A box tree which is believed to be more than 100 years old was stolen from outside a house in Gretton.
The tree, which has a 4ft circumference, was taken sometime between 11pm on Tuesday, December 22, and 10am the following day.
Tyre tracks were left in the garden when the tree was taken, so it is believed a 4X4 vehicle may have been used by the thieves.
Witnesses, or anyone who knows anything about this incident can call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org