What is one reason why certain weeds are classified as exotic?

Certain weeds are classified as exotic because they are introduced from locations outside of their native habitats. This introduction can occur through various means such as human activity, global trade, or accidental transport. Once these plants are established in a new area, they can often thrive and spread rapidly, leading to potential ecological imbalances. Exotic weeds may outcompete local plant species for resources such as light, water, and nutrients, which can disrupt local ecosystems and agricultural practices.

The other options indicate characteristics that do not define exotic weeds. For instance, weeds that originate locally are considered native, while commonly accepted plants might refer to cultivated species that are not problematic. Additionally, the ability of a plant to grow well in all environments does not inherently make it exotic, as this characteristic can pertain to native species as well.