( Weeds ( ( ( are simply ) ( ( those plants ) ( that ( grow ( where ( they ( ( are not ) wanted ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Weeds)) (VP (VBP are) (ADVP (RB simply)) (NP (NP (DT those) (NNS plants)) (SBAR (WHNP (WDT that)) (S (VP (VBP grow) (SBAR (WHADVP (WRB where)) (S (NP (PRP they)) (VP (VBP are) (RB not) (VP (VBN wanted)))))))))) (. .)))
Weeds are simply those plants that grow where they are not wanted.
(ROOT (S (NP (NNS Weeds)) (VP (VBP are) (NP (NP (NNS plants)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBP grow) (SBAR (WHADVP (WRB where)) (S (NP (NNS people)) (VP (VBP do) (RB n't) (VP (VB want) (NP (PRP them)) (PP (TO to))))))) (CC and) (VP (MD can) (VP (VB take) (PRT (RP up)) (NP (NP (NN space) (CC and) (NN use) (NNS resources)) (SBAR (WHNP (WDT which)) (S (VP (VBZ hinders) (NP (NP (NN growth)) (PP (IN of) (NP (ADJP (RBR more) (JJ desirable)) (NNS plants))))))))))))))) (. .)))