No gardener would deny that trying to grow healthy plants has its share of headaches. But did you know that the remedy for one of the most severe – diseases – could very well be sitting on a shelf in your medicine cabinet?
That’s right! When dissolved in water and used as a spray, ordinary aspirin can help you grow healthy plants resistant to the ravages of disease. How does it work?
The answer lies in photochemistry and a compound called salicylic acid (SA). As this 2020 research review from researchers at South Korea’s Andong National University Department of Plant Medicals observes, “increasing reports suggest that SA is indeed a key plant hormone regulating plant immunity.”
Many cultures have known for centuries that willow trees’ inner bark contains salicylic acid, and used it for a variety of medicinal purposes.
Abd the South Korean names specific plants that developed increased resistance to various diseases after treatment with a salicylic acid solution. They include:
- tomatoes and other Nightshade family plants
But what does any of this have to do with aspirin?
Aspirin is the commercial name for acetylsalicylic acid. According to the Pharmaceutical Journal, The Bayer pharmaceutical company chemist Felix Hoffman found that attaching a group of acetyl molecules to the SA hormone made it less irritating to the human digestive system.
Bayer named its new inflammation-blocking discovery”A” for acetyl, “spir” for the meadowsweet spirea flower containing salicylic acid, and “in,” because that’s how many of their drugs’ names ended.
Putting it another way, by extracting natural salicylic acid from plants and converting it to synthetic acetylsalicylic acid aspirin, Bayer unknowingly gave us a cheap, effective tool for growing healthy plants.
What Salicylic Acid Does for Plants
Salicylic acid is a “signal” molecule. Its job is to signal a plant under attack from disease to turn on the genes that build resistance to the harmful pathogens. This reaction, carried out with help from other biochemicals, is known as “system acquired resistance” (SAR).
Picture Star Trek’s original Enterprise computer flashing “Warning: Red Alert.” The SA warns a plant’s immune system of an approaching threat, but too often, the immune system doesn’t react quickly enough to repel the invader completely.
In 2004, gardening writer Thomas Powell (former editor of The Avant Gardener newsletter) wrote that many of his subscribers claimed that dosing plants with a highly diluted aspirin and water solution had remarkable effects on their health.
He suggested that the aspirin tricks the plants into “thinking” they’re under attack. They go into SAR mode even when no disease is present so that when one does move in, their defenses are strong, ready, and waiting.
It’s the botanical equivalent of feeding someone kiwi, so they don’t catch a cold.
Aspirin and Water Recipe for Healthy Plants
Spraying plants with too strong an aspirin and water solution can be toxic. But University of Rhode Island master gardener Martha McBurney reported excellent results with the school’s demonstration vegetable garden.
She added 1.5 crushed, uncoated 325mg aspirin tablets to 2 gallons of water, along with 2 tablespoons of yucca extract to help the solution cling to the leaves. (Plant-based dish soap would work just as well).
Martha sprayed tomatoes, cucumbers, beans, basil, kale, broccoli, and other veggies every three weeks through the growing season. The reward was a garden full of robust, green, healthy plants.
In the case of the cucumbers, she claimed, “We even saw some disease problems that reversed themselves.”
Now that’s some powerful medicine!