Ramial chipped wood, also known as arborist wood chips – the stuff you can get for free from tree surgeons. It’s not just chipped up wood. It’s more of an 80% “green,” nitrogen-heavy content to 20% “brown,” actual woody content.
No, I’m not kidding. The best wood chips are barely woody.
There’s a whole variety of wood mulches out there that often get blanketed under the name “wood chips,” but what you’re looking for is the kind of wood chips that are made from the branches, leaves and pine needles of just about any kind of tree.
That’s right. The kind of tree doesn’t matter.
What does matter, however, is that the wood chips aren’t all the same size. You want there to be air pockets so that oxygen get make it to the soil beneath. Otherwise, your wood chips won’t compost very well and the roots of your plants are going to suffocate.
In case you didn’t know, plant roots need oxygen. That’s why compacted soil is not nearly as good as the soft, airy soil that develops when you’ve had your wood chips down for long enough.
Don’t till the wood chips into the soil. They’re a mulch, so they’re meant to be a covering, sitting on top of the soil and locking in moisture while they slowly break down and feed your plants below.
The bacteria that eat the wood chips and break it down use nitrogen to do so. If you rototill your wood chips into the soil, they’ll tie up the nitrogen in the soil until they’re able to break down enough. That means having to wait until the next year before you’ll be able to get anything to grow healthily.
Anyway, if all you can get is woody material without much organic matter, then you can simply add your own organic matter by growing a kind of green manure like red clover, Masanobu Fukuoka style.
As for the woody content, let’s take a look next at what to avoid.
What Wood Chips Are Not:
Bark Chips / Bark Nuggets
It’s fine to have bark in your wood chips, but avoid going purely for bark chips.
Bark chips take way too long to break down, so they’re not going to be feeding your plants very effectively. They’ll break down eventually, which is why it’s fine to have bark mixed in with your wood chips, but they don’t provide extra nutrients or anything so they’re just plain slower.
Sawdust has two main problems.
The first, is that they sit together too densely and block airflow. If oxygen isn’t getting to your plants’ roots, it doesn’t matter how much they’re being fed by the sawdust breaking down: they’re going to die off. Nutrients simply cannot replace oxygen.
The second problem with sawdust is that it gets mixed into your soil way too easily. That means you’ll end up tying up the nitrogen in you soil without even realizing it.
Each time it rains, a little more sawdust will mix into the soil until you’ve got a complete mess. The only way to fix that would be to wait until the year after when the sawdust has broken down enough.
Oh, there is actually one more downside to sawdust: it’ll just blow away if there’s ever a strong wind. Yeah, that alone pretty much defeats the point of them.
Okay, they’re not too bad, but they do suffer from the whole compaction problem.
Simply put, they get squashed together way too easily. You’d have to make sure they keep “fluffed up” enough, which would just be a real pain. Also, if you did that, there’s always the chance that they’ll blow away on a windy day.
Dyed Wood Chips
If they’re a natural dye that is non-toxic to plants, then they’ll be fine to use, but just be wary that many kinds of dyed wood chips break down slower than your usual wood chips.
If you want colored wood chips, choose ones that are sourced from a kind of tree whose wood is already the color you want.
Really Big Wood Chips
Again, they’ll break down too slowly.
They’re also harder to walk on, which makes it not quite as nice to wander around your food forest. With good wood chips you’ll be able to walk on them barefoot if you wanted to.
Also, the problem with wood chips that are too big is that they’re physically harsh on plants too. They’re too heavy, and can damage your plants too easily if you’re not careful enough.
Go with some nice small to medium sized wood chips. You’ll thank me later.