With Mother’s Day around the corner, U.S. Customs and Border Protection is reminding travelers that not all flowers are welcome at the border.

Americans flock to florists and markets each spring to buy bouquets for Mother’s Day and other cherished spring holidays. But while flowers may look harmless, officials say they can conceal pests capable of ravaging U.S. agriculture.

“Flowers are a wonderful gift for Mother’s Day, but they could also be a hiding place for dangerous pests that could harm our country,” said Carlos C. Martel, Director of Field Operations for CBP’s Miami and Tampa offices. “I commend our CBP agriculture specialists for the incredible work they do every day. They are the first line of defense against destructive pests. Their vigilance and dedication inspecting cut flowers ensure these flowers are free from invasive pests, and our nation’s agriculture is protected.”

CBP agriculture specialists have inspected more than 1.2 million cut flower stems this spring ahead of the May 11 holiday, according to a May 6 press release. By comparison, the agency says it processed a record 1.3 billion flower stems during the Valentine’s Day season earlier this year.

Despite the scale of flower imports, only a fraction of shipments contain harmful pests. Still, even a single insect can be catastrophic. One such example is the Nysius, or seed bug, which CBP says can destroy entire crop fields. As of May 4, CBP agriculture specialists had intercepted 552 pests in 1,081 Mother’s Day-related shipments.

In a separate release issued May 2, CBP’s San Diego Field Office urged travelers not to bring restricted plants or soil across the U.S.-Mexico border this holiday season.

“This time of year sees a surge in flower imports, which can pose a risk to American agriculture by bringing in pests and diseases,” the statement read. “To protect U.S. crops and the environment, certain flowers, plants, and soil are not allowed to cross the border.”

Among the most frequently intercepted items is the Chrysanthemum, which is prohibited from entering U.S. passenger ports when brought from Mexico due to the risk of Chrysanthemum White Rust, a damaging fungal disease. Other risks include bouquet fillers like Murraya (orange jasmine), which can carry the Asian citrus psyllid, a pest capable of devastating citrus crops.

To detect threats, CBP agriculture specialists conduct hands-on inspections that include shaking flowers to dislodge hidden insects and using magnifying glasses to identify potential infestations. When pests are found, they are sent to the U.S. Department of Agriculture, where experts use digital imaging and other technology to analyze them.

CBP emphasized that while many flowers—including roses and carnations—are typically allowed entry after inspection, plants intended for cultivation must have the proper permits. Soil is banned outright.

“All travelers must declare any plants or flowers to CBP officers upon arrival,” the agency said. “Even though harmful pests are found in only a small percentage of inspected flowers, just one invasive species could lead to extensive crop damage.”

CBP advises travelers to check the Bringing Agricultural Products Into the United States page and the Know Before You Go guide before attempting to carry any agricultural products across the border.

CBP describes itself as “America’s frontline: the nation’s largest law enforcement organization and the world’s first unified border management agency.” With more than 65,000 personnel, the agency says it works to “protect America on the ground, in the air, and on the seas” and is committed to safeguarding travel and trade, ensuring economic prosperity, and securing the homeland through “innovation, intelligence, collaboration, and trust.”

Mother’s Day falls on Sunday, May 11.