Well-travelled, Plumtree began his professional coaching career in Wales with Swansea, moving to South Africa and enjoying a term in charge of Ireland's forwards. He has more than done his time.
Holland, who like Plumtree has signed until 2021, also joined the Hurricanes in 2015 after moving from Canterbury. He will be expected to assume attack and backline duties.
The final mix of the coaching staff for 2019 is yet to be confirmed, leaving question marks over the future of technical coach Richard Watt and scrum specialist Dan Cron. With Boyd leaving, the Hurricanes may feel another backline assistant is needed.
"We're fortunate that someone of Plum's calibre has already been a key part of the Hurricanes environment," Hurricanes chief executive Avan Lee said. "Having both him and Jason at the helm will certainly ensure some important continuity and familiarity, but more importantly, we know they are a formidable coaching combination.
"We know that these appointments will be pretty popular with our fans.
"This does mean that with both Plum and Jason working alongside Chris this year, we are in the best position for a smooth transition to a new management team and new season in 2019. In the meantime, it is important to acknowledge that Chris has done a fantastic job in steering the ship and he continues to keep everyone focussed on our current season."
New Zealand Rugby general manager of rugby Neil Sorensen gave his seal of approval to Plumtree's appointment.
"New Zealand Rugby is lucky to have a home-grown coach with such vast experience in a variety of high performance rugby environments," Sorensen said.
"The Hurricanes performances over the past three years has reflected Plum's influence, especially his defensive expertise, and no doubt that will grow further as he takes the head coaching reins."