When we think about the typical lifecycle of plants such as garden flowers, it seems quite simple. A plant grows from seed, produces flowers then fruits or seeds before eventually dying.
The next growing season, a new plant emerges from the new seed and the cycle begins again. With trees and other longer-lived plant species, the lifecycle takes more time, but the process is essentially the same.
Imagine then, a plant that for tens of thousands of years has never born fruit yet somehow keeps itself alive, reproducing itself via cloning, so that the plants we see today are genetically identical to what they were over 43 millennia ago. Essentially, it's the same plant. That's the story of King's holly (Lomatia tasmanica), a small, shrubby tree 2-8m tall that lives near creeks in the rainforests in southwest Tasmania. It is one of the world's oldest clonal plants.
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Though King's holly has glossy pinnate (feather-shaped) leaves with slightly spiked edges, it is no relation to the holly trees we associate with Christmas (genus Ilex). It occasionally produces flourishes of curled, purple-red flowers, but it makes no seeds or fruits – and certainly no red berries.
King's holly was only discovered in the 20th century. Tin miner and (fortunately) plant expert Charles Denison King was prospecting in the foothills of the Bathurst range in southwest Tasmania in 1934 when he came across a colony of plants that he recognised as an unusual Lomatia species.
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He found a second colony in the mid 1960s and was so curious, he sent a sample to botanist Winifred Curtis at the University of Tasmania. She confirmed it as a new species in 1967 and called it Lomatia tasmanica though gave it its popular name after its discoverer.
Further genetic studies showed that instead of the usual pairs of chromosomes that carry the reproductive genes, King's holly's chromosomes came in threes (known as a triploid). This means that despite producing flowers, the plant's chromosomes cannot match with a partner in order to reproduce and so it is sterile. Instead, the plant spreads either through its root system, sending up new growth, or when a branch drops to the group and establishes roots, creating a new plant that is genetically identical to the original.
In 1989, University of Tasmania plant biologist Greg Jordan found fossilised leaf fragments of King's holly, which dated to 43,600 years ago but possibly as old as 135,000 years. And the fossil was exactly the same plant as those living today. Studies have found that individual King's holly plants commonly live to be 300 years old and grow at an extremely slow rate, just 2.6mm a year.
Despite its hardiness, longevity and ability to keep cloning itself, King's holly's status in the wild is precarious. The second colony found by King has subsequently disappeared, possibly destroyed by forest fire, while the first colony is confined to a 1km-long strip of land containing just 300 plants. Fortunately a new colony was discovered this year though its location is being kept secret to prevent visitors damaging the plants or introducing a pathogen called Phytophthora cinnamomi, which can kill King's holly.
To help with the plant's conservation, botanists have attempted to propagate it in captivity, with limited success. Cuttings take up to 12 months to produce roots and are very difficult to keep alive. However, spurred on by the need to protect this extraordinary plant, botanists' success rates are improving and an Australian nursery has been given approval to propagate King's holly – though not for commercial purposes.
Despite its 43,600-year existence, King's holly may not be the oldest cloned plant on Earth. That label may belong to Pando, a colony of 40,000 aspen trees in Utah, USA. These are essentially offshoots from one tree, are all genetically identical, and the entire organism might be as much as 80,000 years old. Pando is Latin for 'I spread'!
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