After a century of ever-changing displays of spectacular and rare plants, the Wintergarden glasshouses in the Auckland Domain are nearing the end of a 21st-century seismic and heritage overhaul.
The two glasshouses facing a courtyard with neoclassical statues and a sunken pool, with a fernery in a former scoria quarry to one side, have been a popular attraction for generations of Aucklanders and tourists.
But like so many historic buildings, the Victorian-style glasshouses have needed earthquake strengthening.
Auckland Council has used the opportunity to spruce up the Wintergarden complex, including installing external night-time lighting and switching from gas to a more climate-friendly biomass boiler.
To address another climate change risk, a new rainwater system, including wider gutters, is being installed to cope with heavy downpours and stop water seeping into the glasshouses.
The $7.5 million project follows significant renovations in 1993-1994, but this time the focus is on seismic strengthening, with new internal steel ties, stronger aluminum glazing bars on the roof, timber repairs, and laminated clear glass to meet the new building safety code.
The buildings originally had clear glass, but this was removed in the 1940s for opaque glass to stop plants from getting burnt by the sun, and later painted white for the same reason. With today’s technology of UV coating filters, clear glass makes a return and floods the glasshouses with natural light.
Council seismic technical programme manager Moustafa Swidan said the Wintergarden was initially assessed in early 2015 as being earthquake-prone at 30 per cent of the New Building Standard(NBS) rating.
Anything less than 34 per cent is considered earthquake-prone.
A detailed seismic assessment later in 2015 came up with a 21 per cent NBS rating and identified several problems, including the roof structure and brittle glass glazed roof, unstable masonry walls, and unreinforced masonry on the chimney in the tropical glasshouse, Swidan said.
He said the strengthening works would bring the Wintergarden to a 67 per cent NBS rating.
The Wintergarden was built following the Industrial, Agricultural and Mining Exhibition of 1913-1914 on the same site with significant financial backing from the exhibition chairman Sir George Elliott, who was also chairman of the Bank of New Zealand.
The temperate and tropical glasshouses were constructed of unreinforced piers supporting semi-circular steel truss frames between 1921 and 1929.
The temperate house opened in 1921 with the tropical house, courtyard and fernery added later in the 1920s. Auckland city mayor George Baildon officially opened the complex on May 2, 1928.
Nina Quintana, the council officer overseeing the 18-month project, said the biggest challenge has been combining the seismic work with the Wintergarden’s Category 1 heritage status, as one of the oldest botanic structures in New Zealand.
Thomas Nieuwenhuis, an architectural graduate with the specialist heritage firm Salmond Reed Architects, said it was important the seismic work did not negatively impact the overall architecture.
Any new work or alterations were kept to the minimum necessary to bring a building designed 100 years ago to modern building standards, he said.
For example, the new seismic strengthening steel members are painted in a slightly darker grey colour than the original steelwork to subtly distinguish the new work from the existing heritage fabric.
Planning for the project started 10 years ago and building work started just before the Covid-19 pandemic in 2020. The temperate glasshouse opened in May this year and the tropical glasshouse is due to open in March next year.
Even with Covid and inflation, the project is tracking to budget, Quintana said.
Karl Beaufort, the council manager for the Domain, said the temperate house is where the annuals and perennial flowers from around the world are displayed, including fantastic floral displays and a wonderful cacti display in winter.
The tropical house, heated at between 18C and 28C, contains rare orchids, a cacao tree, which seeds coca beans; a mango tree, a traveller’s palm from Madagascar and other rare and unusual plants that cannot grow in Auckland’s climate.
Two popular attractions are the infamous “corpse flower”, a giant flower that smells of rotting flesh on the rare occasion it blooms every five or 10 years for up to 48 hours, attracting hundreds of people who line up to get a whiff.
The other big attraction is the Victoria amazonica, a giant water lily that sits in the central water pond, with huge leaves that can hold a small child or dog, and the only example in New Zealand.
“Quite often it grows and flowers for a couple of years then dies. We have to make sure we get the pups that come off it or get it pollinated so we can catch the seed because if we lose it, it’s very hard to get it back in the country.
“The original one was gifted by Kew Gardens many years ago. About two years ago we gifted one to Wellington where they purpose-built a pond for the Victoria amazonica, but they have never been able to get one to grow in it,” Beaufort said.
He said a growing problem at the Wintergardens is plant theft, which has become so severe it has led to the installation of security cameras.
Thefts range from people taking cuttings with scissors hidden in handbags to a pond full of water lilies disappearing overnight and people walking out with cactus plants that have taken 50 years to cultivate.
Tropical hoyas, with their small clusters of flowers and easy to grow in Auckland, are a popular target. So, too, are rarer, hard-to-grow orchids.
Beaufort said the popularity of plants and value of plants has sky-rocketed, which makes it really important the council’s collection of plants goes on display for everyone to see.
“There are a lot of plants that people would not be able to grow in their garden, particularly in the tropical house where we keep controlled temperatures.
“The Wintergardens are a real gem of Auckland. We want to showcase it as much as possible,” said the council guardian.
The protest will pass over the harbour bridge this morning.