What is the oldest tree in Birr?
Birr's oldest mapped tree is the Carroll Oak, a Pedunculate Oak (Quercus robur) in the parkland of Birr Castle Demesne. The estate says it was planted before the Parsons family arrived in 1620; the Irish Times put its planting around 1550.
The oak carries the name of the O'Carroll clan, who held Birr until the 1620s, though the estate does not say who planted it. In 2005 the Irish Times reckoned it had been planted about 455 years earlier and was set to last roughly as long again. The national heritage tree register gave it 300 to 500 years in 2009 and recorded it as a maiden oak, a single trunk never cut back. No girth or height has been published. The demesne's box hedges are at least two centuries old, with sources ranging from the 1780s to more than 300 years. The estate says the oak was certainly planted before the Parsons family arrived in 1620, and it is the only tree it places before them. In 2005 a trimmed circle was kept clear around its base. The box hedges stand on the lower terrace of the Formal Gardens, and the castle calls them the tallest in the world, though published heights run from nine to twelve metres. A dawn redwood from seed that reached Birr in the 1940s completes the three trees mapped here. The demesne is ticketed and open all year.
One of Birr's trees also appears in Autumn Worth the Trip.