In Harry Potter and the Philosopher’s Stone, the first thing Snape asks Harry in Potions class is,
“Potter! What would I get if I added powdered root of asphodel to an infusion of wormwood?”
According to the Victorian Language of Flowers ,
asphodel(百合之一种) is a type of lily(百合花) meaning
‘my regrets follow you to the grave’
and wormwood(苦艾) means
’absence’and symbolizes bitter sorrow.
The entire question has a hidden meaning of
“I bitterly regret Lily’s death”.
Professor Albus Dumbledore: Lily… after all this time?
Professor Severus Snape: Always.