Abstract <p>Stem sinuosity, a growth deformity, reduces timber value, thereby reducing the benefits of fertilization. This study examined the relationship between nutrient deficiency and stem sinuosity for fertilized western hemlock (<i>Tsuga heterophylla</i> (Raf.) Sarg.) on northern Vancouver Island. The site was fertilized at planting (1988; 10&#xa0;g N, 2.5&#xa0;g P, and 5&#xa0;g&#xa0;K per seedling), in 1993 (255 N kg ha⁻¹ + 75 P kg ha⁻¹), and 2004 (255 N kg ha⁻¹), respectively. Foliar samples were analyzed from three groups: 1) fertilized sinuous, 2) fertilized non-sinuous, and 3) unfertilized control (non-sinuous). Fertilized western hemlock had lower nitrogen, potassium (K), and zinc (Zn) concentration levels than the unfertilized control. However, there was no distinct difference in nutrient concentrations between sinuous vs.&#xa0;non-sinuous trees. On the other hand, although individual nutrient trends were insignificant and inconsistent, classification tree analysis may show the potential involvement of multiple nutrients for trees exhibiting sinuosity: sinuous western hemlock trees tended to contain lower levels of K and sulfate simultaneously than the other groups. Therefore, these findings suggested that further research into the potential roles of K, Zn, and sulfate in influencing stem sinuosity in western hemlock, particularly in the context of fertilization, is warranted.</p> Study Implications <p>The findings highlight that fertilization may inadvertently contribute to western hemlock stem sinuosity, despite beneficial growth, under specific nutrient imbalances. The observed association between lower potassium (K), zinc (Zn), and sulfate levels and stem sinuosity suggests a need for further research into the underlying mechanisms. In particular, future studies should examine the interactions between nutrient dynamics and other environmental factors affecting to stem form variation in western hemlock.</p>