Poplar clones in Northern Europe respond differently to climate and daylight, affecting their growth. Warmer temperatures make trees bud earlier but shorten the growing season. Clones at different latitudes also show varied growth patterns. A model based on growing degree days can predict how clones will perform in different climates, helping to rank them for optimal growth. While predicting exact timing of growth stages is tricky, ranking clones based on observations can guide their selection for different regions and climates.