( ( A weed ) ( ( is ( ( a plant ) ( growing ( where ( it ( ( 's not ) wanted ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN weed)) (VP (VBZ is) (NP (NP (DT a) (NN plant)) (VP (VBG growing) (SBAR (WHADVP (WRB where)) (S (NP (PRP it)) (VP (VBZ 's) (RB not) (VP (VBD wanted)))))))) (. .)))
A weed is a plant growing where it's not  wanted.
(ROOT (S (NP (NP (NNS Plants)) (SBAR (WHNP (WDT that)) (S (VP (VBP grow) (SBAR (WHADVP (WRB where)) (S (NP (PRP you)) (VP (VBP do) (RB n't) (VP (VB want) (NP (PRP them)))))))))) (VP (VBP are) (VP (VBN called) (NP (NNS weeds)))) (. .)))