Most of us will probably have heard of the 1980s tip of popping a soluble aspirin into the vase water of cut flowers to extend their life. Or, if you aren鈥檛 quite as old as I am, maybe you will have come across what sounds like a hipster-era rebrand of the same idea, as an early 2010s internet 鈥渉ack鈥� for growing tastier tomatoes. Honestly, some permutation or other of this idea is all over the gardening internet.
The rationale behind this seems to be that what perks up humans must also do the same for plants, and I had always dismissed it as a far-fetched myth 鈥� along the lines of folk remedies that use similar spurious logic to claim that plant fertiliser must also make effective hair tonic. However, to my great surprise, when I looked into the science, there was a lot more to using aspirin in the garden than you might imagine.
Aspirin, or acetylsalicylic acid, is a synthetic derivative of salicylic acid, which is a natural compound found in plants. It鈥檚 why extracts from willow, or Salix, trees, from which salicylic acid gets its name, have been used for thousands of years to relieve pain. But plants don鈥檛 create this compound for our benefit. In their tissues, it serves as a trigger to set off chemical reactions that make them more resilient to environmental threats, such as attack from pests and disease, extremes of temperature and . It鈥檚 like the 鈥渙n鈥� switch to their equivalent of an immune system.
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We now that or misting a wide range of crops in an aspirin solution causes them to behave just as if there were a spike in their own levels of salicylic acid, leading to a of their natural defences.
Perhaps more surprising, however, is that studies have shown aspirin doesn鈥檛 just make plants more resilient, it can also improve the quality of their harvests, from with significantly higher vitamin C to that were larger, redder and higher in antioxidants.
Although exact concentrations and application rates do vary between studies, on average it is roughly the equivalent of one 300-milligram soluble aspirin tablet dissolved in a litre of water, applied to plant leaves once every couple of weeks.
Ironically, the one thing the trial results aren鈥檛 so positive about for aspirin is perhaps its most famous use: on cut flowers. While there have generally been mixed results in trials that used aspirin with a cocktail of other ingredients dissolved in vase water, when tested on its own, it usually fails to beat just pure tap water for flowers like (pictured above) and .
The moral of the story, for me at least? Plants will always surprise you, in all sorts of counterintuitive ways. So keep an open mind about even the weirdest-sounding gardening tips.
James Wong is a botanist and science writer, with a particular interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew, in London, he shares his tiny flat with more than 500 houseplants.
You can follow him on X and Instagram @botanygeek
For other projects visit newscientist.com/maker
