Leave the Leaves?

To leave or not to leave, that is the question. Over the past several years, this query has become a hot topic among gardeners. It used to be common practice to diligently rake every single leaf off the lawn in the fall. These leaves would be gathered into a pile, placed into bags, and hauled off to the landfill. If you were lucky as a kid, you’d get a chance to jump into the pile of leaves before they were bagged. We’d leap and dance, throwing leaves into the air and scattering them across the lawn once more (much to the chagrin of those who had raked them). It was the highlight of the season! But now, some experts are saying to leave the leaves to benefit the wildlife, the soil, and your garden. Conflicting opinions abound, so what’s a gardener to do?

In 2014, the National Wildlife Federation published an article touting the importance of leaving the leaves for wildlife. The publication pointed out that a leaf layer is its own ecosystem, providing a primary habitat for many species, including chipmunks, wood frogs, box turtles, toads, salamanders, earthworms, and thousands of insect species. Leaves are also an overwintering location for many butterfly and moth species, whether they overwinter as eggs, pupae, or adults. Ninety-four percent of moths rely on the leaf layer to complete their lifecycle. By raking up and hauling away our leaves, we are getting rid of critical habitats for beneficial insects and pollinators. These insects are a vital food source for many bird species that forage in leaf layers. Approximately 96 percent of our backyard birds rely on those butterfly and moth caterpillars to feed their young during nesting season. And some bird and bat species even nest in the leaf layer itself. So, it stands to reason that if we get rid of the leaves, we will have fewer insects and birds to grace our landscape, pollinate our gardens, and enjoy.

Because I’m a strong supporter of wildlife, these points alone were enough to convince me that leaving the leaves was a good idea. But wait, there’s more! Upon further reading, I’ve discovered some added benefits to keeping all of those leaves, especially for the garden.

When fallen leaves decompose, they return valuable nutrients to the soil. They also provide food for earthworms and beneficial microbes and can lighten heavy soils and help sandy soils retain moisture, improving soil quality. Besides improving the soil, leaves can be used as a natural mulch on garden beds and around shrubs and perennials. They can also provide insulation for tender plants during the cold winter months. If using leaves as mulch, spread no more than a 3-4 inch thick layer and do not pile them up against stems and trunks. Also, in the spring, you may want to brush them aside to allow new shoots to emerge unhindered. Shredding the leaves is always best in the garden, as it helps prevent them from packing together, limiting light, water, and air circulation. Shredding also reduces volume and allows the microbes to break them down faster, making the nutrients available to your plants sooner.

Additionally, leaves are an excellent carbon source for compost piles. If not using them on your garden beds directly, consider saving dry leaves and using them in the summer months when carbon sources for the compost bin are not as readily available. If you still prefer to rake your leaves into a pile but don’t have the energy to shred and distribute them in the garden, no worries! Leave the leaves in a pile and walk away. In 1-3 years, you will have leaf mold, a marvelous soil amendment that lightens soil and retains moisture just as well as peat moss-and is a renewable resource!

Of course, there are some caveats to all of this foliar bliss. For example, it is not recommended to allow leaves to form thick mats on lawns, as they can block sunlight and trap excess moisture, killing the grass underneath. To avoid this scenario, mulch the leaves, creating smaller pieces that will break down quickly. Alternatively, you can get rid of your lawn altogether and grow more native plants! Also, some tree species’ produce a chemical called juglone, which can inhibit growth in other plants, a phenomenon called allelopathy. Aren’t plants fascinating! You want to avoid using the leaves of these species in your gardens. The most common allelopathic species are walnut (primarily black walnut), eucalyptus, and camphor.

In the fall, when the leaves start to drop in abundance and swirl around in the breeze, I run outside yelling, “Hallelujah, it’s raining mulch!” Then I grab my rake and begin to harvest the season’s most bountiful crop: leaves. Yup, this gardener has decided to leave the leaves.

Sources: National Wildlife Federation, Put Fall Leaves to Work, & Plants That Inhibit Other Plants