Here's a snippet ...

<i>The Greeks and the Romans continued this idea of yew as a symbol of death and regeneration. The tree was sacred to the goddess Hecate - Romans sacrificed black bulls wreathed in yew branches to Hecate at the midwinter feast of Saturnalia in the hope that she would provide an easier winter and spare the rest of their herds.

Christians built their churches on the Druids' ancient yew tree sacred groves, so continuing the association of yew trees with places of worship. For them the yew symbolised the resurrection of Christ and it was used in churches at Easter and on Palm Sunday, and burnt for ash on Ash Wednesday. They also put yew in the shrouds of the dead. Irish yews were much loved by Victorians and can be found forming long dark sombre avenues in graveyards of that period.

Legend has it that the roots of graveside yews reach into the mouths of the corpses. This is life in the mouth of death and is again the symbol of resurrection. Stories abound in Irish legends of yew trees growing out of graves to unite star-crossed lovers in death. Deirdre and Naoise's graves were staked by the High King Conchobar in order to separate them; yet the stakes grew into yew trees which wove their branches together over the graves and joined the lovers even in death. Tristan and Iseult were buried either side of the nave in the chapel of Tintagel Castle, Cornwall, and within a year yew trees had grown out of each grave. Despite being cut down many times they eventually grew together and intertwined, never again to be parted.</i>

from http://www.cvni.org/news_and_articles/yew/yew.html

Just a little factoid. The spreading yew tree isn't found much in Ireland. There are a few, the oldest being at Crom (Crom just happens to be the name of a Celtic god. Coincidence? Probably.) Irish yews are tall and the branches rise up similar to a poplar. There's one in this picture - http://www.megalithomania.com/show/image/4427