The miracle of growth
In the spring, the northern forests come to life. Pine seeds spread with the wind and germinate quickly. During the summer, pine seedlings grow rapidly, taking advantage of the bright days.
In early summer, pine seedling stretches to a length of 2–3 centimeters per day at best. Thickness growth is most intense in late summer. A light spring tree grows first on the outer edge of the trout, which turns into a dark summer tree at the end of thick growth.
Quality pines are maintained throughout the rotation period
To grow a quality log the forest must be maintained throughout its rotation period. In five years, the pines have grown to a height of one metre. Among them grow deciduous trees, such as birches, rowans and aspens.
After an early clearing, at approximately 15 years, the sapling stand will be thinned out to the correct growth density. Ten years later, it will be time for the first thinning, during which the highest quality trees are left to grow. After this, the forest will be thinned out once or twice more and potentially fertilised before a regeneration felling.
Breeding leads to more growth and higher quality
In Finland, the desire to preserve and develop the genetic makeup of the highest quality trees started in the 1940s. In the decades that followed, the pioneers of forest breeding selected more than 7,000 healthy, high-quality pines with excellent growth properties from around the country.
These so-called plus pines formed the foundation of Finnish pine breeding. Their genetic makeup was propagated to seed plantations through grafting, and the resulting seed was used for forest cultivation. Later, the plus trees with the best offspring were crossbred to transfer their beneficial genetic material to their offspring.
Through determined breeding work, forest researchers have been able to significantly improve the quality of pine trunks, and optimise the branch diameter, angle habits and growth.
The branches of the improved pines are thinner and easy to prune. This increases the proportion of the trunk’s most valuable part, the branchless butt log, and therefore also the amount of branchless sawn timber that can be achieved.
On average improved pines grow 20 per cent faster than other pines. Even the climate benefits from the improved growth, as improved trees absorb more carbon dioxide from the atmosphere.
The breeding work to improve the growth speed, the quality and durability of pine is ongoing. As a result of selective breeding, the profitable genes will concentrate and multiply the benefits in each tree generation.
Heartwood extractives protect against decay
In midwinter, temperatures in Finland can fall to minus 30–40 degrees Celsius. For many species winter is a trial, but pines have adapted to it genetically. In fact, the pine is able to withstand temperatures as cold as minus 70 degrees Celsius.
In a pine stand ready for regeneration, the tree crowns can reach a height of 30 metres, with their diameter at chest height being around 25 centimetres.
Heartwood has formed at the core of the pine. This dense and dark wood is naturally resistant to decay due to its extractives. In mature pines, more than half of the trunk’s volume can be heartwood.
The versatility of pine is unparalleled
As raw material for sawn timber, the versatility of pine is unparalleled. One regeneration-ready trunk can be turned into a branchless butt log, butt logs with few branches, middle logs with dry branches and top logs with fresh branches.
Taking into account the various factors – such as quality, dimension, length, moisture content and sawing method it is possible to produce up to 60 different sawn timber products from one log.
The final end uses of sawn timber are determined by the parts of the log. Sawn timber made from butt logs is usually refined into glulam beams and posts for construction projects, where strong and stiff materials are required.
Middle logs are used by manufacturers of timber houses and door and window components. The long, regular knot frequency is well suited to the finger joints used in frames and semi-finished products.
Top logs with healthy branches are perfect for visually demanding locations. They are refined into internal and external cladding panels and glulam for furniture.
Northern pine plays an important role in building a fossil-free future.
Discover the characteristics of Nordic conifer.
This article was originally published in Fibre Magazine issue 2025.