Blood Blossoms are blood-red flowers with anti-supernatural properties. They were used in the 1600s as a primitive ghost trap.
In "Infinite Realms", John Fenton Nightingale used these to create a barrier around Sam and then Danny, to try to "vanquish" Danny. The trio dispelled the barrier by having Tucker eat all the blossoms.
Blood Blossoms look like red rose blossoms, with a purple-trimmed black stem and leaves. When active, they release a red vapor.