"The adjacent oak grove was planted in commemoration of the Diamond Jubilee of H.M. Queen Victoria 1897.
Thro' the coming years we trust
When we are [...] in the dust
Dunedin's children brave & strong
Will guard Victoria's Grove from wrong."
So says the inscription on this cairn at Jubilee Park in Dunedin's Green belt; sorry, I can't make out all the words. I've gone past there before on lunchtime walks, but never bothered to read the inscription, and I had to stand back to actually see the oak grove. You don't notice it when you stand under the trees!
So these oaks are now 133 years old - if my arithmetic holds up.
Oaks were a popular choice for commemorative plantings. This was possibly because of their longevity - they can live for hundreds of years in Europe. In New Zealand they grow twice as fast, and there has been debate whether they will therefore live half as long.