5 hard truths the “leave the leaves” advocates won’t tell you

As a self-proclaimed “lazy gardener,” I was initially excited to learn that leaving the autumn leaves on the ground could benefit the ecosystem. Proponents of this method tell you not to rake up your tree droppings in the fall, but to leave them alone until spring. This helps mimic nature’s cycles (no one is taking a rake to natural forests) and gives pollinators a space to hibernate for the winter. It also creates a natural mulch, enriches the soil, and helps suppress weeds.

All this is true, but it doesn’t tell the whole story. Here are five inconvenient truths based on my experience with “leaving the leaves.”

1.     Agh! Too much nitrogen!

Decaying leaf matter is like nature’s slow-release fertilizer. Specifically, it adds more nitrogen to the soil, which plants need to grow.

The problem is not all plants are crazy about nitrogen. My lavender shrubs, for instance, don’t need a lot of nitrogen. In fact, too much nitrogen causes the plant to produce fewer flowers. Obviously not the goal, especially when making lavender sachets.

The same is true with a lot of California native and drought tolerant plants. They’re used to growing in poor soil. When the soil suddenly gets a lot of nutrients, they don’t know what to do.

2.     Agh! Too much water!

In a similar way, drought tolerant plants are used to going long stretches without water. Leaving a layer of leaf mulch helps retain water in the soil. While this can be great for heavy drinkers (looking at you, hellebore), it can harm drought-tolerant plants.

Again, lavender was my canary in the coal mine. The leaves on my lavender shrubs started turning yellow, even though the surface of the leaf layer was dry. A quick dig underneath, however, revealed consistent moisture, which was causing root rot in my lavender.

3.     Disease and despair

Ok, so drought tolerant plants don’t need extra nitrogen or extra water. But surely plants that need both could benefit from an extra leaf layer, right?

Maybe. But your risk for disease increases, especially for sensitive plants like roses.

Black spot is a common fungal disease in roses. The leaves get (can you guess?) black spots and drop off early. This weakens the plant. One source of the fungus is decaying leaf matter, which is why rose experts will tell you to clear the area around your roses after pruning.

So even though I thought I was helping my roses by giving them a leaf mulch, it wasn’t beneficial for their overall health.

Some roses are more resistant to black spot than others (I actually noticed it on only one of my rose bushes). But keeping the area clear of leaves gives them all a fighting chance.

4.     A rug for your slugs

More moisture and more decaying matter mean a great habitat for slugs. This is probably the number one pest I have.

5.     Your neighbors will totally judge you

This last point isn’t a serious problem, but the overall presentation of a leaf-filled yard is something to consider. I want my space to look like a flower farmer lives here. Maybe a tidier front yard will inspire more admiration, or at least cause people to leave less dog waste behind (or maybe that’s just Oakland…).

What to do with all those leaves?

There are still benefits to leaving the leaves. The sparrows that hop around my yard and dig for insects are definitely fans of leaving the leaves alone. There are two spaces in my backyard with leaf mulch, and it really does help the plants.

What I may do in the future is gather the leaves into specific spaces where I want the richer soil, away from my lavender and roses. Or perhaps some will go directly into my compost to create next year’s soil.

My neighbor’s tree is the biggest contributor of leaves in the yard. Leaving them as a natural mulch could have been ideal for different plants instead of the drought tolerant or California native plants we have currently. What could have been a natural asset instead becomes a threat (or at least an asset that needs to be moved each autumn).

Permaculture considers these connections, the links between different plants and systems. Maybe someone planning the yard with a permaculture perspective would have chosen different plants. It may have made more sense, but I like our lavender, the manzanita, and the California redbud.

I guess I’ll just keep raking the leaves.

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