Nelson Historical Society Journal, Volume 2, Issue 1, 1966
This a puzzling street. It originally ran, I think, down Milton Street and the Grove part of the name was dropped. In Jury lists of 1846 Milton Grove is still mentioned in addresses but so is another street called Grove Street, which did not figure in Street Lists of 1842. Grove Street appears on the maps as early as 1842. In the Examiner of April 8th, 1843, lists of jurors include' "Phillip Valle, Gent, page 28Grove St., In the Wood, and John Jennings Imrie, Grove St., Gent." The Grove Gardens also appear in advertisements in early Examiners so it is not surprising that the Grove part of the name was given to another street, possibly to avoid confusion.
It is not clear when the change was made, but it was after 1846. Hobhouse's map of 1859 is no use here as he does not even show Milton Street or Milton Grove. Later in a map of 1923 Milton Grove was used again for a street on the south bank of the Maitai opposite Shakespeare Walk but this has also been dropped.