Wormwood is a plant with powerful, albeit bitter, properties. In Potions, it is most famously used in the form of an infusion, which suggests its leaves and stems are steeped in hot water to extract their magical qualities. The specific physical appearance of the plant is not described in detail, but its primary characteristic is its bitterness, which has both mundane and symbolic significance.
Wormwood's primary magical property is its potency as a soporific agent when combined with other ingredients. It is an essential component of the Draught of Living Death, a very powerful sleeping potion that can cause the drinker to fall into a death-like slumber. The standard recipe for this draught begins with adding powdered root of asphodel to an infusion of wormwood. It is also an ingredient in the Elixir to Induce Euphoria, a sunshine-yellow potion that induces a sense of irrational happiness in the drinker. The sprig of wormwood must be added after the solution has been stirred and has finished simmering. As a standard potion ingredient, wormwood is presumably available for student use from the student store cupboard in the Potions classroom at Hogwarts.
Wormwood is one of the very first potion ingredients Harry Potter is introduced to, and it is used to establish the difficult relationship between him and Professor Snape. During Harry's first Potions lesson, Snape humiliates him by asking a series of difficult questions, the first of which is: “Potter! What would I get if I added powdered root of asphodel to an infusion of wormwood?” Hermione Granger knows the answer is the Draught of Living Death, but Snape ignores her. This moment marks the beginning of Snape's long-standing antagonism toward Harry. Years later, in their sixth year, Harry successfully brews a perfect Draught of Living Death by following the handwritten notes in his copy of Advanced Potion-Making, which belonged to the Half-Blood Prince. His success in this task, which involved using an infusion of wormwood, earns him a bottle of Felix Felicis from Professor Slughorn.
Wormwood is a real-world plant, Artemisia absinthium, historically known for its extreme bitterness and its use as a primary ingredient in the alcoholic spirit absinthe. The name also has biblical connotations, appearing in the Book of Revelation where a star named “Wormwood” falls to earth and makes the waters bitter, symbolizing calamity and sorrow. In the context of the series, Snape's first question to Harry is often interpreted through the Victorian language of flowers (floriography):
When combined, the question “What would I get if I added powdered root of asphodel to an infusion of wormwood?” can be symbolically read as an expression of Snape's deepest secret: “I bitterly regret Lily's death and her absence causes me great sorrow.”