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Gophers and Castor Oil: The Mystery Continues


Ricinus communis ‘Carmencita’: the spectacular castor bean pods almost obscure the inconspicuous flowers, just visible below.

Sad news. Gophers and castor oil do mix. At least in some gardens.

Last report, I was experimenting with saturating some cutting-flower bed soils with castor oil solution. This had worked for me before in my tulip beds, where I didn’t water in summer.

I was also keeping tabs on a friend’s garden: she planted castor bean plants around the perimeter of her garden in New Mexico, and had good results keeping gophers away. Unfortunately, this doesn’t seem to be working in her garden here. Gophers are happily working away amongst these castor bean plants. (They are ‘Carmencita’ plants, by the way, for those of you who just want to grow them because they look so cool.)

I had a theory going for awhile: the studies attesting to the efficacy of castor oil sprays on the soil were done by the University of Michigan. And the woman who recommended it in Gardener’s Supply (a catalogue where I’ve found lots of useful and interesting, well, garden supplies) is also from the midwest.

So my theory was this: in the midwest, where it rains all summer (to excess, this summer), the soil is always moist. The midwest also has a lot of naturally fluffy soil (where it hasn’t been eroded away by bad agribusiness practices). That means that there are green things growing in fluffy moist soil all over. So a gopher has a choice between plants in fluffy moist soil without nasty castor oil, or with it. Any sensible gopher would choose without.

In my dry-summer area, though, the only place you see green plants in summer is where people are watering or where there’s a creek. And while there are some deposits of naturally fluffy soil, they are few. Clay, decomposed granite, and composed granite are the lot of most of us. If we want fluffy soil, we have to work at it. So in my area, if a gopher wants nice fluffy easy soil to burrow through, and moisture and plants, it’s most likely going to find them in a garden. And nowhere else.

The thing that throws a wrench in this theory is the New Mexico story. New Mexico has dry summers, too, and as far as I know is not known for fluffy soil. (If I’m wrong about this, let me know.) So why did the castor bean plants work there? Was it just that the gophers hadn’t found that garden yet? (It does take them awhile.) Or something else?

Life is an ever-turning mystery.

Another friend of mine, who has a master’s in agriculture, gave me some things to think about when I relayed this story to her. Was the type of gopher different in the places where the castor oil was effective? That could be crucial. Do all cultivars of castor bean have the same amount of toxins? It is often true that medicinal plants that are bred to have better looks lose some of the medicinal qualities. (Yarrow is just one example of this.)

I took her advice and delved a little deeper: it turns out the University of Michigan study was for moles, not gophers, and Glenn Dudderer is testing it as a chipmunk and squirrel repellent.

But, you will notice, not as a gopher repellent. And even as a mole repellent, castor oil seems to have gotten mixed reviews: Mole Patrol is now the latest in anti-mole materiel. And even the Gardener’s Supply catalogue now concentrates on moles and downplays the gophers when it comes to castor-oil repellents.




Even though it might not be the heavenly gopher cure-all, castor bean plants are really beautiful. Just be aware that, though the oil is edible, and has many medicinal uses, every other part of the plant is highly poisonous. (In fact, I read a gruesome true story of how a woman poisoned her husband by putting the crushed-up beans in his food. Truly a case of an unfortunate U.S. cultural trait: kill first, talk about it later.) Don’t plant them where small children can investigate the pretty seedpods and attractive leaves.

If you have success in keeping gophers out of your garden with castor bean plants or castor oil, let me know. I’m still trying to figure out why they work in some circumstances, and not others.


Gardener’s Supply catalogue

Herbalhut.com, “Natural Animal Repellents”

Michigan State University Extension: Pests

{ 11 comments… add one }

  • Barbee' August 19, 2008, 9:27 am

    This is an interesting post. I came back to read it a second time. Life is just one challenge after another. To see how well we handle them, I guess.

  • Pomona Belvedere August 19, 2008, 3:42 pm

    Well, whether challenges are about how well we handle them or not–I guess we might as well go for handling them as best we can. Glad you found the post interesting, Barbee.

  • Adam January 11, 2011, 10:34 pm

    Interesting article. We have a large sloped yard in NW Los Angeles and have been clearing the backyard of these towering weeds in order to plant an orchard. We noticed gopher mounds before we planted 15 bare root fruit trees. I treated each hole with castor oil based granules. After treatment I have noticed two mounds dangerously close to two trees. It may be that the gopher got close and tasted the bad soil, but here’s the great mystery. In my research I thought “Why not plant Castor bean plants?” Imagine my surprise when looked up Castor Bean plant and saw photos of the exact same weeds from my yard! Although there is crab grass there too, I am inclined to believe that gophers can exist quite well with Castor bean plants in SW California.

  • GopherChaser January 16, 2013, 3:44 pm

    Gophers invaded my Santee, CA yard after, at my neighbor’s request, I cut down my huge Oleander plants. Oleander is also poisonous to aminals. Nothing has worked to kill them or chase them away permanently. Gopher bait (poison), AMDRO gopher gassers, and noise makers all seem to encourage the gophers to move a few feet away and make new holes and mounds. In fact, they live right next to the noise makers and in the area where castor oil repellant is spread. I once poured concentrated pool chemicals into their tunnerl and it worked…for a few weeks…but the critters came back. I’m going to dig up the grass and fill it in with pebbles and plant castor plants around the perimeter and in front of the house.

  • DemonsDemon April 28, 2013, 8:09 pm

    I stumbled upon a bottle of “Sweeney’s Mole & Gopher Repellent” at the swap meet yesterday and decided to give it a try (it was only a buck). I have been trying to keep my lawn gopher free for the last 4-5 years and had never seen this type of product for sale at any of the usual outlets (fine print on the label indicates that it is NOT approved for use in California, which explains the absence). The instructions on the bottle were pretty vague so I went to the manufacturers site and discovered that the repellent was 100% pure castor oil. The manufacture states that it “soaks into the ground to a depth of 6 inches, eliminating those roots as a food source and makes the critters go away.” This concept sounds good on the surface, but here are a few observations:
    A. castor oil is odorless and nearly tasteless, it is likely that any negative effect a burrowing animal may experience after ingestion would be severe stomach cramps and diarrhea. These symptoms onset in 30 minutes to an hour after ingestion (in humans) so i think it is unlikely that the effect would be associated with a particular cause (the gopher won’t link eating certain roots to causing a tummy ache) and so I don’t expect the detrimental effect to last very long, if at all.
    2. Gophers are vegetarians, moles and voles are insectivores. It is VERY unlikely any single bait/repellent targeting a food source would work well against both.
    3. To those who believe they have castor plants on their property, or are planning on planting castor plants: WARNING: “compounds found on the plant surface can cause permanent nerve damage”. Additionally, because the nerve toxin Ricin naturally occurs in the “bean” of the plant one might expect a visit from Home Land Security following too many purchase inquiries.
    Well, I already invested a whole buck in this Sweeney’s Repellent so I am going to give it a shot. If it works AT ALL, I will update ya’all.
    Ciao fer now.

  • skr July 3, 2014, 9:12 pm

    Please don’t plant castor bean in California. It is a nasty invasive. It is also insanely poisonous. They grow wild in the hills around Los Angeles and kill many dogs every year. Since those same hills are full of gophers, the castor bean plants obviously do nothng to deter gophers.

  • Maggie July 6, 2014, 5:31 am

    We live in southwestern NM and have been using castor oil quite effectively to repel gophers for many years. We buy a five-gallon bucket of “industrial” quality oil from Liberty Natural and mix it with cheap clay kitty litter. Has to be applied again after rain dilutes it. We do all vegetable gardening in raised beds lined with hardware cloth, however. It’s the only way to succeed. The castor oil is for landscape plants.

  • MoleCatcher September 1, 2014, 4:07 am

    This is a lot of discussion around using castor oil to repel gophers and moles – my conclusion (so far…) is that it doesn’t work as a long term solution.

    I’ve heard that castor oil can have a laxitive effect on moles/gophers and does usually work as a repellent for a while. Apparently the key is to make sure it’s applied in the main tunnels so the moles have to come into contact with it.

    The problem though is that at best, the moles/gophers just work around the castor oil or move their home a little further away. As soon as the oil is washed away, they come back. So even if it is effective for a while, it certainly won’t last.

    I’ve opted for a more perminent solution – trying poisons and traps – as I’m not convinced the oil works long term.

  • Elizabeth Baldwin April 25, 2015, 7:13 pm

    I’m just getti g into home made gopher repellent , thanks , what is the ratio of castor oil and corn cob grit or kitty litter OR do you just drop the oil?
    Yeah , Lizzy

  • Deena July 18, 2016, 12:57 pm

    Okay, now I’m confused. What should I do??
    I live in south New Mexico and gophers are taking over at my place.
    We had dogs in the last years and they did a pretty good job in catching them.
    Now my dogs got killed by a nearby road (we live out in the country) and I don’t want to get me another dog. But since they are gone it seems like the gopher population exploded.
    I heard Castor oil granule would work by spreading it over the property and water it. Does anyone know about it? And where can I buy it?

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