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