (which include cherry trees) in quarantine end up testing positive for something. The cherry saplings, which are being stored with other stone-fruit trees, look quite harmless, yet Kanninen says cherry trees are especially restricted imports because of their susceptibility to some diseases not currently found in the United States.

Fortunately, the four new trees have not thus far raised any red flags, and more should start arriving soon (though some of the 250 might be sourced from the US, allowing them to avoid quarantine). The goal is for all 250 trees to arrive in time for the 250th anniversary of America’s birth, which will be celebrated in 2026.

In the meantime, Kanninen and his USDA colleagues will have plenty of work to do. In 2022 alone, the United States imported more than 2 billion plants through its inspection stations. “We’ve learned the hard way that we need to look at things before we let them in,” says Kanninen. “Not that we don’t want to let things in. We do. We love plants.”

This article appears in the August 2024 issue of Washingtonian.

Jessica Ruf

Assistant Editor