To Mulch or Not to Mulch


I was out working in the garden the other day (what else is new?), crawling under some rhododendrons, thankful it’s not yet spider web season, and gently scraping my hand rake along the top layer of leaves, getting the bed ready for the spring tradition of spreading a nice, 3-inch thick layer of mulch.

Mulching is defined as “material spread around or over a plant to enrich or insulate the soil.” It’s also good for suppressing weeds, retaining moisture and preventing erosion. Different textures and colors of mulch, such as wood chips and beauty bark, can be seen applied in both parking lots and residential gardens. In my family it is customary to apply a fine, dark mulch.

Spreading mulch had always made sense to me, if only to make the yard look nice and orderly. But there I was, after a few hours of getting the gardens prepared for the traditional spread, covered in dirt, getting smacked by rhody leaves, when I looked down at the soil my rake had exposed and noticed there were no weeds, the dirt was moist, and threads of fungus had already been hard at work breaking down the debris.

This little observation of mine got me thinking: Why am I redoing what the garden has already done for itself?

I’m certainly not the first person to have the radical revelation that we should mulch our gardens with leaves. Or, at the very least, not bother to rake them out.

There’s been a movement in recent years to educate gardeners and homeowners about the benefits of “leaving the leaves” to create landscapes that are climate-resilient and to preserve biodiversity.

Allowing the fallen layer of leaves to remain in place during the autumn and winter helps to prevent erosion and acts as protection for the tender crowns of perennials and hibernating insects. As the weather warms up, the leaves regulate soil temperature, preserve moisture during droughts, and feed the soil organisms that recycle the nutrient in the leaves back to the plants.

Nutrient cycling is a particularly compelling component for why we want to allow leaves to remain in the flower beds year round. Leaves contain basic nutrients like nitrogen, phosphorus and potassium, as well as trace minerals that the plants have taken up through their roots from the depths of the subsoil.

Once decomposed, the old foliage not only ends up feeding the plants again, but also contributes to the structure and health of the entire soil ecosystem. Forests are a great example of how effective the system is.

I’ll admit that decomposing leaves are not a particularly appealing aesthetic but finding other ways to utilize the organic material elsewhere within the landscape should be considered before sending it off in a yard waste bin. One way to do this is to build a compost pile. Leaves take about one year to break down on their own, or three to six months with regular turning.

I’m very much on board with the ecological benefits that come with leaving the leaves. Nevertheless, what was particularly appealing about my initial observation while raking the garden bed is that the work had already been done for me. The mulching, that is. And as someone who is interested in developing a more laissez faire approach to flower bed maintenance, leaves as mulch is just the tip of the iceberg when it comes to solutions for cultivating a low-input landscape.

Taking cues from natural processes has also inspired new ways to approach how we plant and maintain our gardens. Landscape designers who specialize in creating naturalistic planting schemes have learned to organize beds in such a way that yearly input ends up being minimal because the plant communities they’ve created do the work for them.

Landscape designer Roy Diblik, in his book “The Know Maintenance Perennial Garden,” talks about the nature of perennials, stating “Many perennials do best in lean soils relatively low in organic matter, and what organic matter there is develops in the soil from all the plant parts that fall to the ground each year.” Some plants also prefer drier conditions, so regular applications of mulch coupled with regular irrigation can end up inhibiting growth and rotting the crown of the plant.

He also points out how in America we tend to space perennials too far from one another, fearing overcrowding, when in reality plants prefer to be close because that is how they tend to grow naturally. The dense foliage ends up mulching the soil, preventing weeds and retaining moisture the same as an application of a wood mulch. And this is a wonderful piece of information for us gardeners to have because what once could be characterized as a chronic plant addiction can now be justified as the cultivation of living mulch. “I don’t have a problem — the exposed soil has a problem!”

For the sake of continuity, I removed the rest of the leaves from the garden bed and hauled them to the compost. As I collected the pitch fork and wheelbarrow to begin chipping away at the pile of delivered, commercial mulch, I was ruminating on the guilt I felt for having disturbed the precious and fragile ecological process taking place right in my garden. But as I began to load up forks of the super fine, soft, fluffy shredded mulch, I had a moment of reprieve, thinking maybe this mulch won’t be so bad. The garden beds will look fresh and the plants get all the same benefits of decomposing organic material. And then I saw the little bits and pieces of plastic in the fresh mulch.

I’m leaving my leaves next year.