But I would rather be horizontal.
I am not a tree with my root in the soil
Sucking up minerals and motherly love
So that each March I may gleam into leaf,
Nor am I the beauty of a garden bed
Attracting my share of Ahs and spectacularly painted,
Unknowing I must soon unpetal.
The speaker stands apart from the life cycle of a tree, which seems to have a pre-ordained purpose. She doesn’t blossom the way she feels she should or fulfill a / destiny like the tree does. 
 
 Curiously, the concept of “motherly love” is characterized as being strong in a tree’s existence, when in fact nearly all trees reproduce  asexually,  and don’t really have an equivalent for our concept of mother. Plath distorts our ingrained notions of family and kinship by transplanting them onto the natural world.
I Am Vertical