O SINGER of Persephone!
In the dim meadows desolate
Dost thou remember Sicily?
Still through the ivy flits the bee
Where Amaryllis lies in state
O Singer of Persephone!
Simætha calls on Hecate
And hears the wild dogs at the gate;
Amaryllis is a genus of flowering bulbs, named after the Greek Mythological shepherdess. Wilde here could be referring to both. 
    The Greek Figure : One day, whilst picking flowers, Amaryllis' eyes met the young shepherd Alteo, whom she fell in love with instantly. Alteo, not interested in the attention received from girls, declared that he will love whoever brings a new and beautiful type of flower for him. 
 Amaryllis consulted the Oracle at Delphi, who told her to pierce her heart with an arrow and declare her love for Alteo in front of his home everyday. After many days and nights of pain and rejection from Alteo, her heart was almost bleeding out. Finally, her blood sprouted a large red flower from the ground, which she brought to the shepherd boy. Seeing the dedication of Amaryllis, as well as the gorgeous flower, Alteo wept and Amaryllis was healed. 
 But Wilde made a dramatic alteration to this tale: Alteo’s love for Amaryllis does not arrive on time, and she passes away. 
    The Flower  (which is named after the Greek Figure): Connecting to the theme of  Persephone , the Amaryllis flower is known to blossom and thrive even through winter, when Persephone’s agricultural powers are dormant. In this situation, even this flower (which may be a symbol for optimism in this poem) is dead. This stanza implies the same question to Theocritus as  the previous : even when optimism is dead, will you still be optimistic and remember happiness? 
 

Theocritus