Sylvia Plath's Collected Poems contains work from all her major collections and is arranged chronologically in order of composition from 1956 to 1963. It also contains an appendix of fifty early poems (Plath's ‘Juvenilia’) and a list of more than 150 others written before 1956. This is the date which Ted Hughes, the editor of the collection, controversially defines as the starting point of her mature writing (CP 15). In collecting and defining this material as ‘Juvenilia’, Hughes has been accused of marginalising anything that Plath wrote in the years before meeting him, in other words, of dating her maturity as an artist to coincide with his involvement in her life and work. According to Jacqueline Rose, the effect of this is that ‘Hughes structures, punctuates, her writing definitively with himself.’ While some critics, such as Helen Vendler, agree with Hughes (these early poems, though ‘technically accomplished and psychologically truthful’ are not yet what she would categorise as mature), others dissent. Linda Wagner-Martin argues that ‘Plath was a serious writer right through her college years, beginning in 1950 … it seems clear that her poetry should be considered “mature” long before 1956.’

The relationship between the Juvenilia, early uncollected poems and Plath's later works – first the poems of The Colossus and Crossing the Water but primarily the poems of Ariel with which she made her name – has been of persistent concern to Plath critics.