The landscape maintenance contractor to the Queen looks after gardens for royal households such as Marlborough House and Windsor. It was first granted a five-year warrant in 2008 and was recently reappointed until 2017.
Director of business development Yvette Etcell said: "The warrant underlines our commitment to delivering an exceptional service for exceptional clients through our exceptional people. It has been hugely beneficial to our company profile."
Chairman Martyn Mogford was dubbed grantee of the warrant because it had to be awarded to an individual.