this is a sentence from Another Evening at the Club

The spectres of the eucalyptus trees ranged along the garden fence rocked before her gaze, with white egrets slumbering on their high branches like huge white flowers among the thin leaves

The author most likely compares the eucalyptus trees to spectres to suggest

The woman is troubled by something
a sense of mystery about the woman (my guess is this)
the woman is in imminent danger
The fragile state of the woman's health