This summer in Nashville has been a hot one! Our work crews are certainly ready for a break from the heat, as are the trees. This year, I have seen some trees bypassing their fall colors, turning brown quickly, and falling from the tree soon thereafter. Heat and drought can certainly impact fall color, but most healthy trees will fare the heat and drought well, while others will not be as fortunate.

Fall is the time of year when we see new colors (that have been masked all year by green chlorophyll pigment) appear. As these new pigments expose themselves, vibrant reds, yellows, oranges, and purples may appear (Figure 1). Following this color change, trees will soon abscise (drop) their leaves—allowing them to float elegantly down to the ground. These fallen leaves then provide wonderful ecosystem services (even on a small scale), primarily benefiting the soil, but also the trees and surrounding plants. Yet, as I drive through town, I commonly see homeowners out in their yards raking up and removing these leaves, stuffing them in paper or plastic sacks, and stacking them out by the road, to be hauled off to a landfill. This year, I hope to encourage you to keep these leaves in place.

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Figure 1. Fall colors shining through.

Where to see Fall Leaves Tennessee – Best Views

For the best opportunities to see fall colors, I would encourage you to drive east, toward the TN/NC state line. Here, the colors seem to pop in ways that we do not commonly see in the highly-urbanized city limits of Nashville. If you are able, get out of the car and hike a local trail (if even for a short hike). You never know just what joys our wonderful forests may be waiting to show you!


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Figure 2. Not a lot of grass in a forest system.

Grass Growth under Trees

I commonly inform homeowners that grass and trees don’t play well together. While estimating, I will likely ask, “if you were to walk into a local forested ecosystem, how much grass would you see growing beneath the trees?”—the answer is none (Figure 2). Instead, you are much more likely find a thick (~ 6” layer) of fallen leaf litter, being slowly broken down by the elements, soil-dwelling microorganisms, insects, and Fungi; all greatly benefiting the entire system—especially the trees. Organic decomposition of this leaf litter also aids soil aeration, builds up soil structure, changes soil texture, and slowly releases nutrients that have been built (and stored) all summer back to the trees. In addition to this, leaf litter helps to produce a vibrant and healthy below-ground biotic community that is commonly absent in urban settings.


Eco-friendly Ideas for Leaves in Your Yard

So, what should you do with those leaves? I would propose two options for your leaves this year. 1.) Simply cut (i.e., mulch) over the leaves in your yard with your mower over the course of two-or-three cuttings, allowing these smaller (mulched) leaves to more rapidly decompose and be added back to the soil just beneath your trees. Not only will this help to get rid of the leaves, these smaller cut pieces have less of a chance to kill large patches of grass if that is an area of concern for you. 2.) If you absolutely do not want leaves left behind in the yard, go ahead and remove them. Rake and bag them, but instead of disposing of them, I would recommend you start (or build up) your existing compost pile. This starter material is completely free and will require little maintenance. Of course, compost piles will need a combination of both brown parts (carbon) and green parts (nitrogen) in order to actively decompose. (More on compost piles in a later blog post).

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Figure 3. Differences in root growth (by soil type).

Tree Roots and Leaf Mulching Improve Soil

In arboriculture, healthy roots are the name of the game. The healthier your soils, greater root growth will be expected (Figure 3). Building up your soils, by returning the leaf litter back to the system can help aid in this root growth. In essence, mulching your leaves becomes a great way to fertilize your trees in the best possible way—through the slow breakdown of these organic components which then become more usable to the trees and surrounding plants.

Happy Fall from Community Tree Preservation!