How to Save Leaves for Beneficial Insects
The Wrong Way, Leaves will Attract Pests and Weeds
Leaves sitting along the walls will provide shelter to rodents like mice. If the leaves are not swept off paved areas like sidewalks, parking spaces or even on gravel, they will slowly decompose into a humus soil rich in nutrients. Weeds could then grow in cracks of the driveway, between interlock pavers or among the gravel. In the past, RoundUp was an option for such weeds. However, more and more jurisdictions are banning such herbicides used for aesthetic purposes due to health concerns. Vinegar is sometimes used as a DIY weed killer. However, as vinegar is an acid, it will dissolve minerals in the paving materials and this will accelerate the degradation of sidewalks and driveways. So don’t let the leaves stay on these surfaces. Sweep or use the blower to get the leaves off of these surfaces.
Seeds are Even Worse
Don’t miss the seeds - they are even worse. Seeds are densely packed with nutrients. Critters will love eating them! If they are not eaten, they will decompose into an even richer organic soil. Over time, the seed crops of the following years might have enough soil to successfully germinate. It just goes downhill from there.
Done The Right Way, Leaves will Attract Beneficial Insects and Suppress Weeds
The Right Locations are Near Pollinator Plants
If you are saving leaves, keep them close to plants that attract pollinators. Beneficial insects, such as lacewings, ladybugs and hover flies, make use of the same plants and overwinter in them. Pollen and nectar from these plants provide valuable proteins and carbohydrates. When prey such as aphids is in short supply, pollinator plants can be an especially important source of nutrition.
Once again, in the wrong place, say, next to the living room or bedrooms, pest insects like carpet beetles may thrive and migrate indoors.
The Correct Thickness
Leaves piled up high enough could start to compost. This is not what we want nearby living plants. Rather, the thickness we are looking for is to provide insulation for the overwintering insects.
What about the Wind?
One leaf thick and the wind might simply blow the leaves away. At about two inches, the layer could maintain even moisture and regulate temperature. At this point, leaves tend to start sticking together. Maybe it is the mycelium spreading from fungi - I can’t say for sure - but whatever it is, it seems to hold things down fairly well in the wind. You could always water it if high winds are in the forecast when the leaves are still fresh and loosely packed. Compacting to two inches is a good goal. At this thickness, it will also help suppress weeds the following year.
Seeds and the Benefit of Sow Bugs
The seeds should go in the ground cover of leaves. The germination rate typically is not that high when mixed in leaves. Seeds will decompose into great fertilizer. You may notice pill bugs - variously known as sowbugs, woodlouse, potato bugs, etc - the following spring. They are decomposers so they will process the tree litter for you. No composting needed!
Moles and Pollinators
When dealing with pest critters at clients’ properties, I often observe native pollinators coming in and out of burrows. Whether it is the burrow of rats, mice, and even skunk, pollinators seem to appreciate the burrows. These pollinators often nest in soil but we don’t leave them much bare soil when we cover every square inch with greenery. Perhaps we could tolerate moles better than other disease-carrying pests. Unless you have young fruit trees, you might want to help protect some moles with this layer of leaves, away from the walls of course. The burrows moles create could give pollinators better access to the dirt they need. Moles do look strange with outsized hands, but a bit of compassion for this blind creature could help us save pollinators.
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This blog covers a variety of topics related to pests, which includes weeds, insects, birds and other wildlife - indoors and outdoors. We also cover the pests of pests, such as beneficial insects!
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