Spraying plants with dissolved aspirin boosts their immune system and health.
Aspirin spray isn't a proven plant tonic. There's a real kernel. Salicylic acid does switch on a plant defense response, and aspirin did it in the lab. But sprayed on, it's often toxic to the plant, it breaks down fast, and a dose that works on one crop won't carry to another. Treat aspirin as a curiosity, and don't make it a routine.
What is actually known
There is a real phenomenon underneath this. Salicylic acid is a signal plants use to switch on systemic acquired resistance, a real defense response, and that role was first found when salicylic acid and aspirin made tobacco resist a virus. But that is a long way from "dissolve an aspirin and spray." Applied from outside, salicylic acid is often toxic to the plant, is broken down quickly and does not last; the same dose does not act the same way from one crop to another; and field-scale studies are still needed to judge whether it works. It is an interesting real mechanism. It is not a garden tonic to count on.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
The key role of SA in plant defense was first reported when SA and aspirin induced resistance of tobacco against TMV
In plants, SA acts as a signal molecule that kicks off a series of reactions that help defend against external threats.
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Cite this page
Milpa Gardens. "Spraying plants with dissolved aspirin boosts their immune system and health." Evidence grade: Contested. https://milpa.garden/beliefs/aspirin-spray-aspirin-plants/
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