Yellow flowers at PG

Quick puzzle for you: name these plants and find the nasty weed among them! Send your answers to me on the back of a crisp $100 bill and I will gleefully buy even more plants in your name, whether you win or not!

(Answers are below - no cheating)

Answers: 

Top row, left to right: Aeonium sp, Calendula officinalis, Oxalis pes-caprae (Sourgrass)

Bottom row: Chasmanthe floribunda var. duckittii, Euphrnia charcias, Cytisus scoparius (Scotch Broom)

Which one is the invasive weed? Oxalis AND Scotch Broom! Unless you planted the latter on purpose...