Piedmont Gardener

Southern Red Oak (Quercus falcata) beginning its autumn transition

If you haven’t read Douglas Tallamy’s book, The Nature of Oaks, I highly recommend that you put it on your to-read list. This book is shorter than his others, because he focuses on one tree genus – oaks – instead of entire forest and field ecosystems. By so doing, he is more successful at vividly painting a picture of the complex web of life supported by these long-lived forest giants.

A White Oak’s Tale

To tell the story of oaks, Tallamy centers his tale around one oak tree, likely planted by a blue jay as an acorn several decades earlier. Every chapter chronicles one month in the life of the tree. The entire book is worth reading, but with autumn’s recent arrival, I want to focus today on leaves – the ones discarded by deciduous trees about this time every year, including most oak species. When left alone as Nature designed them to be, these fallen leaves form what Tallamy rightly describes as “priceless litter.”

Magic Beneath the Trees

March is the chapter in which Tallamy tells readers about the magic of fallen oak leaves (He spent his October and November chapters on acorns). As an entomologist, Tallamy is better acquainted than most with the millions of insects and other creatures – most quite tiny – that spend their lives in leaf litter. Soil ecologists call these creatures detritivores. They consume dead plant parts or the bacteria and fungi that help break down plant cellulose in fallen leaves. Dozens of species of moth caterpillars are part of this mix; they eat dead leaves instead of green ones. Of course, these creatures are also eaten by detritivore predators, which number in the hundreds of species. These leaf-litter dwellers provide a critical function by recycling nutrients in dead leaves back into forms plants can absorb via their roots.

All fallen leaves contribute to this mostly unseen web of decomposers critical to nutrient recycling that fuels all life. But oaks, Tallamy tells us, create leaf litter that sustains decomposer populations better than all other tree species. The 700,000 leaves that fall from a mature oak tree decay more slowly than those of most other species, providing ideal litter for up to three years. Decomposers need consistent conditions to survive. Bare soil cannot sustain them; it lacks the nutrients and even moisture levels they need. Slowly decaying oak leaves piled beneath their mother trees provide ideal conditions for the occupants of this intricate food web to perform their magic.

Water for Tomorrow

Tallamy notes that a thick carpet of leaf litter also acts like a sponge during rains. Instead of running off bare ground into storm drains, raindrops soak into leaf litter, which is especially beneficial during heavy rains. Tallamy notes that almost all of a 2-inch downpour – more than 54,000 gallons/acre – is absorbed by leaf litter in an oak forest. Slowly, that water seeps down into the water table, where we and the plants can use it in the future.

While that captured downpour is seeping through the litter, it is purified. Excessive nutrients (for example, runoff from overfertilized lawns) and pollutants are captured by the litter, allowing clean water to filter down to the water table. Instead of flooded streams full of pollutants and eroded soil, clean water slowly seeps downward, replenishing streams downhill gradually, ensuring that flora and fauna relying on those aquatic environments are not disrupted.

More Oaks for More Magic

Tallamy’s message in this book is straightforward. He asks that we all plant oaks appropriate to our region now. It is true that oaks planted now will not mature in our lifetimes, but that is not a reason not to plant them. Gardeners know. We plant for our grandchildren. We plant to enrich habitats for native wildlife. We plant to heal our deeply wounded planet. We plant for the magic created by our vision and effort – not just oaks, of course, but yes, definitely oaks too.

Northern Red Oak Acorns

This fall – the ideal season for planting trees and shrubs in the Southeastern Piedmont – please do plant some oaks and other native trees and shrubs. But there is something else you can do that will help. Stop destroying the leaves your plants return to Mother Earth this season. Leave those leaves in place wherever possible. If you must move them, move them gently, to minimize damage to the tiny creatures using those leaves.

Leave Your Leaves

In my yard, wherever practical, I simply rake fallen leaves around their donor trees. In the few areas where I’m still maintaining a “lawn,” I gently rake the leaves around nearby trees. I’ve created a wonderful, increasingly spongy leaf litter bed in my front yard over the last two years by raking about half of the fallen leaves from a massive southern red oak around two ornamental trees. Their leaves also contribute to the litter, but it is definitely those slowly decomposing oak leaves that have created a magically moist, fertile bed into which I’m now adding native ferns and spring ephemeral wildflowers.

Store-bought mulches cannot substitute for leaf litter mulch. They don’t contain the nutrients the millions of detritivores need to survive. It is past time for us to discard old landscaping practices that promote military neatness. Leaves are not the enemy. They are our salvation.

My local Audubon chapter (New Hope Audubon) is currently conducting a wonderful program in collaboration with Triangle Community Foundation and Keep Durham Beautiful, Inc. to promote preserving our leaf litter in place. It’s called Leave Your Leaves. The campaign provides brochures, posters, and yard signs promoting this program. You can read all about it here.

Even if your aren’t a Durham, NC resident, please consider visiting the Pledge To Leave Your Leaves link and signing the pledge. The grant that provided funding for this effort is tracking the number of folks who sign the pledge as a measure of the campaign’s success. If this campaign is successful, it will be easier to win future grants for additional environmental education programs.

Learn More About Healthy Yard Alternatives

Next Thursday, October 21, one of my area’s local conservation organizations (Chatham Conservation Partnership) is holding its quarterly meeting. It will feature several speakers presenting information on healthy yard alternatives. The good news for all my readers is that this meeting will be virtual. If you have the time and a decent internet connection, you are welcome to register and attend the meeting at no cost to you. For details on the meeting and how to register, go here.

A big step toward bringing the magic of a healthy ecosystem to your landscape is leaving fallen leaves in place to shelter the millions of tiny creatures who need them. They, in turn, feed plants with the nutrients they recycle. And the plants feed us all.

Bring back the magic. Leave your leaves.