“What is the best mulch?”
I’ve been asked that many times, and it’s usually followed by further questions like:
“I have straw – will that work?”
“Can I use fall leaves?”
“What about black plastic?”
“We have horses – can I just use the stable bedding?”
“Would pine needles be good?”
The world of mulch is a complicated one, so I’m making it simple for you. Ready to discover the “best mulch?” Keep reading.
Organic vs. Inorganic Mulches
There are a lot of mulch options available, ranging from pebbles to tire rubber to dyed wood chips. If you go with something like pebbles or, worse yet, though big fake rubbery rings made to put around trees… you’re only getting weedblocking from your mulch and not much else.
One of the greatest benefits of mulch is its ability to feed the soil as it decomposes, making life better for the soil web and fungi in particular, which in turn makes your plants happier. Another benefit is the ability of mulch to hold in moisture yet still be permeable to the air. Plastic doesn’t allow that. Rock mulches are better than manufactured products like plastic, tire rubber shreds, etc., but they still don’t give you the benefit of adding organic matter to the soil.
Here’s my gut response on inorganic mulches: they’re only useful in very specific applications. If you’re interested in killing off a big area of grass, laying down black plastic or tarps works well. Long-term, though, you end up with sun-baked crackly bits of plastic everywhere, trashing your yard.
As for rocks – if you’ve ever had young children, you know that a patch of gravel manages to get redistributed here and there across your yard over time… and I have the pebble-filled sippy cup to prove it.
I will admit, if you’re going to set up a small nursery area or keep down weeds in a commercial-style row of grapes or blackberries, professional-grade woven weedblock plastic is nice to have. But in the garden or food forest? Naw. We need mulch to fill more functions than that.
So What Organic Mulch Works the Best?
This is one of those questions, like “how much space do I need for my garden?” The answer is… “depends.”
Just about any organic matter is better than nothing. Leaves, straw, pine needles – those are good. But some are better than others in certain instances.
As a quick example, pine mulches, either needles or back, are good for blueberries. Blueberries enjoy the acidity. In my opinion, it’s not quite as good for vegetable gardens. There I prefer to use leaves, straw or rough-ground mulch from a tree company.
Cedar mulch, though quite popular, breaks down too slowly to help with soil improvement, plus it repels some beneficial organisms. I avoid it unless it’s the only thing I can get, or if I’m working on a landscape job where the mulch needs to keep looking good long-term. A better option is pine nuggets, since they break down a little faster and look good for a long time.
Leaves make a good mulch, though some species tend to mat up and make it hard for the soil to breathe. Better to mix them in with other mulch, compost, straw, etc.
And speaking of straw, make sure you know where it comes from if you buy it. Straw is often contaminated with herbicides and pesticides that can cause long-term harm.
Stable bedding? Generally good, though I’d let it rot for quite a while before I use it – and I’d also top it off with another kind of mulch since horse manure in particular is often a big weed seed vector.
So what is the best mulch? Well, you may have another favorite, but my favorite is the afore-mentioned stuff from tree companies (like Paul Gautschi uses). I’ve caught crews who were clearing the power line easements in my neighborhood and had them drop mulch in my yard. They’re often glad to do so, since it saves them the cost of dumping it. Similarly, there are often city programs where all the “yard waste” gets tub ground into rough mulch. The problem here, though, is that you don’t know what went into the original mix. When I see the tree companies clearing the edges of my street, I can see what’s going into the mix. The neighborhood contains oaks, hickory, wild grapes, palms, sumacs, etc. All healthy wild trees. Unfortunately, when you get mulch from a municipality, you could be bringing in diseases, herbicides, pesticides, etc. What if someone threw in a pear tree that was infected with fireblight? Or a row of dead blackberries, infected with a virus? Or a tree filled with Aminopyralid herbicide? You could bring those problems to your garden, orchard or food forest. Not good at all.
Keep your eyes open for tree companies doing line-clearing work, or make a few phone calls. Though it tends to rob nitrogen when fresh, a great big pile of half-rotten mulch comprised of the leaves and trunks of a variety of wild species makes a great addition to your gardening projects.