There are several plants, herbs and other natural materials that are extremely toxic to Vampires. Vampires can also find themselves in a uniquely deadly situation by ignoring a simple human custom.
Garlic: Upon consuming garlic a Vampire will immediately revert to its natural form complete with black eyeballs and visible fangs. While under the influence of garlic a Vampire will be unable to assume a convincing human like form and must appear as what they are.
Wooden Stakes: The surest way to kill a Vampire is to drive a wooden stake through it's heart. No Vampire in history has ever been able to ressurect itself after being staked through the heart. Upon being staked the Vampire will almost immediately burn up into ashes and there will not be enough of the body left to re-construct. Wooden stakes should preferably be carved from Ashwood as "Ygdrassill" The Norse "Tree of Life" is an Ashwood tree and failing that they should be carved from Aspen because Christ's crucifix was carved from Aspen wood.
Juniper: Juniper causes a slow acting, short lasting paralysis in Vampires. Whether fed Juniper directly or even if they are poisoned through Juniper infected human blood it is a powerful herb against Vampires. The effects of Juniper are like Rigor Mortis which leads some to believe that Juniper temporarily "clears" the Vampire gene from the body and allows the effects of death to catch up to the body. Generally the older a Vampire is the more effective Juniper will be.
Dogrose or Wolfsbane: When Dogrose or Wolfsbane is rubbed on the skin of a corpse a Vampire will mistake the scent for the scent of a Werewolf and will not attempt to turn the dead body into a Vampire.
"Let Me In" : A Vampire is unable to enter a private home or dwelling unless they are clearly offered an invitation by the owner of the home. If a Vampire enters a home uninvited he or she will burn to ash shortly after they intrude. Vampires can be very tricky in obtaining an invitation to the home and once they are invited in they are not bound by conventional human rules to respect the home and the home instantly becomes their territory. Bishop can be seen burning just seconds after invading the roommates' home and attempting to stake Aidan and narrowly escapes before being incinerated.