千百万年的磨合往往使一个地方生存下来的物种相互依存。因此外来杂草在原产地绝大多数并非有害杂草。而到了一个新的环境,一些发展势头强劲的植物失去了冤家对头,当地物种还没有对它形成遏制之势,它们便以排山倒海之势挤压过去,令对手只有招架之功,而无还手之力。豚草、水花生 Millions of years of running-in often make interdependent species living in one place. Therefore, the vast majority of foreign weeds in origin is not harmful to weeds. In a new environment, some plants with strong momentum of development have lost their antagonists and the local species have not curbed it. They have squeezed past the ups and downs in order to make their opponents only have the power to fight back and not fight back force. Ragweed, water peanut