I’ve discussed my dislike of cardboard mulch before: like other sheet mulches it restricts water and gas transfer between the soil and atmosphere. In published comparison studies, other mulch choices generally outperform cardboard in terms of plant growth, weed control, etc. But there’s one area where cardboard is tops compared to every other mulch material tested.
Termites LOVE cardboard. Did you know that termite researchers use cardboard feeding stations to lure termites? And cardboard is often used as the “control” in feeding studies, because termites will always eat it?
People seem to think that wood chips are termite magnets. Though termites can eat some types of wood, they prefer cardboard in taste testing. If they are given no choice and have only wood to eat, they will consume it but their survival rate decreases. Dead termites don’t reproduce.
To give termites a bit of a break, they are very useful in bringing life back to crusted, arid soils: studies have shown that just adding mulch and termites to these degraded soils is enough get biological processes going again.
But personally, I’m not providing a cardboard welcome mat for termites to the gardens surrounding my wooden house. Hopefully you won’t either.
Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets.
Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019).
In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award.
"The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors
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29 thoughts on “Why I don’t like cardboard mulch”
Just curious, I’ve been saving up bundles of newsprint for weed-killing mulch. Would you think it would have the same appeal to the termites, as cardboard?
I live in the South Puget Sound area.
Cardboard appears to be the favorite food – one researcher called it the “junk food equivalent.” But they also like all kinds of paper.
The process of making paper and cardboard removes a lot of the chemicals that might repel or injure termites, which is why wood is often not chosen for food.
(As an aside – newspaper is even worse for blocking air and water movement into the soil. Anaerobic microbes, like those that cause root rots, thrive under these conditions.)
This is very interesting information, Linda. I see a lot of recommendations for using cardboard and/or newspaper to control weeds and used paper on a newly dug border myself years ago. I thought the poor results in that border was from some other factor such as water, poor fertilizer choices, etc. when in fact it may well have been from the newspaper mulch. Interesting, indeed! Thank you for this insight.
What do you recommend (if not sheet mulch) to kill a lawn that I am replacing with high desert appropriate plants? Thanks!
Nadine, I did a post on this a while back: http://gardenprofessors.com/how-to-get-rid-of-your-lawn/. Has photos and everything. Our entire landscape is lawn-free now.
Hi Linda, could you please update the link for this post? Is now a 404/ not found site. Am really interested to know what you did!
Hi Rebecca –
Ah, now I see what you’re referring to. Will do.
I’ve never tried cardboard. Tried newspaper to smother grass and not very satisfied
– got messy, some grass grew through the newsprint and the paper took a long time to decompose. Now if I’m at my leisure I just pile up a big bunch of leaves or other mulch. If I’m in a hurry, I use Roundup.
Over here in Sweden people throw trash every on the ground all the time. It rains so much here that I’ve noticed it disintegrates extremely rapidly. I’ve never used either newsprint or cardboard as mulch. I have no problem shredding it and applying it to Vermiculture process. Once again COARSE MULCH is my choice. Before I left San Diego 6 years ago, I had my mum’s woodland garden soil so biological active that we had to apply heavy layers of mulch serveral times a year. I’m not sure what’s going on now, but all those wonderful nutrients being uploaded into all those trees and shrubs. Something was working over time under that soil.
termites need water more then anything.
My cardboard has no termites, it is not near any house(I have 10 acres). The next lot over has a brick house. My problem is that the cardB. is not killing the Bahia grass, it just runs until it finds light, sometimes ten feet away.
Just because cardboard is attractive to termites does not mean it increases the chances of having the
m infest nearby structures if you use the material. That is quite a leap, considering how pervasive is this species.
Cardboard mulch has its uses and research only takes you so far because there are just so many variables.
For established trees the gas exchange issue would probably be of no consequence if you are using cardboard under woodchips in an area much less than the spread of the roots. I doubt that exchange inteference lasts more than a couple of weeks anyway, at least in humid regions, because moist cardboard is attractive to worms and they rapidly eat many holes in it long before it loses efficacy in stopping aggressive weeds from poking through it and the mulch.
In the humid northeast I believe paper under wood mulch is useful in increasing it’s weed prevention qualities- particularly when using loose arborist chips which don’t stop weeds as well as shredded wood unless you lay it very thick.
Of course, shredded wood has its own problems as it tends to mat up tightly which, while stopping weed growth, also prevents water permeation.
If all you are trying to do is stop weeds in a small circle around the base of an established shrub or tree, this can be a good thing.
University-based websites (like PestSense at WSU) caution people against keeping wood piled near their house to prevent termite infestation. Given that termites like cardboard so much more than wood, it’s not a leap at all to assume cardboard near a house or other wooden structure would also be risky.
There’s also substantial research demonstrating the superiority of chunky mulch over sheet mulches. I’ve posted about this before, so I’m not going to try the patience of our regular readers. But feel free to check the review article I wrote about it; it’s embedded in my post on May 12, 2010. (linked to my name above)
One of the missions of this blog is to provide science-based information. If and when substantial research to the contrary is published, my recommendation about cardboard mulch is not going to change. (We also encourage people to use some kind of identifier so we can respond to you directly.)
Linda to my mind wood against the house is much different because you are providing termites with a beach head directly against the house. I would still need to see the research to even be certain this was a scientifically based concern or a leap of logic by people who happen to be scientists. However, as I recall, part of termite control is keeping structural wood from touching soil- concrete is the safer interface. So, of course, you wouldn’t want pile wood or dirt against a house.
Research is subject to interpretation that is not necessary scientific even if the interpretation is done by a scientist. The theory that cardboard poses a threat of termite infestation is not in any way scientific unless there is research that has drawn a specific correlation as, of course, you know.
If scientists were infallible at interpreting research they’d always agree.
The reason this point is worth arguing about is that cardboard is something that people usually have around and in northeastern conditions it is quite useful for weed control in some circumstances when used under a couple of inches of wood chips. West coast research about paper creating problems may be meaningless here as paper under chips doesn’t tend to dry out in our conditions. It also doesn’t, in my experience, tend to create termite colonies.
You recommend using 4″ of wood chips and have stated that research shows that that depth is what is needed to be affective. If you are mulching more than a few trees or shrubs that starts to require a lot of hauling. Personally I use about 40 cubic yards of wood chips and shredded wood to mulch my small nursery, landscape, personal vegetable garden and orchard. If I used 4″ it would be 80 yards- probably over 2,000 large wheel barrow trips on uneven terrain (I didn’t do the math but at least it would feel like 2,000 trips!).
If I can get the same control using half the chips and a layer of cardboard I think you know what I’ll be doing.
That’s unfortunate for people with termit problems. I’ve used cardboard mulch (2-3 layers under a thick layer of organic matter like straw or wood chips) at many different gardens over the years and had no problems, either with unwanted insect life or gas-deprived soil and roots.
So this comment is only mildly related to your post. The research you talk about – could you provide a link or links to it? I have to start an IPM program at the school where I work, and this kind of information would be really helpful. Cardboard clutter is a major problem, so if I can remind folks of ways to not create pest conducive conditions around the building or in their classroom, and put a ‘name’ of ‘face’ to the pests they’re preventing, I think that would help. Thanks for this interesting information. I sure wish I could get my hands on loads of free chips like you can up there! Around here, we have to fight to get them, going so far as to out-bribe (with cookies and such) the neighbors to get chips from Asplundh. I have no idea what they do with all those chips!
@Jam, the research I refer to is just a compilation of published papers that I found doing a literature search. It’s not a single publication. The best thing I have is my mulch review paper (which is not just on cardboard), embedded in my June 21 comment.
Interesting…I’ve been considering using some paper bags between my rows of vegetables since my neighbors took my woodchips for their chickens…might have to see if I can go get even more woodchips or something.
I’ve been composting cardboard for years and find that the worms break it down so fast the termites don’t have a chance to get at it (not that I mind them, I’ve got nothing for them to infest). Then I just mix that compost with layers of dead leaves and shredded tree trimmings before I lay down the mulch. Its worked really well to as sheet mulch kill off most of my lawn and prepare it for planting as well as to winterize the garden.
Linda, we’ve been researching cardboard mulch assuming that the only issue is what kind of cardboard. Then I stumble on to your post here. Our situation is a new house with no lawn and the usual grass and thistle colonizers taking over the otherwise lifeless dirt. We’ve been burning the weeds and had planned on laying down cardboard, then topsoil, then letting it sit all winter. Next spring we’d start landscaping using mostly native plants with some vegetable plots. Do you think we could follow this same plan using wood chips (as described in your lawn-killing post)? Or do we need to re-think the whole thing?
Mike, I think the wood chip mulch method would be perfect for your soil. I’d start with an inch or so of compost over the bare soil, then cover and protect that with several inches of wood chips. If you decide to go this route, I hope you’ll take photos to document your relative success.
I live in NJ and that does not seem to be the case here. There favorite spots seem to be larger wood chunks rotting roots and stumps.
Robert, they may live in rotting stumps, but they prefer processed paper products to raw wood. Easier to digest.
I have been using cardboard under bark or gorilla hair mulch for my small pathways between raised bed boxes in my backyard. This year the plan was to do the same with my main pathway, hoping that a thick layer under the mulch would deprive evil bindweed of any sun. (I have been digging shoots of bindweed for over a year, cursing letting the first sighting of this weed get a foothold because I thought it was morning glory and no big deal. Little did I suspect it was an extremely invasive weed with roots that end just short of the Earth’s magma.)
Though that path starts about 20 feet from the house and I have not attracted termites so far, all my raised beds are redwood and I do not want it to be a secondary snack when the cardboard breaks down to nothing before the next spring.
Any recommendations to starve the bindweed without testing my luck with avoiding termites? I am in Sacramento, CA.
What about newspaper? Have been reading much lately about newspaper as a cost-effective option that frugal people pursue. Do termites dwell on that? It’s true that wood chip mulch doesn’t attract termites nearly to the degree that the stereotype conveys.
Hang on. You say termites love cardboard and will only eat wood if there is no cardboard available? So then mulch with cardboard to keep them away from your house. Why would you not use it? Makes no sense.
Great idea if you want to attract termites. Most people would prefer not to have them.