1 part Vervain herb
1 part Wormwood herb
1 part powdered Sandalwood or Rose Petals
1 part Dittany of Crete
1 part gum benzoin
Few drops of Olive Oil
Few drops of Red Wine
few drops of honey
Few drops of blood
Many, many plants have historically been associated with the dead and the spirit world; often these were grave goods, or plants traditionally grown in cemeteries.
The plant traditionally associated with raising the dead is the yew, but there are many other plants which are associated with the dead for the purpose of summoning the spirits, most often to entice the spirit into answering questions about the future. The magical incense burned by witches to attract spirits and help the materialize is known as a "suffumigation".
Various plants were used in suffumigations, including anise, dried carnation flowers, amaranth flowers, and gardenia petals, dittany of Crete, frankincense, heather, pipsissewa, sweetgrass, and wormwood. Dittany, in particular, was considered an excellent base; spirits would appear in the center of the smoke. Balm of gillead was also burned as a material basis for spirits. Asafoetida destroys the spirit manifestations when thrown into the fire (although I've also found information that it pulls in negative spirits).
Sandalwood is very commonly combined with other herbs for conjuring spirits. Wormwood, mixed with sandalwood, should be burned while in a graveyard. This will cause the spirits of the dead there to rise and speak. Crushed willow bark with sandalwood should be burned outdoors during the waning moon for conjuring. Sandalwood and frankincense is burned during seances. Lavender is also mixed with sandalwood for spirit summoning.
An incense for summoning recalcitrant spirits consists of three parts wormwood and one part Solomon's Seal. This is good for human dead who are not in very helpful moods. An incense for summoning spirits which were in a depressed state when they died consists of three parts wormwood and one part vervain. This is also good for people who are not aware they are dead. This will not only call them, but will also lighten their mood. The ancient Greeks believed that wormwood should be burned on a fire of privet in order to summon the dead, since a fire of privet was thought to open the doors of the Underworld.