A nondescript grass discovered in the Oregon countryside is hardly an alien invasion. Yet the plant – a genetically modified form of a grass commonly grown on golf courses – is worrying the US Department of Agriculture (USDA) enough that it is running its first full environmental impact assessment of a GM plant.

It is the first time a GM plant has escaped into the wild in the US, and it has managed it before securing USDA approval. The plant, creeping bentgrass (Agrostis stolonifera, carries a bacterial gene that makes it immune to the potent herbicide glyphosate, better known as Roundup. …