Each year in autumn, many deciduous trees change colour and drop their leaves. However,

I’ve noticed some trees, such as oaks and my grandma’s Japanese maple, hang on to their brown, dead leaves until spring when the new leaves essentially push them out... and these brown leaves are stuck on well! Why is this? Is there a particular reason?

Kate Hodgson, Giralang, ACT

PHIL DUDMAN SAYS While they have come up with a name for this strange phenomenon (marcescence), scientists haven’t figured out why it occurs. Some speculate that it has something to do with nutrient cycling. If the leaves are held on the tree until spring when a fresh canopy of leaves appears then, rather than blow away, the dead leaves are more likely to remain on-site where they break down and return nutrients to the soil that surrounds the tree’s root zone. Others suggest that the leaves remain on the branches in order to obscure buds from grazing animals.