Wandering the grassland trail at Wildwood Metropark this past weekend, I discovered that the liveliest plant in that particular area was autumn olive (Eleagnus umbellata). This lovely thug was introduced to this continent from its native Asia in 1830 but really took off after the US soil Conservation Service (worried much more about the Dust Bowl than about escaping plants in those days) recommended it for erosion control in the 1940's. Today, it has invaded grasslands in many parts of the US, in part because birds love its fall fruits and deposit them in various places.
Unfortunately, the eleagnus wasn't the only problem. Tatarian honeysuckle has naturalized in most parts of the US, crowding out native species.
It's too bad that beauty isn't always well-behaved.