Leaf senescence is a developmental program in which nutrients are recycled from leaves at the end of their lifespan. In annual plants, these recycled nutrients often support seed development. In deciduous trees, the nutrients can be stored in Autumn to support the growth of new tissues in the Spring. Thus leaf senescence is of great practical value to plants, and the cover photograph of a maple tree by Jordan Hall at Indiana University illustrates the aesthetic value of this process. To further understand this nutrient-recycling program at a molecular level, Bhalerao et al. (pp. 430-442) have studied, using microarrays, the changes in gene expression that occur as leaf senescence is initiated in poplar trees. Their work reveals a broad range of genes which, at the mRNA level, change in expression during leaf senescence (image from Rick Amasino).