Does Companion Planting Work to Deter Pests?

On todays episode we are going to talk about companion plantings such as marigolds and dive deeper into the practice.
What is companion planting? It is the practice of selecting plants that when planted together are beneficial to either one or both of them. Often companion planting has attributed characteristics such as decreased pest presence, increased pollination right through to enhanced flavour. Companion is a form of Polyculture and as a concept has been around since the dawn of agriculture. Much like the advent of agriculture around the world companion planting was discovered independently around the world likely shortly after the initial domestication of crops.
Marigold have lots of claims including being a good companion plant for a wide variety of benefits. A study published in 2009 looked to evaluate the effects of intercropping white cabbage and French marigolds. Cabbage fall prey to many pests. The Polish researchers found that pest damage was lower in plots where the cabbage was inter-planted with marigolds. This held true for a number of different pests. The researchers concluded that the most effective pest control for cabbage was intercropping with pot marigolds. (Jankowska et al.)
In a similar trial focusing the same techniques to see if marigolds could deter pests of snap beans found that Mexican beetle pest damage was reduced when the beans were bordered by marigolds however there was no differences noted when the beans were surrounded by other common companion plants such as pot marigold and garden petunia.
Similarly corn earworms had a variety of results including increased damage to crops when surrounded by companion plants. Leading the researches to determine that companion planting was not a useful control strategy for insect pests in home garden plots. ( Latheff et al.)
Nematodes are a key component of nutrient cycling in soil however about 15% of them are plant parasites and can cause massive crop losses by either the damage they cause to the roots or weakening the plant for other pests. Marigolds can produce a chemical that has the potential to kill nematodes
So planting marigolds in your garden close to plants that are sensitive to nematodes will help keep them away from them? The University of California Riverside discussed this in a paper in July 2007 discussed exactly this. While they confirmed that marigolds can kill nematodes though a variety of situations it’s a very specific species to species relationship and the marigolds generally have to be alive to kill them. In fact there is some evidence to suggest if its not the right pair the marigolds can help increase the populations of other pest nematodes. When using marigolds for nematode suppression its important to research the correct species. Of special note there are other plants that produce similar compounds and when tilled into the soil may still have effective.
I suppose the moral of this story is evidence based gardening. While yes in some cases Marigolds can control both insect and nematode pests it does not always work.

So what I am going to do is take the claims in stride. For instance we are testing the claims of Rock Dust and Biochar in the home garden field trials.
Ill admit I have planted marigolds for the last few years in my garden based on the same common claim that they were good. That said I am open to new evidence and making my gardening decisions based on the evidence presented. Should there be stronger evidence that my practice is not achieving the goals I set out to or is harmful I will changed my practices.
As you know I have promoted the use of leaf mulch, used coffee grounds, Comfrey and Actively Aerated Compost Tea. I will be joining Patricks Trial next year to test the effectiveness of AACT. In order to put leaf mulch, used coffee grounds and comfrey to the test Ill be working on some mini trials and more lab analysis to see whats really going on.
After all we all want to have successful gardens we enjoy right! Why not embark on a journey of life long learning! Is there a Garden practice you were surprised to learn was not correct or did not work in your garden? I would love to know so please put them in the comment section below!

Companion Planting
http://en.wikipedia.org/wiki/Companion_planting
Nematode impacts
http://www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-35.pdf
French Bean Study
http://www.ingentaconnect.com/content/esa/envent/1980/00000009/00000002/art00010
Cabbage Study
http://www.degruyter.com/view/j/fhort.2009.21.issue-1/fhort-2013-0129/fhort-2013-0129.xml
Nematodes
http://msue.anr.msu.edu/news/a_quick_look_at_plant_disease_caused_by_nematodes

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24 Comments

@smilegreen829
May 31, 2025 @ 6:21 pm

Yho we are planters enough with these lecturer tone

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@LifeIsMessyImLearningAsIGrow
May 31, 2025 @ 6:21 pm

Thank you for sharing your garden and knowledge with us. I’m a YouTube gardener too. It’s my 3rd year and ever year I try to get better. This year I’m trying intercropping/companion planting. I found your channel in my research. This is very helpful and I and so happy I found your channel because it has so much to offer. I hope we can learn more from each other as we grow our gardens and our channels!

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@deannabjan8047
May 31, 2025 @ 6:21 pm

On the recommendations of my son, I planted french marigolds. He said it had to be french marigolds not just any marigolds. I enjoyed the splash of color and I do feel it cut down on the number of pests. We have a raised garden and that helped too.

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@philtirah
May 31, 2025 @ 6:21 pm

Being a professional gardener in multiple states now, I'd say yes and no. If you want to deter deer and other vermin this way you have to do waves of plants just like you'd do for visual affect. Often times its the flower or leaves that are either older or younger that deter the pests. It's not just, put a plant in and walk away. You also might be surprised that deer and other pests like your pest controlling plants at different stages of their life cycle.
Then theres always that neighbor or relative who tells you…oh my. The deer and rabbits here dont eat those plants! Well, the pests in their world might not be starving or, might hit have developed a taste for something that isnt neccesarily good for them.
Its It's all trial and error like most farming/gardening/landscaping. I would not recommend giving up though. Keep working at it and researching. I have often found it's the amount of a pest controlling plant a customer has planted. 1 or 2 plants are not going to deter a herd of deer…..or even 1. Lol . Keep trying though. It works.

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@JeeJeanVittoVlogs
May 31, 2025 @ 6:21 pm

Interesting. Thank you for the tips and ideas.👍

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@ithompson79
May 31, 2025 @ 6:21 pm

5 min wasted where he only states that some researchers say yes and others no, wtf?!

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@MsHburnett
May 31, 2025 @ 6:21 pm

Thx my best too is fish + seaweed tea

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@MsHburnett
May 31, 2025 @ 6:21 pm

Nematodes are my least favourites
I now plant chives + old onions throughout my garden

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@karimawilliams3459
May 31, 2025 @ 6:21 pm

thanks.

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@techwizpc4484
May 31, 2025 @ 6:21 pm

I'm planning to add pepper on an elevated bed with coriander already growing on it for almost a year(in fact I've already gathered some seeds), are these two a good combination since I read that coriander is a good insect deterrent? Also is adding wood chips and twigs(not burned) on top of the bed harmful by draining the soil of nitrogen for decomposition or is this only dangerous if the wood is mixed in with the soil? Thanks.

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@techwizpc4484
May 31, 2025 @ 6:21 pm

I'm planning to add pepper on an elevated bed with coriander already growing on it for almost a year(in fact I've already gathered some seeds), are these two a good combination since I read that coriander is a good insect deterrent? Also is adding wood chips and twigs on top of the bed harmful by draining the soil of nitrogen for decomposition or is this only dangerous if the wood is mixed in with the soil? Thanks.

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@knitnpaint
May 31, 2025 @ 6:21 pm

Every time I want to know something, one of your videos comes up in a search. It is the first one I click on. Your information is so good. Did you put the companion planting vidoes of yours in a playlist ?

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@rickschulte8594
May 31, 2025 @ 6:21 pm

hello my trusting garden teacher, just found send watched your 2014 video on companion planting. would please lead me to a video you might have too guide me on this subject for my green garden. thank you my garden friend,Sincerely Rick. Happy winter!!!!!

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@yathatisgood
May 31, 2025 @ 6:21 pm

Did you know that cabbage is a great hyperaccumulator for phytoremediation. Meaning that it is great at absorbing heavy metals from contaminated soils.

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@malcolmt7883
May 31, 2025 @ 6:21 pm

Excellent series on scientifically testing assumptions- There's a ridiculous amount of expert advice that's that's not based on anything but biased opinions. I won't bother with marigolds, but I think that next year I'm going to test out planting a row of dill weed next to my squash since I've heard rumors that squash bugs are repelled by the scent of the dill. It sounds too good to be true, but growing dill is so easy that I'm giving it a shot. Probably plant some 'control' squash in another spot to compare to the others.

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@VegaChastain
May 31, 2025 @ 6:21 pm

I think you (and some in the comments) are confused as to which marigolds are for doing which job. Calendula is known as pot marigold. This is the flower that is used for calming skin irritations and is NOT a 'true marigold' as it is in the daisy family. This is a VERY useful flower both medicinally and topically, but I've never heard of it being used specifically as a companion plant to kill pests (although it does attract beneficials). French Marigold is the superstar of the marigold family – Tagetes patula. *This* is the plant that kills nematodes in the soil and keeps other pesky pests away. If its roots are left in the soil they can deter nematodes for 2-3 years as they decompose.

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@MsQuantized
May 31, 2025 @ 6:21 pm

My experience so far with marigolds is that they haven't shown any positive effect except looking pretty. My brassicas still got eaten. Never thought of trying different varieties I'll do that this year and see what happens

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@redddbaron
May 31, 2025 @ 6:21 pm

There are 2 issues here. Does companion planting work? And does companion planting marigolds work? Marigolds are one species and can not be thought of as the only companion plant. They will help with some things, and not so much others. Other species I have used include basil, oregano, buckwheat, clover, purslane, borage, sunflowers, tarragon, mint, lima beans, pole beans, nasturtiums and on and on. Some of these are not appropriate for some crops and are appropriate for others. You have to think through all the combinations. For example, oregano or a short clover work well with peppers as a ground cover. Nasturtiums are good in the zucchini. The 3 sisters method certainly works and is time tested. Basil does wonders for tomatoes as well as marigolds. Do you grow in a place that tomatoes and peppers need shade cloth? Giant sunflowers can certainly provide shade…just not too many.The trick is to have multi species companions and not just rely on marigolds only. You also need to think about what is happening underground as well. The roots of purslane help corn penetrate hardpan layers. So if you have hard pan, it can help. If you don't have hardpan, then they probably won't be a help. Here is a couple good references. First a cutting edge companion crop/multi-species cover crop vid.

https://www.youtube.com/watch?v=9yPjoh9YJMk

Next basil as a companion plant

http://orgprints.org/6614/

There is a lot more information on my youtube page.

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@bonnywagner4069
May 31, 2025 @ 6:21 pm

In response to Hans: Carpet does in fact protect from weeds and allow water to pass but it does not grow healthy microbes underneath. You would do better with any type of organic matter. Worms seem to really like corrguated cardboard and that will eventually degrade.

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@bonnywagner4069
May 31, 2025 @ 6:21 pm

Your research talks about "Pot Marigold" but I was under the impression the Calendula is pot marigold not the sweet orange and gold ones in your photos.
I had accidentally excellent pumpkins last year that were volunteers that came up among the pole beans and were not bothered by squash bugs as squash in other parts of the garden.

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@adsensedd
May 31, 2025 @ 6:21 pm

Very informative, thanks!

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@priayief
May 31, 2025 @ 6:21 pm

Love your objective approach to growing veggies in backyard gardens! And I appreciate your efforts in posting such interesting and informative topics.

I've been veggy gardening using raised beds for about 9 years. Seven of those years was in Ottawa, ON, Canada (http://en.wikipedia.org/wiki/Ottawa), where I grew (among many other things) brussel sprouts with nasturtiums nearby as well as dwarf Marigolds. The nasturtiums were always infested by aphids. Not a bad thing of course.

Two seasons ago, I moved to the Okanagan valley (http://en.wikipedia.org/wiki/Okanagan) where I set up the same type of raised beds. My nasturtiums failed in both seasons while my sprouts (and broccoli) were infested with aphids (they also attacked my one-season experiment with artichokes). BTW, my regular treatments of insecticidal soap also failed.

In Ottawa I always planted a small section of Marigolds and Nasturtiums in each of my 4' x 4' raised beds. I'm not sure if the marigolds do anything but they look good. I'm hoping that if I can get the damn Nasturtiums to grow, I'll not have an aphid problem with my kale-type veggies.

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@TheAbledGardener
May 31, 2025 @ 6:21 pm

I had started using Humic/Fulvic acid not only in my garden, but to start seedlings. My seeds germinated very quickly and had a positive effect on the plants. Is this something you and Patrick will be testing in the future? I'm looking for a correlation between the benefit of compost tea and the use of humates as compost tea must contain humates at a molecular level.

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@ptrain9020
May 31, 2025 @ 6:21 pm

One year I planted marigolds, and I saw not one single squash bug or egg amongst my pumpkin plants. The following year I did the same and I got squash bugs etc. For me, I don't believe companion planting works like they claim and I rather use the space for growing food instead of flowers.

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Does Companion Planting Work to Deter Pests?

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