draw. Stanisław Spława-Neyman
Look at the birch bark’s white glow
As if it slept in the sheets of snow
On bark that is so paper-white
Maybe a poem of birch I write?
Or read like a musician, before long,
The little notes of a nightingale’s song
Trade names and regional names:
brzoza (Poland), Bouleau commun (France), Abedul (Spain), Berken (the Netherlands), gemeine Birke, Wiessbirke (Germany), Björk (Sweden), Common birch (the United Kingdom), Betula bianca (Italy)
- phylum - Angiospermatophyta - angiosperms,
- class - Dicotyledonopsida - dicotyledons,
- family - Betulaceae - the birch family,
- genus - Betula - birch,
- species - Betula verrucosa Ehrh. - European white birch, common birch.
Betula lenta L., Betula lutea Michx. f., Betulapubescens Ehrh., Betula spp.
Birch (Betula verrucosa Ehrh.)
photo: Stanisław Spława-Neyman
Birch is an important forest-making species. Around the world there are 120 birch species, in the northern hemisphere are 40 species, 7 species exist in Poland. In Poland the most widespread species is the common birch (Betula verrucosa Ehrh.). Silver birch is the other name that is often used. Under favorable conditions the tree can reach a height of 30 m and breast height diameter of 80 cm. The biggest and the oldest recorded specimen of birch grows in Gdansk-Oliwa, it is 171 years old and it reached the height of 26 m and breast height diameter of 102 cm (321 cm in circumference).
The natural range of European white birch covers almost all Europe with the exception of Spain, Greece and the northern foreland of Italy. In addition, it occurs in a part of Asia Minor, in the Caucasus and in western Siberia. The range reaches the 65° parallel of latitude to the north, but it is not as far north as the range of a similar species – pubescent birch. Birch does not appear in the high parts of mountains, in general it can be found up to 700-800 m above sea level. In the Tatra Mountains individual specimen may occur at heights up to 1480 m above sea level, and in the Alps even up to 2000 m above sea level. Birch is a species considered as pioneering, quick-growing and resistant to industrial pollution. This species yields a crop as early as the 10th year of life (in pure stands), when grown densely in the 24th-25th year. It fructifies every year, every 2-3 years it is more abundant in seed than usual. It blossoms in April. The fruits – nutlets with a wing – are up to 2 cm long. Germination ability of fresh seeds is 60%, after they are stored it is only 20% in spring. Very light fruits are carried by the wind, sometimes they cover considerable distances. As a dominating species in Poland’s forests birch covers an area of 5,4%. Compact wood (large timber) volume per 1 hectare is 140,6 m3 and biomass – 113,1 t/hectare.
The percentage share of birch covered area in particular regions is as follows: I – the Baltic Region - 6,4%, II – Masuria&Podlasie Region - 9,2 %, III – Great Poland&Pomerania Region - 3,2%, IV – Mazovia&Podlasie Region - 7,6%, V – Silesia Region - 4,9%, VI – Little Poland Region - 5,0%, VII – the Sudetes Region - 6,0%, VIII – the Carpathians Region - 1,8%. Furthermore, black birch (Betula obscura A.Kotula) exists in southern and western Poland. The tree can reach a height of 15 m. While the (Betula oycoviensis Bees.) birch is predominantly a shrub under protection. Pubescent birch (Betula pubescens) is only a little shorter than common birch. The former species grows all over Poland; it favours damp, boggy areas. Both species occur together, crossbreed and the crossbreds are something halfway between the original species. Betula carpatica is a mountain species, it grows in the Tatra Mountains and the Sudetes in the form of a shrub or small tree up to 6 m high. Low birch (Betula humilisSCHRENK) is a shrub up to 2 m high. In Poland this species can be found solely on peat bogs. It is a postglacial relict. Dwarf birch (Betula nana L.) a shrub up to 80 cm high, grows solely on peat bogs and like Betula humilis is a postglacial relict.
Tree and wood characteristics
A quick-growing monoecious tree reaching a height of up to 25 m with a diameter of up to around 60 cm; often also in a dwarfish form. The bole is clean for up to around 12-15 m, cylindrical, sometimes deformed at the butt; on unfavorable sites also crooked. At the age of 60-80 years the growth of the tree stops. The maximum age is between 100-120 years. The bark is milky white, can be ripped away crosswise in thin strips, with age it becomes motley in color, cracked, thick and blackish. The bark share is around 12%, density is 562 kg/m 3 . Sapwood and heartwood do not differ. The wood is yellowish-white to reddish-white, practically without heartwood, bright in appearance, it has pith flecks in the inner belt of the bole; similar to alder. Annual rings are faint. The wood pattern is diverse: from plain to striped, “flames-like”, to a very ornamental, while especially beautifully patterned wood comes from Sweden and Finland. The homogenous structure, often characterized by grain corrugation, is fine, tiny and even. It is not distinguished by smell. The wood is medium weight, not very tough, strong, elastic, ductile, and easy to bend.
Machining both hand-working and machining - good and easy with all kinds of tools; a hard-fissile wood; good for processing by means of turning, slicing and rotary cutting.
Drying good; As the wood shows considerable tendency for cracking and distorting, the process of drying should be conducted carefully and slowly.
Gluing good; diverse susceptibility to gluing with glues based on urea and phenol resins should be associated with the changing content of fatty substances which migrate towards the surface during drying.
Surface processing very good; planed surfaces are very smooth, have a beautiful gloss, are easy to stain, polish and lacquer; damage to lacquered surfaces may occur when polyester lacquers are used.
Other: inappropriate vaporization leads to yellow and red changes of color; wood resistant to acids; wood sometimes biologically active – possibility of skin inflammations (Dermatitis); sometimes it turns livid as a result of metal corrosion.
(Betuta verrucosa Ehrh.)
photo. Piotr Neyman
Birch (Betula verrucosa Ehrh.)
photo. Stanisław Spława-Neyman
Wood disadvantages: crookedness, non-cylindrical, if it appears the heartwood is dark (so called "false heartwood"), pith flecks, changes of color caused by oxidization, frost cracks, decay, changes of color caused by fungal attack, borer holes.
Toughness low; wood susceptible to fungal and insect attack, goes doaty very quick, not resistant to atmospheric conditions.
Application veneers; mostly in peeled veneers for interior and exterior use and plywood production; wood for furniture, claddings and parquet; especially suitable for the production of pulp and paper, particleboards and fibreboards, sports equipment, airplanes, boxes, reels, spiles, wooden nails, handles; suitable for turning and woodcarving.
Instructions: recommendations – winter felling, thick debarking, rip-sawing together with bark, sprinkling or ponding. Stack timber in an airy manner, using thin sticks, protect from direct sun, use end protection. Birch wood can be plasticized and thickened to different degrees in pressure tests with the use of ammonia. It can also be modified using synthetic resins.
Anatomical features: libriform fibres, single vascular tracheids and fibrous tracheids, tracheae – diffused (diffuse-porous species); vessels occur in pairs and in radial groups, longitudinal parenchyma - apotrachea-diffused type.
Physical properties: density of an absolutely dry wood - 460-610-800 kg/m3, density at 12-15% moisture content - 510-650-830 kg/m3, density after fell - 800-850-900 kg/m3, shrinkage: longitudinal shrinkage - 0,6%, radial shrinkage - around 5,3%, tangential shrinkage - around 7,8%, volumetric shrinkage - 13,7-14,2%.
Mechanical properties: bending strength - 76-147-155 MPa, modulus of elasticity - 14 500-16 500 MPa, compression strength - 38-51-100 MPa, longitudinal tensile strength - 35-137-270 MPa, perpendicular tensile strength - ok. 7,0 MPa, toughness 4,5-10,0-13,0 J/cm2, shearing strength - 12-14,5 MPa, perpendicular Brinell hardness - 22-49 MPa, attrition (oak:birch) 0,6:1.
Birch, birch grove is a very Polish tree. It grows all over Poland, hence so many places derive their names from birch (in Polish: brzoza), for instance Brzeźno, Brzoza, Brzeżany. In the words of the famous Polish writer Władysław Reymont “... it is donned in white plain dress and all enveloped in green unbraided plaits, and so pure and trembling it is as a girl awaiting the first Holy Communion”. Birch is a tree that is “good, merciful and it weeps and the whiteness is so visible from a distance”.
For a long time birch twigs have been a compulsory element of alters’ decorations prepared for the religious ceremonies of the Sending on of the Holy Ghost to the Apostles and Corpus Christi. It has been considered the tree of joy for ages. There is an old tradition which originates in the early Christian period to becomingly welcome The Holy Ghost descending from heaven to human dwellings.
Knowledge of the benefits which can be obtained from birch is passed on to further generations. And so, birch leaves are sometimes used in medicine. Birch sap was considered a medicine and it was applied to wounds. Birch bark is used in tanning. Smooth white birch bark called “brzosta” in Polish is used for the production of wood tar – a greenish, opalescent substance obtained during destructive wood distillation – a world-famous Polish product. At the beginning of the XVIIth century Poles set up a factory for this specific product in America along with the first glassworks, first soap manufacturing plant, first sawmills and first boat builder’s plant. Birch sap, called“oskoła” in Polish, is used for the production of beer, vinegar, sparkling wine and syrup in the northern countries. Birch wood attacked by dipterous insects is characterized by swellings, and irregularity of structure; which is precisely what is so commonly known as “burl”. This burl was popular in the XIXth and at the beginning of the XXth century. To the present day handles of the famous bowie knives, the most expensive ones are called "Lappin leuku", are made of birch burl.
Nowadays we can observe the renaissance of birch as a “friendly” tree. Recommendations to go the forest and embrace a birch – which will have a positive influence on our health – have been known for a long, long time. In the XIXth century people still believed, according to Mazurian beliefs, that the best way to fight a shiver is to go to the birch forest, shake a definite number of birch trees one after another (most often 3 or 9) and say “shake less than I shake you, and then stop”. As you can see “nihil novi sub sole”!
A study prepared by:
asst. prof. PhD (Eng) Stanisław Spława-Neyman,
(Eng) Zofia Owczarzak