Plant-out-of-place photo galleries:

http://wric.ucdavis.edu/photo_gallery/photo_gallery.htm

http://ipm.ucanr.edu/PMG/weeds_intro.html

Horseweed - Conyza canadensis

Herbicide treatment table for citrus:

http://ipm.ucanr.edu/PMG/r107700411.html

And if you are wondering what herbicide damage might look like on various plant species (this is heavily weighted to annuals and landscape plants):

http://herbicidesymptoms.ipm.ucanr.edu/index.cfm

Blueberry herbicide damage