Q:Why are invasive, exotic plants considered to be nuisances?
A: They are not good because they escape from cultivation. While this may not be a bad trait for all species, those that are considered invasive have shown that they will aggressively invade surrounding properties, from natural lands to cultivated landscapes. Allowing these species to grow on one's property and to invade neighboring property is irresponsible, and their invasion may lower the value of the property being invaded.
Bamboo and camphor trees invading from neighboring properties have caused structural damage to homes, melaleuca trees and cogon grass are highly flammable and have caused catastrophic fires, and many aquatic exotic species interfere with stormwater drainage and cause fish kills. Villages in Africa have even engaged in biological terrorism--purposefully planting water hyacinths in the lakes that neighboring villages use for transportation and fishing. Water hyacinths quickly cover entire lakes and make it impossible to boat on them, and once established, water hyacinths are nearly impossible to eradicate.