Incidence of autumn frost damage and lammas growth in a 4-year-old clonal trial of Sitka spruce (Picea sitchensis) in Britain

Summary The relationships between lammas growth, frost damage and early height growth in Sitka spruce (Picea sitchensis (Bong.) Carr.) were investigated using data from a 4-year-old clonal trial replicated over two sites in southern Scotland. The ability to produce lammas growth is an important component of early height growth in genetically improved Sitka spruce and could account for an average of 22 per cent of early height. Selecting clones exclusively for the ability to produce lammas growth marginally increased potential frost damage compared with unselected material, but there was no evidence to suggest increased frost damage with selection based on absolute height or current increment. It was concluded that selecting clones for total tree height would exploit the potential benefits of lammas and fixed growth, without increasing the risk of frost damage.