This is one of the ingredients that John used to summon the demon. There are roughly 1300 species of this plant worldwide spread around the dry tropical to warm-temperate regions. Generally the leaves of acacias are feather like, having leaflets or primary divisions arranged on each side of a common stalk. In some species, the leaflets are suppressed, and the leaf-stalks become vertically flattened. A few species don't have leaves, but instead modified leaf-like photosynthetic stems functioning as leaves. The small flowers on this plant have fine, very small petals, and are arranged in dense clusters. In most species they are yellow or cream-colored but can be white, purple or red. Accacia is used for medicinal, ornamental, culinary, or pharmacological uses.
After their accident, John gives Sam a list of things to get from Bobby, which included acacia and oil of Abramelin. When Sam questions John what they are for, he tells Sam the ingredients are for protection. However, later Sam confronts John telling him he knows the acacia and oil of Abramelin weren't for warding off a demon, but used to summon one.