They fell in love with the place after enjoying a guided tour of the property by Pompallier Mission and printery guide Tracy Rewiri a few years ago.
"It's simply our favourite place in Russell, and we wanted to be part of it," Bridget said.
"There are a lot of English and exotic plants I love – the Palestinian arum lilies, which are a chocolate brown colour, velvety… but also the Peruvian fushia (Fushia Corymbiflora), the blue sage and the Three Kings Lillies."
David's favourite – apart from fine-tuning Pompallier Mission's irrigation systems – was always the historic vegetable garden which, given its heritage significance, is subject to careful controls to preserve its heritage values.
"I'm a bit dangerous when I hear the word 'weeding'," he laughed.
Both have come to appreciate the importance of the garden over the years and what it represents.
Reflecting on the exotic nature of the garden, the discussion flows to people, and how Russell was a melting pot when the gardens were created at the end of the 19th century.
"This was the cradle of our nation, with European, Māori and people from all over the world living together here," Bridget said.
"The diversity of plants in the garden reflect this."
The style, indeed, is classified as "promiscuous" – a bit of a paradox, given that this was an ex-mission site.
Bridget and David have made a huge contribution to the gardens and have been a wonderful addition to the team, according to Pompallier Mission and Printery Property Lead Delphine Moise-Elise, who is quick to acknowledge the importance of volunteers to the work of Heritage New Zealand Pouhere Taonga.
"People who volunteer are precious and critical to our work, not only because they bring their expertise, passion, selfless dedication, experience and knowledge but because, through them, the spirit of a community exists and is alive on our heritage sites," Moise-Elise said.
"Volunteers manifest a sense of ownership and responsibility from the local community, which is essential to our vision to 'honour the past and inspire the future; Tairangahia a tua whakarere; Tātakihia ngā reanga o amuri ake nei'."
Volunteers also enthuse others with their rich and eventful life experiences and maturity of outlook, according to Moise-Elise.
"Their work ethic is an inspiration for the new generations, for all of us, and we are truly grateful," she said.
"It is also a way for keen gardeners, for example, to socialise, interact and enjoy our exceptional heritage gardens and grounds at Pompallier on a daily basis.
"Volunteering brings benefits all round."
Bridget and David Hallsworth are heading off on their next adventure, moving to their new-found paradise retreat near the Whangarei Heads, with their two donkeys and hens in tow.
Their four acres of native bush and gardens promise plenty of enjoyment ahead.
"We are going to miss Bridget and David, though lucky for us the Russell Gardening Club has offered to contribute, and we met our new wonderful garden volunteers last week," Moise-Elise said.
"Bridget and David are proud of their legacy and are glad to hear that someone will be following in their footsteps."