Ask Mr. Smarty Plants

Please read our How-To Article When is a Guest a Pest? which covers the things we would say about invasives.

The problem then is to define a "useful purpose." While some of our invasives are native that have gotten ahead of other plants due to environmental conditions, most invasives are non-native or alien. Some were stowaways on ships, some were seeded by birds or strong winds, or have gradually spread from connecting parts of the continent. Most, however, have been deliberately brought here for specific purposes, "useful" purposes in the eye of the conveyor. For instance:

The Amazing Story of Kudzu

Previous Mr. Smarty Plants answer-King Ranch Bluestem

The United States Arboretum - Invasive Plants

Plant Conservation Alliance's Alien Plant Working Group LEAST WANTED - Bastard Cabbage

On the other hand, to be the Devil's Advocate, let's consider photosynthesis. From a previous Mr. Smarty Plants answer: "When sunlight strikes a leaf, a process called photosynthesis is put into play, the plant converts the energy from the sun, combines it with water and nutrients in the plant, and metabolizes it into food to support the plant, form new structures within the plant, and store food in the roots. Along the way, it releases oxygen, which is a good thing for the human race. The plant uses carbon dioxide, not good for breathing in the process, and releases much needed oxygen as a waste product!" How cool is that? From sunlight and photosynthesis the whole food chain of Nature is begun. This happens in native plants, alien plants and invasive plants. It's hard to call a plant useless. It may be irritating, poisonous, ugly, intrusive, but it is still feeding all the lifeforms and providing oxygen.