As trees form, the size and shape of its stem and crown, will be impacted by living in a low light environment such as the forest's understory. So-called suppressed trees are able to capture just enough sun to survive. Sugar maples growing in the understory tend to leaf out earlier than the trees in the upper canopy. When measured, it has been shown that these understory trees will produce as much as 80% of their entire annual food production in that short period before the canopy closes in and light becomes more limited. Perhaps the most visible impact of a tree being suppressed for a long period of time is a characteristic "flat topped" crown. This results from the tree growing attempting to get sun from the sizes rather than from above. Trees whose branching has been impacted this way will have a harder time responding if a gap in the canopy were to open up. These poor formed individuals will generally not mature into large, tappable trees.