[859][860][861][862][863][864][865][866][867]. The objective of this study was to define the optimum period for collecting sugar maple (Acer saccharum Marsh.) stem cuttings. In 1999 and 2000, shoot development was monitored on young trees from a plantation established in 1993. Stem base water content and the number of pairs of terminal bud scales changed over time, reflecting meteorological characteristics of both years. In 1999, rooting percentage was high regardless of collection date, within a 7-wk period. The 2000 rooting trial covered a longer time frame and identified an optimal window during which rooting percentages reached 60 to 83%. Rooting success dropped below 30% for cuttings harvested too early or too late. Thus the optimal time for collecting sugar maple cuttings spans several weeks, but with significant year-to-year variations. For both years, optimal rooting was associated with a stem base water content lower than 75% but higher than 55%, and with the presence of one to three pairs of apical bud scales. This stage is reached when at least 270 degree-days above 5°C are accumulated. Using these indicators, practitioners can consider local conditions and year-to-year climatic variations to harvest sugar maple cuttings at an optimum stage of development.