Last month, people in all 50 states were mailed packets of unmarked seeds, CBS News reported. The seeds came from China and it appears they may be harmless, though little else is known about them. However, they may be “invasive plants.”
According to CBS News, officials issued warnings about packets of mystery seeds that appeared unsolicited in the mailboxes of Americans across the country last month.
“The USDA and agriculture officials across the U.S. have issued warnings about unsolicited shipments of foreign seeds and advised people not to plant them,” the article said. “Officials are concerned the mystery seeds, which appear to have originated in China, could be invasive plant species.”
Last week, a new clue in this strange story emerged. Fox Business reported that according to the USDA, some of the seeds have been identified. They include “mustard and cabbage seeds, plus flower breeds such as morning glory, hibiscus, and roses.”
Government officials are still stressing that recipients neither plant the seeds nor throw them away, but rather contact officials for further instructions. At the same time, the story does raise questions about which plant species are “invasive” and what that means.
Most people have had run-ins with poisonous plants like poison ivy, poison oak, or stinging nettles. However, invasive plants are a different category of nuisance.
“This term describes a plant that is not only a non-native plant in that it has been introduced from elsewhere, but also that it’s invaded into natural ecosystems and is taking over the habitat,” said Dr. Catherine Kleier, Professor of Biology and former Chair of the Department of Biology at Regis University in Denver, Colorado.
“One reason why invasive plants are able to take over so well is that typically, none of their enemies or competitors get introduced, too; so there are no other organisms to keep it in check, so it grows out of control.”
The Unusual Suspects
Most people don’t give much thought to where plant species come from, even when those species amount to fast-growing weeds. However, several invasive plants have spread far and wide.
“At least in the western United States, cheatgrass might be the most hated of all the introduced grasses,” Dr. Kleier said. “Cheatgrass came to the U.S. in grain feed accidentally, which was well distributed across the west by 1930. Cheatgrass gets its name from the way it would cheat ranchers out of good forage for their livestock.”
Dr. Kleier also pointed to the diffuse knapweed Centaurea diffusa as an invasive plant. A sort of cross between a thistle and a tumbleweed, knapweed plagues the Mediterranean area rather than North America. Nevertheless, it’s an uninvited guest wherever it shows.
In the south, the best-known invasive plant may be the kudzu vine.
“Amy Stewart, author of Wicked Plants: The Weed That Killed Abraham Lincoln’s Mother and Other Botanical Atrocities, writes that, to the Japanese, the word kudzu means rubbish, waste, or useless scraps,” Dr. Kleier said. “Kudzu was brought to the U.S. to control soil erosion around the time of the Great Dust Bowl in the 1930s. It’s rumored that this plant covers seven million acres and that it will take over the south.”
Regardless of which species is under the microscope, invasive plants can be a real bother. They tend to spread quickly and be of little use to any farmer or gardener who plants them. This is just another reason why authorities have asked recipients of mystery seeds in the mail not to plant them.
Dr. Catherine Kleier contributed to this article. Dr. Kleier is a Professor of Biology and former Chair of the Department of Biology at Regis University in Denver, Colorado. Professor Kleier holds a PhD in Organismic Biology, Ecology, and Evolution from the University of California, Los Angeles. She also holds a MS in General Science with an emphasis in botany and plant pathology from Oregon State University and a BA in Ecology, Population, and Organismic Biology from the University of Colorado Boulder.