Are there plant species, in particular the weeds and those more aggressive and undesirable like kudzu, which are extraterrestrial?

As you have seen intuitively, it is very much the case that many plants of a pest variety and that are physically undesirable, or have dangerous characteristics where they may be toxic directly on contact, or have spiny protrusions that are painful, are intruders. So it is true that such species were introduced by extraterrestrials to darken the human environment and make it unpleasant. Kudzu is in this category as well because of its aggressiveness and the fact that it so chokes off other species and becomes a plague, of sorts, through its competition and ability to outgrow and smother more desirable plants, so it is an interloper par excellence.