Why leaves change color

Each fall, trees in and around Philadelphia change from green to a mix of red, orange, and yellow. After a few short weeks, the leaves fall to the ground, and the trees spend winter with bare branches. In spring, the cycle begins again. But what causes this impressive display?

In the fall, there are shorter days and colder temperatures. This makes trees work harder to circulate nutrients. In fact, trees go into a sort of hibernation because of the reduced sunlight!

In a process called “scarring,” trees stop producing chlorophyll and squeeze as much sugar as possible out of their leaves. This produces the lush yellows, oranges, and reds we hold dear.

Leaves dry out, become brittle, and eventually fall from the branch. The tree will remain dormant until the first signs of spring, when the days begin to lengthen and new buds start to bloom.

In the meantime, we rake the fallen leaves to keep our yards and public spaces clean. But did you know you can recycle leaves to keep them out of landfills?

How to recycle leaves

Leaves in brown bags

We’ve teamed up with the Streets Department to bring you the annual Leaf Collection and Recycling Program. Every Saturday through December 15, you can drop off bagged leaves from 9 a.m. to 3 p.m. at these 23 locations.

Make sure to:

  • Package leaves in biodegradable brown paper bags.
  • Never mix leaves with trash or other recyclable materials.

The leaves will be transported to the Fairmount Park Organic Recycling Center where the Parks & Rec team will turn them into compost.

Visit the Streets Department website for details on bagged leaf drop-off and mechanical leaf collection, as well as answers to frequently asked questions.