Please note: This article was originally published on 10/16/2020 and was republished on 11/11/2021.
Of all of our seasons, I’ve heard more people proclaim their love of fall than any of the others. It marks an end to the uncomfortable heat of summer and traditionally represents a time when we reap the gifts of the harvest and prepare for winter. And for several weeks, our trees also gift us with a wonderful display of color. Everyone has a favorite - the brilliant orange of our native sugar maples, the rich yellow of the non-native maidenhair tree (Ginkgo), the reds, purples, and browns of oaks.
Fall is a time marked by traditions. And when those beautiful leaves begin to fall, we have another long-standing tradition. We clean them up, put them out at the curb, and praise ourselves for the hard work and tidy-looking yard. In doing so, we avoid being “that neighbor” who doesn’t clean up their leaves, which, with a few windy days, find their way back into everyone else’s yards. By cleaning them up, we also avoid a build-up of debris, moisture, insects, and pests in the outside corners of our homes, fences, yards, etc. There are plenty of reasons why we don’t want to just leave the leaves wherever they fall.
But in cleaning up all of those leaves, we are also inadvertently disrupting a natural process and contributing to a host of very common problems in our landscapes. As mentioned above, fall is the season of harvest. As it turns out, this holds true for our trees as well. Even though they have been manufacturing food for themselves throughout the year by way of photosynthesis, in the fall, the leaves that fall to the ground begin a slow process of decomposition. Eventually, if left in place, they will become organic matter that improves soil structure and provides a wealth of needed nutrition to the root systems of trees. I like to think of this as the tree’s gift of a fall harvest to itself.
One of the most widespread problems that this “clean up” contributes to is the chlorosis that we see in common landscape trees like red maples, pin oaks, and river birches. You don’t have to look very hard to find a red maple or pin oak in an undisturbed wooded area in central Ohio. But you’d be hard pressed to find one in such a natural environment that is struggling with chlorosis. This is because the soil in these areas contains more organic matter, and in turn contains more nutrients and also a lower pH level, which allows the key nutrients associated with chlorosis to be properly absorbed by the tree roots. When we look at it this way, chlorosis is a man-made problem, typically only found in our urban landscapes where we create conditions that aren’t always best for our trees. Some other issues that leaf cleanup can contribute to are general nutrient deficiencies and also surface roots, where roots must grow closer to the surface in an attempt to get more oxygen due to the dense clay-heavy soil that is lacking an adequate amount of organic matter.
So what’s the solution? How do we help provide suitable conditions for our trees without abandoning leaf cleanup and annoying the neighbors? There are a few things we can consider:
#1
Leaf mulching in the lawn
Though this may have limited benefit to a tree’s roots due to the aggressive nature of turf and its ability to successfully compete for water and nutrients, mowing over the leaves instead of raking them will help to return some leaf litter to the yard and possibly increase the amount of organic matter in the soil.
#2
Leave the leaves!
Wherever possible, try to leave the leaves that fall and let them break down over the winter months. Perennial beds located around trees are a great place for this, where you should be considering leaving the dead perennial tops until spring for the same reason. In many urban landscapes, there is unfortunately a limited number of areas in the yard where this is an option, since the expectation is to have neatly mulched beds and crisp bed edges. Whether that approach is right or wrong is largely a matter of opinion, but it definitely does not favor the overall health of our trees.
#3
Reduce the size of the lawn
We recommend that turfgrass is removed from within the drip line of the tree. The leaves that fall each year will then be able to stay within this area, decompose, and provide vital nutrients back to the tree.
In writing this article, I considered titling it “Tear Out That Turf!” instead of “Leave Those Leaves!”. Turf grass is an amazing groundcover that gives us outdoor spaces that we can enjoy in a number of ways. It’s so hardy, we can literally trim it once a week and drive vehicles over it without killing it. Try doing that with just about any other type of plant, and the results won’t be pretty. But along with being hardy, it requires a significant amount of resources. And perhaps more relevant to this article, we can’t leave it covered with leaves and expect it to survive. Trees and grass represent parts of our natural world that are typically separate from one another. Most of the world’s trees grow in communities that we call forests. Grasses are sun-loving plants naturally found in prairies, fields, and meadows where they don’t get buried in leaf litter once a year. Generally speaking, the one place in the world where they are found coexisting is in our yards, artificially so, and with a lot of help from us. One of the best things you can do for your trees is to increase the space around them and under them that is void of turfgrass. This will reduce the amount of competition for water and nutrients, and also allow for a larger area of soil that you can improve with leaf litter or other soil amendments. It’s important to exercise caution if you choose to remove the turf around your trees so as not to damage the roots that may be present immediately underneath. If you decide to go this route but want some help, we offer a service called root-zone invigoration, which uses high-pressured air to remove turf and cultivate the soil without any mechanical damage to the delicate root system. This is often done for a specific reason related to a tree’s health, but it is also one of the best ways to increase the turf-free zone around a tree.
IN CLOSING…
I’m confident that no lawn care company ever has or ever would write an article about leaving leaves and getting rid of turfgrass, but as an arborist, I'm probably biased towards the trees. Many of the tree-related issues that occur in our urban landscapes are a result of the conditions we create. Allowing for a more natural approach while stilling doing our part to maintain the property should be something we all consider. As always, give us a call or email us with any questions. Just not questions about your lawn, we’ll probably tell you to tear out that turf!
Walter Reins | Regional Manager, Russell Tree Experts
Walter has been an ISA Certified Arborist since 2003. He graduated from Montgomery College in Maryland with a degree in Landscape Horticulture, and has called Columbus, OH his home for nearly 20 years. Walter appreciates trees for their majesty and the critical role they play in our world.