Earth is home to 3 trillion trees, with about 73,000 known species – and thousands more yet to be discovered. In this extract adapted from Remarkable Trees (Thames and Hudson Ltd, 2024), authors Christina Harrison and Tony Kirkham look at three truly amazing species, including one that can burn and blind people who touch its sap.
Manchineel
Hypomania mancinella
A member of the spurge family (Euphorbiaceae), this species actually holds the record as the most dangerous tree in the world. The milky sap of the manchineel, which drips from any wound on its trunk or branches, as with other spurges, contains strong irritants. It is so caustic that on contact with the skin, the liquid will immediately blister and burn, and can cause temporary blindness if it gets into the eyes. Even standing under this tree in the rain is dangerous, as droplets contaminated by the sap can have the same effects.
Native to tropical areas of North America (including Florida), the Caribbean, Central America, and northern South America, this evergreen tree grows up to 50 feet (15 meters) tall. It is found along beaches and coastlines, where its roots help prevent erosion. The fruits resemble small green apples, but they are also highly toxic and the tree has many common bad names, including the Spanish arbol de la muerte or manzanilla de la muerte – tree or apple of death.
Said to have a rather sweet taste, the flesh of the fruit, if eaten, soon results in severe burns and ulcers of the mouth and throat, leading to excruciating pain. Since all parts of the manchineel are toxic, local people sometimes mark the trunk of a tree with a red X or a sign to warn of its presence. The wood is used, carefully, in the production of furniture, but even burning it is dangerous as the smoke from the fire can cause serious eye problems.
Encounters with this species are mentioned by several famous explorers. The 18th-century naturalist Mark Catesby recorded the agony he suffered after the sap of the tree entered his eyes and that he was “for two days entirely deprived of his sight”. Manchineel’s infamous reputation also extends to literature – references are found in Madame Bovary and The Swiss Family Robinson, among others, while it also appears in operas, including Giacomo Meyerbeer’s L’Africaine, where it is cast as a means of suicide by the heroine Sélika.
Wollemi pine
Wollemia nobilis
On September 10, 1994, David Noble of New South Wales National Parks was walking alone in the remote and undisturbed sandstone gorges of Wollemi National Park in the Blue Mountains, just about 90 miles (150 kilometers) northwest of the largest city. of Australia, Sydney. . He came upon an unknown tree, of a very unusual appearance, which he had not seen before during his many walks in these wild canyons. After collecting a small sample of leaves, he took it back to the Royal Botanic Gardens in Sydney to be identified by the garden’s taxonomists.
It was a dramatic discovery that would surprise the plant world, as it was recognized as a new species of tree unknown to science. The tree was named later Wollemia nobilis, Wollemi pine. Wollemia, the genus, is named after Wollemi National Park, with the Aboriginal word “wollemi” meaning “look around you, keep your eyes open and be careful”; species name nobilis reflects the qualities of the tree and its discoverer, David Noble.
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The Wollemi pine is not a true pine at all and is a member of the very primitive Araucariaceae family, which was once abundant in the world’s forests during the Jurassic and Cretaceous period about 200 million to 65 million years ago. The other two genera represented in this family today are largely confined to the southern hemisphere – the kauri, Agathis, and the monkey enigma, Araucaria. The oldest known fossil associated with the Wollemi pine dates back to 90 million years ago, and it was assumed that the tree became extinct about two million years ago. Known only from the fossil record before its dramatic reappearance in 1994, it is a “Lazarus” or “living fossil” taxon.
Wollemia nobilis is a tall evergreen coniferous tree reaching up to 130 feet (40 m) in height, with a trunk diameter of about 4 feet (1.2 m). On mature trunks over 10 years old, the bark is distinct and has been described as bubbly chocolate. The tree’s unique branching habit means that it never produces lateral branches from the main framework of branches that grow outside the trunk.
Like its cousin the monkey puzzle, the foliage is spirally arranged and the leaves are flattened in two or four rows, making identification easy. During winter dormancy, the terminal buds are covered with a white resin known as “polar cap,” which protects the growing tips from damage by cold temperatures. This is thought to be one reason why this tree survived the ice ages. Once spring arrives, fresh, soft, lime-green foliage bursts through the canopy and begins to grow, gradually becoming a mature blue-green.
Two more small Wollemi pine trees have been found since the original discovery, although fewer than 100 mature specimens remain. Most have multiple trunks growing from the base, with some trees having up to a hundred. This natural climbing system may have evolved as a defense against fire and rockfall in the steep gorges where the tree naturally grows, also ensuring its survival to the present day.
However, it is also possible for trees to be clonal, and it has been shown that there is very little genetic variation between individuals.
Classified as critically endangered, the Wollemi pine is now protected in Australia and anyone found entering the remote canyon, whose exact location is kept secret, will be prosecuted. This penalty was implemented to prevent the introduction of a plant disease, an aggressive water mold (Phytophthora cinnamomi), which can cause major environmental damage to fragile plant populations when they slip into people’s shoes.
As part of the tree’s conservation strategy, young plants are cultivated and distributed or sold worldwide. At the Mount Tomah Botanical Garden in the Blue Mountains, an established planting of Wollemi pines grows in a fenced valley that mimics the trees’ natural home and protects the gene pool of this botanically fascinating tree. The Wollemi pine can rightly be called the dinosaur of the tree world and a living link to an ancient time. Perhaps if we had followed the Aboriginal meaning of the word wollemi, we could have rediscovered it much sooner.
Coco de mer
Lodoicea maldivica
Endemic to only two small islands in the Seychelles, the extraordinary coco de mer palm can only be found in the wild on a handful of sites in Praslin and Curieuse. Palms can grow between 82 and 165 feet (25 and 50 m) tall, with large, folded, fan-shaped leaves up to 33 feet (10 m) long. Its record-breaking fruits can weigh up to 40 kilograms and 1.6 feet (0.5 m) across, and these contain the largest and heaviest seed in the world.
These curious palms were once the stuff of myth and legend. Sailors believed they grew underwater at the bottom of the Indian Ocean, and male trees were thought to be uprooted on stormy nights and walk to find female trees, hugging them to pollinate their large flowers. People unlucky enough to witness such an event can be blinded or even die.
“Coco de mer” is French for sea coconut and the name may have arisen from people seeing the large seeds washed up on beaches or swimming in the surf, although the fruit is heavier than water and the seeds can only float when completely dry and empty. Also known as double coconuts, their rarity and suggestive rounded shape once made the seeds highly sought after and a valuable collector’s item.
The family and nobility treasured them in their cabinets of curiosities, often mounting them elaborately in gold. The trade in seeds is already closely controlled and they can only be sold with a permit, although illegal collection is a problem.
Although coco de mer has been widely studied, it still retains some mysteries and secrets. It is thought that the large size of the fruit and the seed it contains is a result of the geographical isolation of this palm – known as island gigantism. Normally, a parent plant’s strategy would be to disperse its seeds some distance, by wind or an animal, so that the offspring are not in direct competition for light and nutrients. But these seeds are so heavy that they fall close and grow in the shadow of their parent.
In fact, the soil here also contains more nutrients than further away, as the fan-shaped leaves of the mature palm are extremely effective at channeling water and transporting nutrients down the trunk to the soil at the base. As a result, clumps of coco de mer are created and they are usually the dominant species in the forests where they grow.
It is not yet understood exactly how the pollen from the “cats” of the 5-foot (1.5 m) tall male trees is transferred to the flowers of the female trees, the largest female inflorescence of any palm. Some believe bees are the agents, others think lizards may be involved. The seeds can take six or seven years to mature before they fall, and then longer before the cotyledon—the germinating sprout—appears. At about 13 feet (4 m) in length it is the longest known. This rope-like stem, nourished by the nutrient-packed seed, helps the young plant find the best place to plant its roots.
This exceptional palm is now under threat from harvesting, fires, introduced pests and human development. Although palm trees have been planted on several islands near where it grows naturally, the total population consists of only about 8,000 individuals, making this botanical phenomenon an endangered species.
Excerpted from ‘Notable Trees’ by Christina Harrison and Tony Kirkham, published by Thames & Hudson.