This Penny Hack Will Save Your Plants from Blight

Updated: Jan. 27, 2023

Don't let the blight that caused the Irish Potato Famine wipe out your home garden. A copper penny might provide the lucky shield you need.

If you’re seeing the telltale brown or yellow spots of blight showing up on your potato or tomato plants, try this unexpected and potential cure: a penny!

Blight-Caused Famine

Blight, caused by fungal spores, can be one of the most insidious gardening problems. It hits plants quickly and spreads easily through the air or the soil. The most famous blight — Ireland’s 1840s Potato Famine — ruined the majority of the potato crop for years and resulted in the death of roughly one million Irish.

Check for Symptoms

Look for signs of blight on plant leaves that may show brown and yellowish spots and wilting. Blighted stems can turn brown or look shrunken. A good first step is to visit your local extension office website. Because blight travels quickly, especially in the wet early and late growing seasons, reporting your blight (and also confirming the diagnosis) can help universities that may be tracking outbreaks and mapping them.

A Penny to the Rescue

It’s important to remove blighted leaves and stems. Dispose of them in a garbage bag so blight spores don’t infect another year’s harvest. After removing blighted leaves and stems, some gardeners will cut a notch into a healthy stem and insert a penny into the notch, believing the penny keeps blight away from the healthy plant. They recommend using only pennies minted before 1983 because those are mostly made of copper, the element considered a natural fungicide. (The zinc in newer pennies doesn’t appear to have the same effect on plants.)

Does Copper Really Combat Blight?

The answer is, theoretically, yes. It may sound like an old wives’ tale, but there is science behind it. Copper, a naturally occurring metal, has long been known for antibacterial and anti-fungal qualities. That made it a longtime choice for water pipes, drinking vessels and storage. Putting copper on a plant to keep away a fungus does make sense.

Some Commercial Fungicides Contain Copper

Anti-microbial copper also factors heavily into the fungicides lawn and garden suppliers sell to eliminate blight and protect your summer harvest.

If you can find a vintage penny, and you have garden plants with blight, give the coin-in-the-stem trick a try. At only one cent each, it’s a frugal fungicide.

Want to Try Other Coin Hacks?

Here are two additional home hacks that make use of extra coins to shim a toilet.