The Tuscan, or "graveyard", cypress has long been associated with mourning, and is found in cemeteries across Europe. In classical mythology, the cypress is associated with Hades, god of the Underworld.
The yew's leaves are highly poisonous, which may have led to associations with death. Yew trees live a long time, with some trees dated at over a thousand years old. They are frequently found in English and French churchyards. In the British Isles, sacred associations may have predated the arrival of Christianity, and some churches are thought to have been built beside already venerated yews.
Junipers belong to the cypress family. Juniper trees are not commonly associated with churches or funerals, however some older specimens can look painfully contorted and half-dead, which may be what Stoker has in mind.