All green plants, which includes trees, need sunlight to produce energy for survival. Some trees can satisfy their basic needs with less light than others. Sugar and red maples are two examples of such trees. They are both considered shade-tolerant; with sugar maple being more shade tolerant than red maple. This means a sugar maple can survive with less light for longer amounts of time than other species. This ability isn't simply making more with less; it's also about using less energy. For example, sugar maple can survive in the understory on just a few percent of full sun for years and can reach their maximum capacity at just 25% full sun. Shade tolerance is not the same as shade loving however. This is an important distinction since even though a given tree can survive for decades in the understory it doesn't mean it prefers to do so. The longer a tree has to endure living in a low light environment the less likely it is to respond with and if a gap in the canopy opens. To avoid this, make sure the forest management plan for a given property is written and followed to ensure regular thinning to produce adequate light.