The trust also administers an education centre at the site, and thousands of people have visited on school trips and camps.
Originally, the buildings were home to many farm cadets who honed their farming skills on Tutira Station, and provided labour.
One of those cadets was David Allan, who succeeded John Nott as the trust chairman last year. Mr Nott is a former managing director of Williams and Kettle and retired after 38 years with the trust, the final 11 as chairman.
Over the past decade, the trust has been working to develop Guthrie-Smith into an asset for the region, with physical and financial support from Pan Pac Forest Products, the Hawke's Bay Regional Council, Department of Conservation, individuals and organisations.
A full-time curator, George Christison, was employed 11 years ago and is responsible for the extensive planting programme, and with the regular help of community services workers has overseen over $5 million worth of tracks, dams, fencing and other capital works.
Last year the trust moved closer to its goal of opening up Guthrie-Smith as an all-year-round visitor destination, with the creation of a new brand.
A free open day, with escorted walking tours, will be held at the arboretum from 11.30am to 4pm, on Sunday.
A bus will travel from Havelock North through to Napier and return, for a cost of $10 per person (children free).
Otherwise, visitors can get there by car. The trip takes 30 minutes from Napier.