Who doesn’t love the autumn season? Red, oranges, and yellows, with the lower-setting sun, makes the landscape gorgeous.

Ever wonder why deciduous trees’ leaves change color?

As the cooler weather arrives, it signals to the tree that winter is coming. Trees essentially hibernate (go dormant) over winter, which helps them survive.

The weather signals the trees’ hormones to start abscission (to cut) – which severs the connection between the leaves and the stems.

The leaves are the workhorses of the tree through spring and summer.  They spread wide to capture sunlight and convert it to sugar through photosynthesis. They pull up water from the roots of the tree, to work with carbon dioxide and light from the atmosphere to create oxygen and sugar, which nourish the plant.

This is represented in the equation:

Carbon Dioxide + Water + Light = Sugar + Oxygen

If trees didn’t shed their leaves, they would lose water over winter through evaporation from the leaves.

So shedding the leaves conserves water and energy. Before the severing occurs, the tree draws in the moisture and chemicals from the leaves back into the stem to store in the roots.

That includes chlorophyll, the pigment that makes the leaf green. Chlorophyll is a chemical the tree breaks down for its nutrients to sustain itself over winter.

Once the chlorophyll departs, the leave true colors shine forth. Pigments called carotenoids and anthocyanins present at the cellular level give the leaf its color. Carotenoids (yellow and orange) are what gives carrots their orange color (beta-carotene) and are helpful in absorbing extra sunlight during photosynthesis. Anthocyanins (red) prevent the leaf from absorbing too much sunlight, particularly late in the season. Occasionally you may see a tree turn red in the top of its crown in early Fall, suggesting it’s trying to reduce some sunlight intake. These pigments give the leaves their stunning colors for a short period before it completely dries out and falls off the tree.

Then, these leaves decay and provide a blanket of mulch that helps protect the tree’s roots (and other ground plants) over winter. Leaves form a layer that helps the ground retain moisture, provide temperature insulation (protecting the roots from freezing), and emit nutrients and micro-organisms good for the soil profile.

The carbon cycle requires that living plants consume the essential nutrients magnesium, nitrogen, and potassium, among others on an annual basis. As those fallen leaves decompose, they are reduced to those basic elements and deposited back into the soil. They also invite healthy bacteria, microbes, and worms that work together to recycle the leaf litter and output needed chemicals.

Then as the tree becomes more active in the spring, it draws these nutrients through its network of roots. This is the process of recycling at its best and is an amazing function of the natural world.

We believe in taking care of good trees with precision and care. Sometimes that means removing a tree entirely if it’s diseased, at risk, or already dead but often it means working through a through-out management plan to help you preserve healthy trees on your property.

Serving eastern Baltimore County and western Harford County, we are your go-to expert arborists for tree services. Please contact us today to schedule your free tree assessment or ask any questions you may have.