The Canadian Food Inspection Agency is warning gardeners not to plant "unauthorized seeds" from packages they weren't expecting.
The agency says it's investigating reports of people receiving unsolicited shipments of seeds.
Authorities warn that "unauthorized seeds" could sprout into invasive plants or carry pests that can be harmful if introduced to Canada.
They say these species can invade agricultural and natural areas, causing "serious damage to our plant resources."
The agency is asking people who received unrequested seed shipments to contact their regional office "immediately," and hang on to the packaging and its contents until they hear from an inspector.
The United States Department of Agriculture says it's aware of "suspicious," unsolicited seed packages that appear to have been shipped across the country from China.