NATIVE LAWNGRASS?  Is St. Augustinegrass a native Florida turfgrass? We would like to prevent erosion problems around the parking lot in a nature area, but are not supposed to use invasive exotics. Miami  

ANSWER: No one knows. Humanity's first record of St. Augustinegrass was in 1788 from South Carolina, and the earliest record from Florida was in 1845. Thus St. Augustinegrass might be native to the New World, and was here to greet the first Europeans. However, another explanation is more plausible. The six wild relatives of St. Augustinegrass occur naturally only in the Old World, in Africa (where St. Augustinegrass was recorded in 1810), and along shorelines from the Indian Ocean to the South Pacific.

During European expansion, a small plant such as St. Augustinegrass would have gone unnoticed for centuries, long enough to hop a ship, and became established before anyone noticed. To complicate things, St. Augustinegrass is a seashore pioneer, like the coconut, and it might have jumped ahead of human migrations. Thus people may have brought it from the Old World to the New, but it subsequently got to Florida on its own.

The second aspect of your question is on invasiveness. 'Floratam' St. Augustinegrass has aberrant chromosome pairing--it's like a mule--and rarely produces viable seed. The few seedlings which have been observed are feeble. Thus the threat from invasion by the 'Floratam' cultivar is almost exclusively due to vegetative spread of its aboveground runners, which can be easily detected and killed. With moderate diligence and a mechanical barrier, 'Floratam' St. Augustinegrass can be prevented from invading natural areas.