( ( As ( an experiment ) ) ( , ( ( ( ( ( one year ) ( we ( ( planted seeds ) ( in ( late October ) ) ) ) ) and ) ( they ( started ( ( sprouting ( the ( next April ) ) ) ( when ( temperatures ( began ( to rise ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (PP (IN As) (NP (DT an) (NN experiment))) (, ,) (S (NP (CD one) (NN year)) (NP (PRP we)) (VP (VBD planted) (NP (NNS seeds)) (PP (IN in) (NP (RB late) (NNP October))))) (CC and) (S (NP (PRP they)) (VP (VBD started) (S (VP (VBG sprouting) (NP (DT the) (JJ next) (NNP April)) (SBAR (WHADVP (WRB when)) (S (NP (NNS temperatures)) (VP (VBD began) (S (VP (TO to) (VP (VB rise))))))))))) (. .)))
As an experiment, one year we planted seeds in late October and they started sprouting the next April when temperatures began to rise.
(ROOT (S (NP (NNP New) (NNS plants)) (VP (VBP start) (S (VP (VBG sprouting) (PP (ADVP (NP (CD two) (NNS months)) (RBR later)) (IN after) (NP (DT a) (NN forest) (NN fire)))))) (. .)))