Can You Use Whole Leaves as a Mulch?

You might want to use whole leaf mulch between garden beds, but probably not in the beds themselves. Photo: sergabblog.wordpress.com

Question: I notice that in your blog, you often recommend using a mulch of shredded leaves. I have plenty of dead leaves, but they’re not shredded. Would they still make good mulch?

Isabelle Allard

Answer: Yes and no.

Small leaves (those of birches, willows, elms, etc.) make a very good mulch even without shredding, as they form a fairly light and fluffy layer that allows plenty of air circulation, just what you’d want in a mulch.

The problem is mainly with large leaves (like those of maples, oaks, planes, etc.). These leaves sometimes seem settle flat one on top of the other, even interlocking. This creates a barrier that makes it difficult for garden plants to sprout through in spring. Also, this same dense accumulation also reduces air and water circulation, notably reducing the air circulation to the roots of plants: never a good thing. It also reduces the efficiency of soil microbes, the ones that enrich the soil by decomposing fallen leaves. 

A whole leaf mulch can sometimes be the opposite of a good mulch: heavy and dense rather than light and airy.

Also, oak leaves, especially, contain a lot of tannins, phenolic substances which can seriously reduce decomposition. If you chop them into tiny pieces, though, the tannins are quickly leached out.

Soooo, if you want to use whole leaves as mulch, you can, but if you see your mulch is packing down in places, do break it up with a hoe or rake.

So Easy to Shred

On the other hand, it seems to me that shredding leaves before using them as mulch would not be that complicated. You can chop them up simply by running over them with a lawn mower or put them in a trash can and chop them with a string trimmer.

It’s up to you, but I think you’ll have better results if you shred the leaves before using them as mulch … or even putting them in the compost.