Thinking about wood chip mulching in your vegetable garden? What are wood chip mulch pros and cons? Here are 5 things you should know BEFORE you start spreading those wood chips.
I’m not much into writing about controversial topics. Honestly, anytime I’ve ever even touched on controversial topics the response usually unnerves me. I’m robbed of peace and distracted to the point where I’m not doing my home duties properly. So I steer clear. Easy enough?
You’d think so. But apparently, a topic so innocuous as mulch is a hot-button topic in the gardening community. Who knew?
Well, I do now, that’s for sure! And I can’t help but press it again.
Despite many glowing (often short-term) trial reports after mulching annual vegetables in wood mulch, many are having experiences quite the opposite. Even though they follow all the rules for wood chip mulching.
And now, while studying up on permaculture, I’ve learned a new tidbit of information. It added one more reason to the case I’ve built about why using free wood chip mulch in an annual garden might not be a good idea. (It’s point #5 and it’s pretty important!)
Quick Tip: When you start a new experiment on the homestead how are you going to know if you really got the results you think? When you keep good records with the SmartSteader homestead management app you can learn which systems truly worked and which ones didn’t. The answer lies in the production and cost-effectiveness. With SmartSteader you can record gardening expenses and yields so you can know if you are really growing more if you are really having to do less work if you are really saving money!
5 Things You Should Know About Wood Chip Mulch
Wood Chip Mulch Can Mess With Your Garden Acidity
Many people who are flagging down tree services don’t know what types of trees are chipped up. And some trees are anything but pH neutral. You need to be aware that some mulches can have an adverse effect on soil acidity. See also: “Do Conifers Make Soil More Acid?
Long-Term Use Of Wood Chip Mulch May Increase The Fungal Dominance In Your Soil Food Web
What’s the big deal about that? Annual vegetables prefer and do best in bacterially dominated soil. Your vegetables might do really well the first few years, but once that fungal dominance is established, you may notice a decline. This is the reason I started to rethink mulch gardening in the first place.
Wood Chip Mulch Requires That You Use a LOT of Composted Manure To Balance The C:N Ratio
To offset the high carbon to nitrogen ratio in wood chips, you need what I see as unfathomable amounts of composted manure. Vegetables need to have the delicate balance of their Carbon to Nitrogen ratio (C:N) preserved at 30:1 or lower. Fresh wood mulch has over 3 times that much carbon! If you’re putting that much composted manure in your garden anyway, skip the work of the wood chip mulch altogether. (And the composting of the chips to get it even close to a carbon level that is workable.) A nice layer of compost will give you big beautiful veggies AND suppress weed growth.
In mulches with a C:N ratio greater than 30:1, not enough nitrogen is present in the mulch to support microbial growth, so microbes scavenge what they need from surrounding soil, outcompeting plants in the process. In mulches with a C:N ratio less than 30:1, the amount of nitrogen in the mulch exceeds microbial requirements, leaving more for plants. –Source
My Experience: Nitrogen Deficiency in Peppers
Two years ago, chippers came through our area. I know that wood mulch is a great mulch for perennial systems (like an orchard) I made sure we had them drop off several truckloads. The grassy patch of lawn where it was dumped ended up being a small converted to gardening space the following year. We carefully scraped off all of the wood chips, raking up as much as we possibly could. These wood chips were never tilled in. The pile only ever sat on top of the ground.
We grew 100′ beds, 30″ wide and the chips had spanned a little over 2 beds. I planted jalapeño peppers down the one row (center of the frame.) Basil grew in the bed to the left of the peppers. You can see it flowering. And to the left of the basil were tomatoes.
As the season progressed you could see an almost perfect circle where the chips had been! The plants were all yellow and stunted. Being a lighter feeder, the basil in front of the tomatoes weren’t as affected. There are daisies in the foreground, followed by the stunted peppers, followed by peppers grown in the exact conditions/variety as the peppers that are stunted. (Same variety, started at the same time, transplanted at the same time, fertilized at the same time with cold-pressed fish emulsion.) It’s not easy to see the tomatoes because of the focus and the basil, but the ones directly next to the peppers stayed a couple feet shorter than the rest and produced probably close to half the yield.
There Is NO One Sized Fits All Approach To Gardening
We need to be talking more about micro-climates instead of USDA zones. We need to be talking about testing our soils and replacing depleted nutrients to improve the nutrient density of our vegetables. Wood chip mulching is being billed as the one-size-fits-all solution to garden problems. But the real problem is that what works for one plot, even short term, might not work on your neighbors garden AT ALL.
You know, it’s ok if someone chooses to garden in a different style than you. I’ll NEVER attack any particular organic gardening method (Ahem. “Back to Eden”). I’m simply sharing why we’ve chosen not use wood chip mulch on our garden after I jumped on a bandwagon when I heard about it in the beginning. My goal is to help those considering wood chip mulching to at least make an educated decision.
Some Trees Are POISONOUS To Other Plants
Here’s your new word for the day: Allelopathy
Allelopathy is “the suppression of growth of one plant species by another due to the release of toxic substances.” So unless you are 100% certain what trees are in your wood mulch, you might inadvertently kill your tomatoes. Where we live there are black walnut trees everywhere. And should the tree trimming service have that in the mix, my tomatoes are toast!
Sawdust mulch, fresh sawdust or chips from street tree prunings from black walnut are not suggested for plants sensitive to juglone, such as blueberry or other plants that are sensitive to juglone. However, composting of bark for a minimum of six months provides a safe mulch even for plants sensitive to juglone.
Juglone can affect blackberry, blueberry, apple, cabbage, peppers, tomatoes, eggplant, potatoes, & certain cole crops in particular.
A few of the other trees that can have an allelopathic effect on plants include hickory, pine, sassafras, and oak. (Oak is known to discourage herbs & grasses in particular… cover crops, anyone?)
Here are some more links you might want to check out:
•Berries & Grapes: Bacterial or Fungal? Some perennial plants (and especially orchard trees) LOVE wood mulch. It might surprise you, but I will be using wood mulch on our homestead! Here is some discussion about different fruiting plants and their preferences. There is also information about which vegetables favor bacterial or fungal soil.
•A Peek Into Our Soil Food Web I show how our hay mulched garden regressed after only 6 months of wood chip mulch. And to be completely honest, I’d take my soil looking like that wood chip mulched section now over the lifeless, heavy clay brick-like soil we’ve got going on at our new home! Repairing this isn’t going to be easy, but I’m up for the challenge. I will be doing it with soil amendments, hay mulching, no-tilling, and radish cover cropping.
The problem, sometimes referred to as “sour mulch” or “toxic mulch,” occurs when mulch is left in large piles and undergoes anaerobic conditions. This results in the production of acids and other compounds that can volatilize when the mulch is placed in beds, especially during hot weather. These vapors can quickly damage annuals and other sensitive plants.
The take-home message is if you DO to experiment with wood chip mulch in your annual vegetable garden, know what trees are in the mix. Let it break down to compost as far as possible. Haul in just as much, if not more, composted manure to use alongside your chips. And respect other gardeners choices if they refrain from joining you.