1. INVASIVE SPECIES:
In war against invasive plants, nurseries play unwitting role

Invasives may be tucked among these beautiful plants for sale at a nursery. Courtesy of the Montana Department of Agriculture.

The Norway maple is perhaps the country's most popular ornamental shade tree. A native of Europe, the maple is popular in the Northeast because it can tolerate cold weather and air pollution, and its shallow roots make it resistant to drought.

Millions of Norway maples have been sold at nurseries and had they stayed in the yards where they were planted, there would be no problem. But they spread quickly into nearby forests, where they tower over native sugar maples and birch trees, literally snuffing them out of existence.

The Norway maple stands as an example of how popular plants sold at nurseries are one of the most common -- and overlooked -- pathways for the spread of invasive plant species in the country. Go to story #1