I’ve used woodchips in the garden for many years. They are great for temporary paths with a life of a couple of years and some mulching requirements, such as around fruit trees.
My Grandson looking cool on top of one of the woodchip piles
There are not a lot of nutrients in woodchips, but they do add carbon to the soil as well as improving structure and increasing humus. When you need to rot woodchips down, basically to compost them, it can be difficult. Compost, to rot well, needs a balance between carbon rich materials, also called ‘browns’ and nitrogen rich materials, also called ‘greens’.
Image from Wikipedia of yew, Taxus baccata
Adding some woodchips to a compost heap with an abundance of nitrogen rich greens can help balance the carbon nitrogen ratio, and the size of the chips helps aeration by preventing compaction.
With a pile of woodchips just left to themselves, they will rot down in time, but to speed the process it is necessary to add nitrogen. Woodchips are basically just carbon. The nitrogen source can be chemical, urea or sulphate of ammonia or natural, bloodmeal or urine.
What if the woodchips are poisonous?
One question I’d not considered until now, was ‘what if the woodchips are poisonous?’.
So when I received this email in response to a newsletter from ‘Woodcrafts’, some research was in order.
Incidentally, Yew is very poisonous. Just eating 50 grams of yew will likely kill you. Animals have been found dead with yew still in their mouth.
Yew trees can often be found in churchyards. I believe planting them there was a way of ensuring the grounds were respected. With a yew tree there, people had good reason to keep their animals from trespassing.
Hi John,
Thanks for the latest email with advice on allotments etc. I was particularly interested in this one for the feature on using woodchips.
I am a professional woodturner so produce a lot of small woodchips; something between sawdust and wood chips. I have used this both as a mulch and in my compost but, a tip I was given some years ago, was to save urine and pour that over the woodchips to help replenish the nitrogen. It seems to work but wondered if that is wishful thinking on my behalf or if there is any genuine science behind the idea.
I appreciate it’s not the most pleasant topic to discuss, and it is easier for us males to collect it, but might be of interest to other gardeners.
I do also have a question. I turn yew and laburnum, both of which contain toxins. Do you know if those toxins would remain active in mulch and/or my compost, so could be taken up by plants? Some have said the toxins would break down in the soil, others have said they wouldn’t trust fruit and veg grown with that compost/mulch around them.
Unfortunately the internet is becoming so unreliable, I prefer to ask real, knowledgeable people.
My answer:
Urine, being a good source of nitrogen, will certainly help wood chips rot down and ameliorate nitrogen robbery from them when used in paths next to a growing bed.
If people think urine is bad, they’ll love a book I just read on Humanure by Joseph Jenkins. His well-researched conclusion was that, with care, perfectly safe to compost and eventually feed the veggies. He’s been doing it for many years and lived to write about it.
A fascinating question – thank you!
With yew it was fairly easy to find a published scientific paper that applies. Basically, the toxins degrade in composting so not a problem. They won’t translocate via veggies so they’ll be safe. If the toxins degrade in compost, I’d expect them to do the same in soil over a couple of years if not composted.
See this paper: https://pubmed.ncbi.nlm.nih.gov/20579691/
Not so easy to find the answer on laburnum, but I would think that Cytisine, being a naturally produced compound, would decompose in composting and in the soil. The fact that it is being considered as a medical compound (smoking cessation aid) and as an insecticide implies that it isn’t bio-accumulative and subject to translating into the food chain.
People do love to panic about things! And wouldn’t “Deadly yew chips may pollute food chain” make good clickbait!
You used to get diversity of opinion online, but it’s being swamped by scraped rubbish and AI generated waffle. I actually tested an article I wrote and one generated by AI. The AI had a number of factual errors and some nonsense, but was very readable. Putting both online, Google preferred the AI.
Happy to take comments on this topic, especially if they’re evidenced.
Yew were often in church yards as they would fence off.
Sorry Pete, don’t quite understand your comment.
John,
What I think Pete intended to say — because it is what I was going to say — is that yew trees were planted in churchyards in medieval times. This was because they needed yew wood for their bows. The church graveyard is one of the few truly stock proof enclosures in a medieval village, and thus by consensus the best place to grow your bows.
Aha! I read they grew yew in churchyards, so people would take care to keep their livestock out. Long time ago and casual piece, so your explanation is probably more correct.
Very interesting, I’ve always avoided putting privet woodchip/cuttings into my compost heap for the same reasons. It’s considered by some be toxic to other plants. Do the toxic compounds break down as they rot?
Hi Rob
Privet contains a toxic glycoside so eating any part of the plant is harmful to humans, dogs, cats, horses and I understand some other mammals. Birds can eat privet berries without being affected.
Composting, especially hot composting, will break down the glycoside, as will just leaving the cuttings in a pile until the twigs break down.
I’ve composted privet for many years and not had a problem with the resulting compost. I’ve been told that privet is harmful to plants, but I don’t think it’s factual. Thinking back, we had a flower border bounded by a privet hedge and the flowers did really well.
My old cat uses wood pellets litter and I have been using that for years to add to compost heap and as a mulch. It certainly improves the soil structure and rots down well (yes I do remove the solids!).
Me too, Pauline. The scooped solids go down where ours go, and the fairly urine-rich (nitrogen source to balance the carbon) is used as a mulch or mostly as a carbon source in compost.
Great minds think alike! 🙂
I used fresh woodchips as a weed suppressing mulch around my gooseberry and raspberry beds in late Spring. Based on your comments John, should I be
mixing in some nitrogen rich material ( grass mowings perhaps?) to balance the carbon?
Hi Roger. Well, nitrogen robbery from wood chip mulches isn’t as bad as I thought. The reason is that the interface between the wood and the soil isn’t as much as it would be if the wood chips were mixed into the soil.
Having said that, mixing in grass clippings can’t do any harm but won’t make much difference except the wood chips will rot down a little faster.
Bodily functions have been a topic of revulsion for year. However with urine being essentially sterile when produced it contains a brilliant mix of plant nutrients, mother nature is a perfectly circular ‘economy’ and nothing is wasted. Easy to collect, especially for men, and when diluted a perfect fertilizer. Why we choose to use drinking water to flush away a domestically produced nutrient mix is beyond me.
Hi Stuart
Ignorance and fear! I’ve had people email that I was spreading dangerous misinformation when I’ve said urine is sterile and people would get disease from following me. Very annoying, especially when I had double-checked my facts with a GP!
I have a laburnum, privet hedges and a yew clipped to a pyramid which probably came from a cutting my mother acquired from the Fortingall Yew (look it up for the facts, myths and legends surrounding this ancient specimen).My uncle and aunt lived in the next village. I have composted the clippings for the last 50 years and have spread the resulting materials widely on the vegetable garden. There have been no obvious ill effects on people, plants or worms and other compost residents. Many of the garden plants can be toxic to humans especially those derived from the nightshade family but cultivars such as potatoes, tomatoes and aubergines are safe to eat. So don’t eat what you’re not supposed to and compost properly using urine and lime and you will probably be the better for it.
I have used mixed wood chippings including yew for many years but mainly compost the chips first in piles with added urine. After a year or so I seive the material twice; first through a 1″ mesh then through a 1/2″ mesh (a bit labour intensive). The fines go into home made potting compost with leaf mould, garden compost and soil (or whatever handy), the middles go into the compost heap or as general mulch and the coarse material goes on paths. I’ve had no problems with veg growing.