Red maple (Acer rubrum L. ‘Franksred’) and sugar maple (Acer saccharum Marsh. ‘Green Mountain’) trees were grown in a 56 liter (15 gal) pot-in-pot system for two years. During the second year of production, root growth was observed through observation plates fitted into the container sidewalls, and shoot extension was periodically measured. Root growth began in early March, approximately one month before budbreak for both species. Root growth dramatically slowed down at the onset of budbreak, but quickly resumed and was concurrent with shoot elongation. Root growth slowed dramatically in the fall when substrate temperatures dropped to 5–7C (40–45F). Root growth stopped during the winter for red maple, but some nominal root growth continued throughout the winter for sugar maple. Red maples had over 5 times more total root length against observation plates at the end of the experiment than sugar maples.
2Associate Professor and Research Technician, respectively.