Of Mice and Mint (and Mothballs)
Q. James in Oklahoma City titles his email "Mint vs Mighty Mouse and his friends and family" and writes: "Is there any scientific basis to show that planting mint around your house will repel mice and other rodents? This time of year, they're trying to get into the house, of course."
A. The short answer is 'no'. The long answer is that it appears that mint used in a different way really will keep mice from eating your unprotected edibles.
The Short Story: As far as I can research, there is absolutely no proof that any plant in the ground or in a pot will keep insects and/or vermin out of a desired area. Yes, if you planted nothing but strongly scented mints in your garden, there probably wouldn't be any mice in there. But that's very different than protecting a house. You would have to essentially dig a moat around the entire place and fill it with mint, which sounds like too much trouble to protect your supply of Triscuits. And within a few years your entire neighborhood would be overwhelmed with mint and then the mice would no longer be your primary problem.
Let's take this moment to remind and/or inform everyone out there that any plant in the mint family (which includes plants without mint in their name like lemon balm) is difficult to control once planted. Mints are wonderful plants, but when left to grow uncontrolled they are aggressive, invasive, and harder to kill than Mickey's broomstick in The Sorcerer's Apprentice.
Back to mice, neither Mighty nor Mickey. I didn't want to rely on my 'old knowledge' here so I did a fair amount of new research and found an excellent You Tube site called "Mouse Trap Monday" wherein a guy named Shawn Woods is testing everything that people say will repel mice, describing his research projects in depth along the way. These aren't just You Tube videos. These are Citizen Science at its highest level, and they are also fun to watch.
I'll get to his revealing test of mint in a minute, but one of the things that impressed me most were the things he tested that didn't work: Irish Spring (the mice actually ate the horrifically scented soap), the dreaded Carolina Reaper pepper (the mice enjoyed eating that as well), dryer sheets...predator urines. All were a bust.
So you can't fault Shawn for being doubtful about peppermint oil. Previously, people who tried this remedy simply used cotton balls that were saturated with essential oil of peppermint, a highly concentrated aromatherapy product that is widely available. But before he tried it, he found a commercial product from the world's leading producer of mouse and rat traps to test: badge-shaped holders filled with essential oil of peppermint.
For his experiments, he used a specially constructed drawer in a piece of furniture out in a barn. And, like all good scientists, he had two drawers; one containing the supposedly active substance being tested and one that was baited without any repellant. Both drawers had one tiny entrance hole on the side that would allow mice to enter and leave, and both (as per previous experiments) were baited with sunflower seeds, a favorite food of miserable meeses.
The package he purchased had two mint-releasing egg-shaped capsules, which he opened up, pulled a strip to make them active and hung at opposite ends at the test drawer. Then he poured some seeds into the drawer and shut it normally. (I'll let you know why that's important in a minute.) In what I'll call 'the control drawer', he just put the seeds in and then slid that drawer into place. In an additional factor both brilliant and seriously creepy, he had night vision cameras set up to capture the action.
The footage shows mice coming into the drawer with the mint-releasing devices and exiting faster than a vampire in a crucifix factory, while every seed in the untreated drawer was dined upon with fervor. I am therefore convinced that essential oil of mint, placed in the drawers and pantries in which you would normally find evidence of mouse invasion, is a great idea.
And yes, you can grow the mint and use whole branches (crushed up to release the scent) or extract the oil yourself. Be careful if you do the latter, as you should never make direct skin contact with any of these highly concentrated essential oils. Remember to try and contain the spread of your plants, and replace whichever type of repellant you choose every 30 days or so. Or buy the essential oil and do the cotton ball thing, preferably wearing gloves.
More importantly to me, Shawn also provided concrete evidence of the IN-effectiveness of a popular but highly dangerous 'home remedy': Mothballs. Thankfully, he spends the first minute of this video explaining the serious toxicity of these little cancer grenades and warns that it is a violation of Federal Law to use mothballs against mice. But I would NEVER throw this guy under the Federales bus because he proved that they do not work.
Same two drawers. First, he puts one mothball into the corner of each 'true' drawer. (Wear gloves next time Shawn—and have your kidney checked soon!) The mice enter and gorge themselves on the seeds. He tries again, this time using the whole package worth; and he cheats in favor of the mothballs by putting a hard-plastic cover on top to concentrate the fumes. You and I would run out of this deathtrap immediately, but the mice are undeterred, eating every seed.
This doubly reinforces what I have been saying about mothballs for untold decades: Not only should you avoid mothballs because they are more toxic to you than your intended target, but now we also know that they don't work.
Thank you, Shawn; I'm now a fan of Mousetrap Monday!