Monday-ish word: adventive

[ersatz-read.livejournal.com]

adventive (ăd-vĕn′tĭv), adj.

Not native, and usually not yet well established; exotic (as in plants or animals).

Here is the wikipedia entry.
The alkali grass (Distichlis spicata) pictured below is an introduced adventive species here in Wisconsin, apparently only recorded in a handful of places in two counties.



Etymology:  Latin adventus, arrival.