He has served as a trustee since 2006 and he and his wife have opened their Cheshire garden for many years in support of the scheme (NGS).
He replaces Penny Snell who is standing down after six years in the post. She said: "Martin McMillan has already shown himself to be a wonderful supporter of the National Gardens Scheme and I know that he will bring many skills and lots of energy to leading the scheme through its 90th anniversary in 2017."
In 2012 Martin McMillan was appointed OBE for charitable services to the North West of England. He has served on the National Appeal Board for the NSPCC and the Cheshire Community Foundation. Currently he is the deputy chairman of Manchester’s world-renowned Hallé Orchestra, a post he has held for many years.
McMillan said he was honoured to be given the job, calling the NGS a "quite unique organisation".
"It is loved and admired by everyone who knows it and I want to harness that goodwill to build for the future. The NGS makes grants of approx. £2.5 million annually to nursing and caring charities having raised the money by organising volunteers to open their gardens for the scheme.
"I would like to raise the awareness of this fantastic organisation and as a result encourage more people to visit our gardens and to support us."
In 2015 some 3,800 gardens will open in support of the NGS, beginning in January and continuing through to the end of October. All details will be published at the end of January 2015 in the NGS’s guide, The Yellow Book and will be available on the website www.ngs.org.uk from the beginning of December.
Currently 80 per cent of the money raised at gardens is given away annually to the NGS beneficiary charities.