In aspen, all the pigments that give rise to these glorious colors can be found in the leaf from spring all the way through fall (see here). As summer begins to end and overnight temperatures drop ...

Aspen is invariably the last tree to get its new leaves in spring, with them often not opening fully until early June in the Highlands, and it loses them in late September or early October ...

Quaking aspens store chlorophyll beneath their bark (particularly in younger trees), this is what gives the trunk a greenish cast. This helps them to continue to produce sugars, at least when the days ...