There are nine birch trails planted in GB: 6 in Scotland, 1 in England and 2 in Wales. In addition there is a trial of similar material in Ireland.
The trials were established in two series. The oldest series of trials was planted in 1997 – 1999 and contains provenances collected in Scotland and northern England. The distribution of the provenances are shown on the map below:
Birch planting trial and seed collection sites in Scotland and north east England (960px by 1387px, 174K - zoom map to view full size)
The most recent series of trials was established in 2003. This later series of trials contains provenances from across Britain plus some continental material for comparison. Some provenances were used in both sets of trials. The GB distribution of all provenances and the locations of the trials are shown on the map below:.
Birch provenance locations and experiment sites (760px by 1126px, 124K - zoom map to view full size)
These show that the more southerly provenances are growing more vigorously than the local material and in some cases the differences are of the order of 80% greater height growth by year six. This is possibly due to the longer period that the southern provenances grow each year.
Of the local provenances, the lower elevation ones are outperforming the higher elevation examples. A note of caution must be advised since the trial is still young and some extreme weather could alter the results in the long term.
This work is being undertaken with the Birch Group of the British and Irish Hardwoods Improvement Programme.