( ( ( Higher latitudes ) ( with ( longer ( summer ( day lengths ) ) ) ) ) ( ( are ( beneficial ( for ( increasing ( ( essential ( oil yield ) ) ( of mint ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJR Higher) (NNS latitudes)) (PP (IN with) (NP (JJR longer) (NN summer) (NN day) (NNS lengths)))) (VP (VBP are) (ADJP (JJ beneficial) (PP (IN for) (S (VP (VBG increasing) (NP (NP (JJ essential) (NN oil) (NN yield)) (PP (IN of) (NP (NN mint))))))))) (. .)))
Higher latitudes with longer summer day lengths are beneficial for  increasing essential oil yield of mint.
(ROOT (S (NP (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN increase)) (PP (IN in) (NP (NN length)))) (VP (VBZ happens) (PP (TO to) (NP (NN metal) (NN railroad) (NNS tracks))) (PP (IN during) (NP (NP (DT the) (NN heat)) (PP (IN of) (NP (DT a) (NN summer) (NN day)))))) (. .)))