At what stage are conifers and other woody species easiest to kill?

The easiest stage to kill conifers and other woody species is when they are young with actively growing leaves. At this stage, these plants are in their optimal growth phase, which means they have a high metabolic rate and are more susceptible to herbicides. The presence of actively growing leaves allows for greater absorption and translocation of the herbicide throughout the plant, leading to a more effective kill.

Young plants are less resilient to stress and injury, and their cellular structures are still developing, making them less capable of recovering from damage. This vulnerability is particularly pronounced during the growing season, as the plants prioritize growth and energy investment in leaf and stem development.

During maturity or when leafless, woody species can withstand environmental stresses better, thus making them more challenging to control. Likewise, during winter dormancy, their metabolic processes slow significantly, reducing susceptibility to herbicides. Maximum height also correlates with maturity and generally a greater resilience to herbicide applications.