Dienstag, 9. April 2013

Plant of the Day (April 9th, 2013) - Araucaria araucana (Molina) K. Koch

Today's “Plant of the Day” is a tree, which I planed to dedicate an own entry a long time ago but I didn't have enough pictures for a complete article. However, now I have and so, today's “Plant of the Day” is Araucaria araucana (Molina) K. Koch. The Genus of Araucaria is one of only three Genera within the family Araucariaceae. The other ones are Agathis (the largest genus) and the monotypic genus Wollemia (one species: Wollemia nobelis). All plants of the Araucariaceae are exotic conifers, which are native on the southern hemisphere. 

 A. araucana - habitus (young tree)
 
In German, A. araucana is known as “Chilenische Araukarie” or "Andentanne". In English, the species has many different names like “monkey tail tree” “Chilean pine” or “monkey puzzle tree”. In Spanish, the species name is “Pehuen” or “pienonero”.


A. araucana - bark

A. araucana is a large evergreen tree, which can reach a maximum height of nearly 40 metres (131.2 feet) in its native environment (however, the most individuals are between 8 and 15 metres (26.3 to 49.2 feet) high). The long stem has a smooth, grey bark with many round spots, which are the remains of older branches. The bark is very thick and protects the tree from fire caused by volcanic eruptions.
The branches are arranged in whorls with five branches per whorl. Young trees are branched to the ground, while grown-up trees only have branches at their tree crown. The whole crown has a characteristic pyramid-shape look.


A. araucana - branches

The hard leaves of A. araucana are triangular and scale-like. They have a leathery surface and a pointed apex. Thereby, branches are very sharp and can hurt you when hitting (trust me, I know what I'm talking about; it similar to a morning star ;-)). Leaves are arranged in a spiral leaf pattern and overlaps each other like roofing tiles (in Botany, such an overlapping is called imbricate). They have a dark green colour and are shiny. Stomata are on both sides; the leaves are amphistomatic.


A. araucana - leaves (ventral site

A. araucana is dioecious with male and female cones on different trees or monoecious with male and female trees at one tree. Male cones are upstanding and between 8 and 12 centimetres (3.2 to 4.7 inches) long and 5 centimetres (1.9 inches) broad. They spread their pollen during June but remain on the tree for months. They have a brown colour. Female cones are located at the end of the brnches. They are about 18 centimetres (7.1 inches) long and 20 centimetres (7.9 inches) broad. As you can see, they are more globular. Young cones have a golden yellow colour but become dark-brown during the ripening. When ripe, the cones break up and spread their seeds out. The seeds are bright brown and winged.


A. araucana - old male cone

The species is native to South America (Chile, Argentina) and grows in the Andes of South Chile and Patagonia. It has a very fine defined areal between 37° and 40° latitude and grows between 600 and 1600 metres (up to 5249 feet) altitude in mixed forest and pure stands. The whole tree is adapted to fire (thick bark, leathery leaves etc.), because there were and are many volcanoes in this area, which can cause bush fires. Because of its exotic habitus, A. araucana is also a very popular ornamental tree in Great Britain and Europe, where it's planted in parks and botanical gardens.


A. araucaria - leaves (ventral site) - please note the 
leaf-vein on the back and imbricate arrangement of the leaves

The wood is of high quality and was used to make houses, boats and bridges. However today, A. araucana is protected and it's not allowed to chop down trees any more, because strong logging had decimated the stock rapidly.

A. araucana is a living fossil and exists since the Cretaceous. However, the oldest, recent species of this family is Wollemia nobilis which exists since 90 Million years. This makes the Araucariaceae to one of the oldest tree-familes of the world.

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