Improved Sitka spruce trees are those grown from seeds that have been selected because of desirable characteristics of their lineage – such as fast growth rates, timber density, straightness, stiffness and low incidence of knots.

Improved Sitka stock can produce significantly greater yields of timber per hectare. Research has found there is up to 29% increase in volumes of high quality green logs and sawn timber, due in part to more trees surviving to maturity and more logs available from each tree.

A recent study investigating the impact on quality found the benefits of Improved Sitka were most significant in terms of the increase in the proportion of high-quality “green” logs and timber that was achieved.

The objective of tree breeders through the first generation of selection and testing of Sitka Spruce has been to maximise growth rate and stem straightness, whilst minimising the loss of wood density.

Recent studies have endorsed research findings published in 1992 by the Building Research Establishment (UK), which found that trees selected for a relatively faster growth rate (up to five to ten years) but with well above average stem straightness and reduced knot-to-surface ratio, will show no significant decrease in construction-grade pass rates at the sawmill. This means the material will be available for construction use as C16 and C24 strength-structured timber. The result is that more construction-grade timber can be grown from the same area of land.

To read more go to www.forestresearch.gov.uk and write in FCRN003 to search engine on site.

Read about the Native Woodland Scheme.