A Wealth of Trees /
The planted beauty of the Harry Hart Arboretum at Lake Coleridge
Hydroelectric power stations built in the Canterbury High Country and North and Central Otago during the last hundred years have often been a catalyst for new tree planting in harsh environments – the Harry Hart Arboretum at Lake Coleridge and the Power Station itself are fine examples which have matured in tandem, and are within easy reach of central Canterbury and Christchurch.
Development of New Zealand’s power network has been essential, but not always kind to the landscape. Although power stations and artificial lakes have inevitably changed the wild open tussock country of the inland South Island, trees established with sensitivity to the surroundings have mostly been a positive element: at first for sheltering new homes of construction workers, and treasured in the longer term for their beauty, environmental and botanical value, and timber.
The area around Lake Coleridge and the Rakaia Gorge was ground into its present shape by a massive glacier over 20,000 years ago – literally a blockbuster 90 km-long river of ice reaching 165 m up the valley sides in places. It scoured out the lakebed from harder rocks, and like other glaciers along the east side of the main divide bulldozed mountains of shingle back and forth as wedges of ice advanced, retreated and finally melted into ‘gigantic torrential rivers’ as imagined by scientist and explorer Julius von Haast in 1879. The local landscape is an outdoor textbook of post-glacier features including accumulations of loose shingle, making construction very tricky.
Māori named the lake Whakamātau (meaning to experiment, try, or teach), hunting eels, moa and smaller birds for food as they trekked via the headwaters of the river to collect West Coast greenstone (pounamu). It is considered one of the great inland lakes dug out by legendary chief Rakaihautu as he explored the South Island. Europeans first surveyed the area as a possible route to the West Coast goldfields. Half the size (47 sq. km) of Lake Tekapo but nearly twice the depth (200 m) in parts, the lake was named in 1849 by the Canterbury Association’s chief surveyor
Joseph Thomas, for fellow association members Edward and William Coleridge. First cousins, they were also nephews of English poet and philosopher Samuel Taylor Coleridge who memorably wrote ‘In Xanadu did Kubla Khan A stately pleasure-dome decree…’
By 1900 Christchurch was using more electricity, and earlier options for new power generation included dams on the Waimakariri, and other rivers. However, in a geological quirk Lake Coleridge sits 165 m above the Rakaia riverbed, and a hydroelectric station there could be gravity-fed using in
effect existing natural storage. The New Zealand Government built its first hydroelectric plant in 1901 near Rotorua, but in comparison this proposed station was a monster, and at the bleeding edge of technology at the time. Its ultimate success contributed to the long-term government commitment to hydroelectric power generation.
Construction began in 1911, initially using hand tools and steam shovels. Loose shingle was challenging to build on, and new engineering techniques were developed to complete the powerhouse, considered a remarkable achievement at the time. Approximately 400 men lived in tents and timber sheds at first, in a bleak, exposed and completely treeless landscape – perishingly cold in winter and equally uncomfortable in summer as howling northwesterlies whipped dust and shingle from the riverbed. Permanent houses were gradually built and wives joined their husbands in the new village. The
The big concrete powerhouse has a simplified classicism in its overall proportions, and in certain details – an intriguing design.
official opening by the Prime Minister in November 1914 was celebrated by hundreds of Cantabrians from Christchurch and surrounding areas who had travelled for hours to mark a fundamental change to their quality of life. Two transmission lines to Christchurch were soon finished, delivering power from March 1915. The station eventually supplied power as far as Oamaru, Rangiora and the West Coast, before larger stations were built; and tributary rivers of the Rakaia had part of their flows diverted into Lake Coleridge to increase catchment: the Harper in 1921, Acheron in 1930 and Wilberforce in 1977.
Upgrading of machinery and technology, and more efficient power generation requiring less water has been an ongoing process for the station: for example in 2008 fluid dynamic modelling by computer was used to increase turbine efficiency by 12 per cent. Some of the turbines are
nearly a century old and still fully operational after careful refurbishment. The big concrete powerhouse has a simplified classicism in its overall proportions, and in certain details – an intriguing design, just prior to the Great War and only a few decades before international modernism in architecture. Features include a keystone and corbels cast around the grand entrance archway, tall multi-paned windows with smaller versions directly above like a British late-Georgian townhouse (nine of these upper windows have been blocked off ), recessed and projecting rectangular columns or pilasters marching along the façades, and an elegant cornice wrapped around the top of the whole structure.
Surrounded by tall peaks and quite close to the Main Divide, the local climate of Lake Coleridge and the arboretum is significantly different than out on the open plains.
Larch tree with colourful autumn foliage above the powerhouse, with Black Hill Range beyond.
Power Station staff and their families settled in the village as most of the construction workforce moved on to other projects. Wide shelterbelts of mainly radiata pines were now growing successfully around the earlier accommodation, a process started by the station’s resident construction engineer Frederick Kissel and first superintendent Archie Blackwood, but contemporary photographs show how much of the area was still open and unprotected. In 1923 the station’s second superintendent Harry Hart arrived from California, and soon began planting conifers (cone-bearing trees) and deciduous ornamental trees as shelter for the village and Power Station staff. A tree enthusiast, he was familiar with many different conifers and their preferred environment in California and was encouraged by the local conditions. In 1933 he received permission to plant groups of pine species and other conifers into an experimental plot on the south-facing hillside just east of the penstocks, using stock raised by local nurseries, and from imported seeds. This allowed him to study the trees’ natural growth habit in detail, and to learn which species might do well in the Lake Coleridge catchment, and for New Zealand generally. He was superintendent for 30 years so there was time to make regular notes and measurements – helped, it was said, by the local schoolchildren who climbed the young trees to measure their height. Trees were also planted later for firewood, and in the 1930s and ’40s when horses and drays (horse-drawn wagons) were still used, every household in the village was allocated two full drays of firewood for the winter each year.
Mr Hart continued to add more trees and shrubs to the collection for years after his retirement. Nearly a century after the first plantings it has been described as one of the best mature conifer collections in the country (and a valuable seed bank) and one of the most diverse conifer collections in the southern hemisphere. There are more than 140 kinds of trees, including cedar, fir, Coast Redwood, Wellingtonia, spruce and hemlock; examples of over two thirds of the world’s 111 known pine species; rare Asian and North American conifers added in 1985, and more recent plantings. The 1.95-hectare arboretum is now a shady forest environment with natural seedling regeneration, while the village trees have a more open park-like feel and spectacular autumn colour. The arboretum is now also part of Te Araroa National Walkway, and a ‘Tree Trail’ network of tracks winds up through the forest, very soft underfoot because of the thick layer of fallen
needles which also creates a strangely muffled soundscape. Star Wars fans may discover an echo of the forest moon of Endor (and possibly supply their own sound effects); wine experts can expect to find those elusive hints of ‘forest floor’ and ‘wet stone’! The arboretum is managed primarily by the Central Canterbury Farm Forestry Association Arboretum Trust, along with Selwyn District Council and Trustpower (who owns the land); most development and maintenance is done by volunteers from the local community, supported by Council and Trustpower.
The collection was planted to observe the trees’ natural growth habit, and to let them form their own environment, so that (with a very few exceptions) they’re not pruned up with clean trunks as in a plantation woodlot, or shaped to a pleasing outline as expected in a public park or botanic garden. Dangerous or badly snow-damaged limbs are removed (local arborists use the annual process for training purposes), but otherwise the trees have been left to their own devices; and allowing for their age they’re naturally somewhat feral and shaggy as a consequence. Managed pine plantations higher up above the village and surrounding the arboretum are quite a contrast in appearance. Ongoing identification work has made it easier to find the different species using a weatherproof brochure available at the entrance, or by checking for labels near the trunks.
Surrounded by tall peaks and quite close to the Main Divide, the local climate of Lake Coleridge and the arboretum is significantly different than out on the open plains. Precipitation (including snow) is spread more evenly through the year, and is usually around 1.5 m, more than double that of Christchurch or Ashburton. The trees have generally appreciated the conditions and contributed to their own success – increased shelter, shade and protection around the village and arboretum make for cooler temperatures in the summer, and relatively milder conditions overall in winter. There are more recent plantings too at the arboretum extension, including the rare Australian Wollemi pine Wollemia nobilis (closely related to kauri) in 2014. Mr Hart would surely be delighted that his cherished trees are cared for and a real focus of interest - along with the station, still powering on as a fully functioning part of New Zealand’s industrial heritage.
Nearly a century after the first plantings it has been described as one of the best mature conifer
collections in the country.