Black Poplar (Populus nigra)
Family: Willow plants
Genus: Poplars (Populus)
Section: Cottonwood (Aegiros)
The tree of the year in Germany is annually chosen by the Kuratorium "Baum des Jahres" (site available in German only).
It stands there with its canopy nearly as broad as high, its wide overhanging branches and big, already at slight wind extraordinarily fluttering leaves: The European black poplar. It got its name by the impressive black bark which comes into its own especially at old instances generically.
Worldwide there are 60 different poplar species. Why was the European black poplar of all trees, which is resident at riparian zones, selected to be the tree of the year 2006? Because it has become rare, so rare that it is in the Red List of endangered plant species. The reasons are diverse: First of all, drawdowns and the clearing of natural riparian zones by the human destroy the habitat of the impressive tree which can age up to 300 years. Moreover other, not domestic poplars which grow even faster or the crossing especially with aspens are often used. So comes that older, pure black poplars are already a little sensation. They are therefore in several European countries and several German federal states filed and mapped.
Old black poplars are of mighty, gnarled growth and normally age 60 to 80 years, in exceptions up to 200 and rarely even 300 years. The biggest instances can achieve a stem diameter of far over two meters and under good conditions a height of 30 meters. The bark is normally black with rude reticular structure and transverse cork beads. Sometimes water sprouts and burls establish, which can form weird stem forms. The overhanging crowns of the European black poplar are nearly as broad as high and partially erratic. Generic for the tree of the year 2006 are also the upstanding fine slips. The buds are very long-drawn-out and pointed, the leaves have a rhombic shape with long, extracted peaks which are at a ca. eight centimeter long stalk that is compressed laterally.
By the ribbonlike stalks, the leaves can flutter in the wind flexibly. But even the weird fluttering of the leaves in the wind serves a purpose: The movement of the air cools the leaves and the evaporation is promoted thereby, so that the current of water from the roots with the there dissolved nutrients is accelerated. This eventually leads to an increase of the growth. The trick with the leaves fluttering in the wind however brings another advantage: The 'movable' leaves also let more light come through into the inside of the crown, what again positively influences the growth. Recognizing the black poplar by its leaves is hardly possible as the leaf shape is very variable and consequently isn't a certain distinguishing characteristic. In april before the foliation, the tree sprouts ca. ten centimeters long inconspicuous catkins. Already with ten years a poplar can blossom, however a black poplar either has only male, reddish or only female, yellow-green blossoms. Species where the male and female blossoms can only be found on separate individuals, are called dioecious.
In the end of May or beginning of June the fruits of this tree species are ripe, which grow in capsules at the tree and then pop. Fluffy encapsulated seeds fall out, which the wind often spreads over kilometers. Interesting is that the poplar fluff recently also finds a use as badding of pillows and blanket as well as as insulating material. Surprisingly, the fibres of the black poplars keep as warm as down, but forward the moisture much better and faster. It is proven that no textile material has a better combination between lightness, insulation and humidity behaviour than poplar fluff. The roots offer the tree of the year only partly foothold as shoreline stabilization as they don't grow under the middle groundwater line. The buttress roots of the poplar mostly diffuse very far from the stem in the topsoil area.
Because black poplars almost solely are native in natural softwood meadows, they have perfectly adapted themselves to that environment and master some subtle tricks as for example the vegetative regrowth: Poplar branches are naturally very fragile, even when they aren't dead yet at the tree. The vegetative regrowth only works at summer period, when the poplars still have their foliage: Even without slight wind, some branches of the poplar tree break and drop onto the ground. Because of the green foliage at the branch, it is slightly decelerated, like with a parachute, so that the lower end of the branch, which broke from the tree, impinges on the ground first and bores ento the moist, loose softwood meadow ground with its drop power. There the branch forms already after relatively short time fine roots and is able to provide for itself, whereby a new sapling has emerged.
The poplar is a deciduous tree species with discoloured heartwood, which has very high, narrow medullary rays. You will never find a colour heart, just as oaks or pines have it, at a black poplar. That's why the wood of the poplar trees is usually uninteresting or even boring for the spectator, as it has hardly got a grain. It should be added that the poplar wood only has a bad quality, so that it neither finds a use in timber- and firewood production nor in manufacturing of furniture, at best as base timber. Therefore it is very popular for the production of paper, matches, splint baskets, chipboards and as feedstock for cutting sculptures.
Energy wood plantations also have a promising future with the fast-growing black poplar, which would be binding carbon dioxide from the atmosphere as a positive side effect as well. Moreover soils poisoned with heavy metals can be detoxicated again by the planting of poplar trees. Consequently the black poplar is also a bioindicator for the proof of environmental pollutions. In the naturopathy you can retrieve the buds of the poplars as teas, antiphlogistic cremes and ointments as well as as medicinal spiritus and carbon. Already in the ancient world the black poplar was admired as a tree of grief and of the underworld. Already almost 2000 years ago, the Greek doctor Galenos recommended an ointment against inflammations made of the buds of the black poplar. Such ointments today still find a use as anodyne balm.
However, the fast growing plack poplar is not only at the human but also at the animals very appreciated: A large amount of insects lives on poplars - some of them specially on the black poplar, as for example the poplar hawkmoth. The trees are often inhabited by gall-producing insects, too; the poplar spiral gall aphid is thereby the insect species that can be found most. Its infestation causes a convoulted torsion and bulge of the leaf stalk. The gall which is typical for the spiral gall aphid is 20 millimeters long and 10 millimeters thick. Also beavers like young poplars, especially because the wood is very easy to chop down for them!
The soft wood is, however, an attractive habitat for rust fungi and many wood-subversive fungus species as well. Particularly one fungus (Cryptodiaporthe populea) has specialized in the rot sensitive poplars and evokes the so-called 'crown dying of the poplar' and the Dothichiza-frost canker. However this fungus afflicts preferentially weak poplars, which have for example populated the wrong habitat, have strong competition by neighbouring trees or were weakened by heavy winter frosts. Thereby through the fungi possibly more and more parts of the crown die back until the remaining crown parts can't nourish the tree any more and the tree finally dies back. Entire poplar forests were already destroyed by this fungus, particularly susceptible are pyramid-shapes and Italian poplars.
As already mentioned, poplar trees have the ability to yield green branches without discernible reasons (vegetative regrowth). That is why larger poplars should be unburdened urgently if they endanger the roadworthiness at a location open to the public. Because poplars do generally seal off against rot fungi very badly, they should absolutely only be cut by a skillful expert.
Incidence / Demands to Site
The tree of the year 2006 needs much light plus very good nutrient-rich and watery soils. Moreover black poplars populate preferentially well-aerated gravelly and sandy soils with groundwater connection. Because of its high location claims, the fastest-growing tree of moderate latitudes can almost only thrive in riverside forests directly at riverbanks, because it is a competition weak tree species. The black poplar is spread almost in all parts of Europe, ecxept in the north, because it has a certain heat requirement. Height increases of one meter per year aren't a scarity for the black poplar, provided the conditions are favourable. Regular, short floodings don't depict a danger for the tree of the year 2006 either, by more extended floodings the growing power is restricted distinctly though. For that reason, areas with ponding water are avoided by black poplars. By the ability to form new roots at the stem up until old age, black poplar trees also survive coverings without any problems. Even against injuries by flotsam or drift ice, this poplar species is specially well-equipped, so that they heal up quickly.