Choice of silver birch planting stock for productive woodands

Silver birch is second only to oak in terms of total broadleaved woodland area in Britain. In the last two decades there has been an increase in the planting of birch woodlands both for timber production and the creation of native woodlands. The GB map of Native Seed Zones and Regions of Provenance provides guidance to managers wishing to source suitable local stock when creating native woodlands, but is the local seed zone the most suitable planting stock when timber production is the objective? This Research Note presents an analysis of early-height data involving 58 silver birch provenances collected from woodlands all over Britain and the near continent, and then planted in replicated trials on eight sites in the UK. Analysis of the early height data suggests that when timber production is the objective, for which early height growth is taken as a surrogate, then local seed sources are rarely optimal. Managers interested in optimising financial return could consider planting stock from at least 2° latitude south without suffering any detrimental effect on over-all survival or increased frost-risk. The benefit of planting more southerly-based stock varied from between 24 cm and 55 cm for each degree of latitude. Managers need to be confident that the silver birch planting stock they plant now, will perform satisfactorily over the next 30–60 years and so selection now of more southerly material offers growers a potential opportunity to ‘future proof’ their planting choices.