( Petals ( ( are collectively ) ( called ( the corolla ) ) ) )
(ROOT (S (NP (NNS Petals)) (VP (VBP are) (ADVP (RB collectively)) (VP (VBN called) (NP (DT the) (NN corolla))))))
Petals are collectively called the corolla
(ROOT (S (NP (NP (DT All)) (PP (IN of) (NP (DT the) (NNS petals)))) (ADVP (RB together)) (VP (VBP are) (VP (VBN called) (NP (DT a) (NN corolla)))) (. .)))
All of the petals together are called a corolla.