Torpedo Grass - an invasive exotic grass


On our Second Saturday volunteer day this weekend I discovered Torpedo grass (Panicum repens) growing with such abandon in the entrance garden (off 34th Street) that the mondo grasses were hidden. 



Torpedo grass is a Category 1 invasive exotic plant on the 2017 Florida Exotic Pest Plant List (FLEPP). That means we can add this plant to our removal list (Carrotwood trees, Brazilan Pepper trees, Umbrella trees).

So what are invasive exotic plants?


They are plants that alter the native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives. This definition does not rely on the economic severity or geographic range of the problem, but on the documented ecological damage caused.


And they are very hard to rid. Some people say impossible.


I spent 3 hours today digging up its rhizomes. 




And there is more to do. U-FL recommends persistent monitoring to find and dig up the hard, sharp-pointed rhizomes that run horizontally underground, like a torpedo going through water. The rhizomes can travel a foot or more deep (true) and the hard points can punch through landscape fabric and weed barriers. Some people report the grass coming up through roads.

While digging, I wondered how this invasive got so thickly woven into the roots of the mondo grass.


Native to Africa and Asia, torpedo grass was introduced to the United States before 1876, primarily through seed used for forage crops. But it really became established in the early 1900s when the U.S. Department of Agriculture imported and distributed seed for planting in pasturelands to provide forage for cattle. Ironically, it proved inferior for use as a forage crop.


So that got it to Florida.


But how is it here in Wildewood? I dug more than a foot to release a rhizome piercing a hunk of old, hard, historic mulch. Maybe cheap mulch with torpedo grass seeds? 




Or, the mondo grass? Did the plant soil have rhizome bits in it? 

I don't know the origin. But I do know that it will take consistent work to clear the entrance garden of this nuisance. Even a fragment of rhizome will allow torpedo grass to re-establish.