Hammerhead Worms

Watch for Hammerhead Worms in Your Garden

A long, slimy flatworm with a weird-looking head sounds like something from a science fiction movie, but it’s real and it has been documented in the Knoxville area.

Hammerhead flatworms are named for the distinctive half-moon shape of their head. They are not native to the United States but are believed to have arrived from Southeast Asia in the soil of nursery plants early in the 20th century. In recent months they have been seen around Norris, Tennessee.  

The invasive, snake-like creatures may be seen during wet summer weather as they seek hot, humid environments. Hammerhead flatworms can grow up to 15 inches long but are usually 8 to 12 inches in length.  

Like many non-native species, they cause a problem for native species. The worms are carnivorous and feed primarily on earthworms and other soil-dwelling invertebrates that are beneficial to the overall health of soils. By eating native earthworms, the hammerheads reduce the quality of the soil.  

“Our ecosystem in this region depends on earthworms, as strange as that may sound,” explains Jack Muncy, senior land conditions specialist. “If earthworms are removed from the environment, plants and crops, even trees, are not able to get the nutrients they normally would. This is a similar effect we see with invasive species in the water, like zebra mussels—they upset the normal ecological balance.” 

How to get rid of them 

Hammerhead flatworms secrete a toxic slime that makes them unattractive to predators. This slime can cause skin irritation in humans, and the worms can also carry parasites. 

They are most likely spread through landscaping soil and nursery plants, so keep an eye out for them when you are putting new plants and soil in your yard or garden.   

“If you see one, don’t touch it with your bare hands,” cautions Muncy. “And if you cut them, they can regenerate. The best way to get rid of one is to completely cover it with salt or rubbing alcohol, or use gloves to place it in a bag and freeze it.” 

For more information on the hammerhead and how to eradicate them from your garden, check out North Carolina State Extension.