Final answer:
The ideal time to prune non-flowering trees is during the late winter or early spring before the onset of new growth. This practice aligns with the trees' natural dormancy and minimizes disease and pest risks.
Step-by-step explanation:
The best time to prune non-flowering trees is during the late winter or early spring before new growth starts. This timing is crucial because it allows trees to heal without the stress of extreme cold or the energy demands of producing new growth. Pruning during the dormant season minimizes the risk of pest infestation and disease, as there are fewer active pathogens and pests. Furthermore, without leaves on deciduous trees, the structure of the tree is more visible, making it easier to identify which branches to remove. Pruning when there is no foliage also prevents the spread of diseases that are active during the warmer temperatures.
Pruning at the correct time supports the tree's natural life cycle, as many species require a certain amount of cold, or 'chill time', before they can break dormancy, as noted in studies of shoot apical meristems in apple trees and other species. In fact, cooler temperatures are crucial for many plants not only for pruning purposes but also for the timing of flowering and other growth processes—demonstrating the intricate balance between plant physiology and environmental cues.