Treatability and Durability of Heartwood

Reduced treatability in heartwood can cause reduced retention and penetration of preservatives into heartwood. This can reduce the durability of heartwood compared to the treated sapwood. From an anatomical point of view, the factors which contribute to the lower treatability of heartwood include its high extractive content, high rate of aspirated pits, and smaller pore sizes. Generally, in wood members that consists of treated sapwood and untreated heartwood, the durability of treated sapwood is much higher. Untreated heartwood of southern pine, Douglas-fir, Englemann spruce, eastern spruce, red pine, white pine, eastern larch, eastern hemlock, and eastern fir lasts longer in outdoor exposure in the colder northern regions (Wisconsin and Maine) than in warmer southern regions (Mississippi). In the southern regions, the median life of the stakes for these species ranges from about two to four years with the exception of southern pine which ranges from about five to seven years. Eastern spruce and white pine appear to possess lower durability (about two to three years) among all the species studied. In the northern region, the median life of the species range from five to ten years with the exception of southern pine which lasts about eight to fifteen years.