Its January. Why haven't the leaves fallen off some of our local trees this year? Instead of bare branches, many trees are covered with dead brown leaves that stubbornly refused to fall.
Living in Canada we expect the Fall season to be filled with red, orange, and yellow leaves that inevitably fall off leaving the familiar bare branches of winter.
Why didn't the leaves fall off some trees this year? What does it mean?
The process that causes leaves to fall off is called abscission.
It also plays a part in leaves changing colour.
It's a natural part of the life cycle of many plants.
Plants produce organic compounds and hormones to better cope with their environment.
Take an average deciduous tree in the fall for example. The organic compounds and hormones the tree makes in response to its environment will break down the membranes of cells holding leaves to its branches.
The leaf falls off when the walls of the cells that hold a leaf to a branch break down and release the leaf.
It's important to note branches must be living to fully develop their abscission cells for the leaf dropping to happen.
If the process is stopped before it's complete the cell wall doesn't break down and the leaf remains attached. Even though it's dead
When the process of abscission is triggered, from cold or hot, shortened days, a drop in chlorophyll, etc., depends to some degree on the species of plant.
Obviously, the weather is a big factor. If warm days stretch into late autumn abscission might be slowed or delayed.
A sudden cold snap could then kill the leaf and connecting cells before the abscission process is completed.
The result is trees covered with brown dead leaves.
Not to worry. A tree's health isn't jeopardized by the dead brown leaves.
When it's time new growth will just push away the dead leaves.