Peter Donaldson in the Himalayas. Photo: Dan Novak
HE WAS Charles Darwin's close friend, a great English botanist and the namer of more than 10,000 plants. Joseph Hooker (1817-1911) has gone down in the history books for his astute observations about how plants are distributed around the world. But former scientist, documentary filmmaker and gardener Peter Donaldson has found Hooker's research has new relevance, particularly when it comes to the effects of climate change. Donaldson, who has spent the past five years traversing the world to visit places Hooker explored - the Himalayas, the sub-Antarctic, New Zealand, Tasmania, Morocco and more - says Hooker is a great example of ''what good science is about''.
''That plants are affected by climate doesn't sound much these days but, at a time when people felt plants were put around the world by creation and that there was no relationship between them, it was a big thing to come up with his views about how plants migrated around the world,'' Donaldson says.
While Hooker deduced that arctic plants had moved north as the world had heated up and then become marooned on isolated mountains, he surmised that the pathway for plant movement across the southern hemisphere had been a great southern land (and this was a century before Gondwana was first mooted).
Hooker's Rhododendron hodgsonii. Photo: Peter Donaldson
Just as Hooker discovered tough, low-lying snow rhododendrons (Rhododendron nivale) that had worked their way up wind-battered, snow-covered Himalayan mountains to find a climate cold enough to suit, he was the first to spot that species of the southern beech tree (Nothofagus) were scattered from South America to Australia to New Zealand. It was he who detected the same grasses growing in isolated, wide-apart southern hemisphere locales and who became intrigued as to how African plants were related to those of Europe.
Donaldson lives in Bowral in the southern highlands of New South Wales and became curious about the Suffolk-born Hooker when, while researching Mount Kangchenjunga in the Himalayas for another project, he found the botanist's name repeatedly popping up. Hooker was the first European to collect plants in the area and discovered more than 20 species of Himalayan rhododendron.
Donaldson abandoned his original Mount Kangchenjunga idea and armed himself with copies of Hooker's letters, journals and sketches, then filmed himself retracing Hooker's Himalayan explorations. After that 350-kilometre trek, he felt the urge to continue: ''If I wanted to describe Hooker's importance to botany, I had to explore his relationship with Darwin [with whom he exchanged more than 1400 letters] and the other influences on him.''
A key influence was Hooker's time as assistant surgeon (he had trained as a doctor) and then as, in essence, the naturalist on an Antarctic expedition from 1839 to 1843.
''He was an incredible list-maker and the breadth of his knowledge of plants allowed him to see patterns,'' Donaldson says. ''He could look at a particular plant on one side of the world and remember where it was located on the other.''
Hooker had been given a good grounding for this. His father (the first official director of the Royal Botanical Gardens, Kew, with Hooker himself the second) had first made a name for the massive size of his herbarium, which contained about 1 million dried plant specimens.
So Hooker knew a new plant when he saw one, and added thousands of Antarctic and, later, Himalayan specimens to Kew's plant collections. The new species of Himalayan rhododendrons were among his great discoveries. He sent back to England sketches, dried specimens and seeds, and these rhododendrons began to be planted in some of the country's grandest gardens. The baroque Castle Howard still has them growing in the garden and, closer to home, some Hooker species are at the National Rhododendron Gardens in Olinda.
Not so spectacular but still curious is the megaherb Pleurophyllum speciosum that Hooker collected from Campbell Island, 700 kilometres south of New Zealand. While attempts have been made to grow this daisy in botanical gardens in mainland New Zealand, Donaldson says it is ''always a struggle'' as they need a constant cold, coastal climate to survive.
Which begs the question about what will happen to plants such as this as temperatures increase. While Donaldson found the daisy on the island, he suspects it no longer grows in all the spots where Hooker found it. ''I believe climate change will have an impact on plants,'' he says. ''If you look at the Snowy Mountains in Australia, for example, where are alpine plants going to go in a warming climate?''
■ Peter Donaldson delivers his illustrated lecture, ''Botanical trailblazer: Joseph Hooker the unknown hero of evolution'', at Mueller Hall, Birdwood Avenue, Royal Botanic Gardens at 6.30pm on February 22. It is presented by the Australian Garden History Society; registrations essential. See gardenhistorysociety.org.au.