Aspirin For Plants: Does It Actually Help?
Many people recommend aspirin for plants, claiming all sorts of benefits. Does aspirin work in the garden? We explore the science!
As gardeners, we all would adore there to be a quick-fix methodology for keeping our plants happy. Some turn to the contents of their home to try to do that, and one thing most of us have in the house is aspirin. After all, aspirin helps us; won’t aspirin for plants help your plants, too?
While there’s still a lot of studies required to determine if it’s actually viable, early information seems to indicate that yes, there’s some validity to this claim. The question is really whether it’s the glowing solution to so many problems that it’s believed to be.!
It’s long been touted by cut-flower arrangers that aspirin will help make cut flowers last longer. But is that true? Can it actually produce bigger, healthier tomatoes? Does it actually prevent some plant diseases or improve drought tolerance in your plants? These claims and others have been made over time.
So let’s dive headlong into the science behind giving aspirin to your plants and clear up what’s known and what’s not. We’ll figure out whether this common medicine-cabinet item should make its way to your gardening supply shelf!
What Is Aspirin?
From its earliest form, what we now call aspirin has been used in a variety of medicinal ways. Its first documented use was in ancient Sumeria, marked down on clay tablets as a curative for fevers. Tribal people in the United States used the bark of willow trees to make a beverage that would ease aches and pains; willow use for a similar purpose was also common amongst the Greeks and Chinese. In other parts of the world, different other plants which contained a particular natural substance were used for similar purposes. This substance is the all-natural predecessor to our modern aspirin today.
But what was that predecessor? That would be salicin, found in most Salix-species plants as well as Spiraea-species plants and a few others. First lab-synthesized in the late 1830s by an Italian chemist named Raffaele Piria, the purified form known as salicylic acid went on to widespread use in medicine. Those of us who aren’t doctors are likely most familiar with salicylic acid as an over-the-counter medication to remove warts from the skin, but it was also used for treating fevers or aches as well.
Aspirin itself made its first appearance in 1897 when Felix Hoffman, a German chemist working for Bayer, first synthesized acetylsalicylic acid. It was touch-and-go at the beginning, though; at the same time as aspirin was being synthesized, Bayer had discovered a new potent medication they were planning on introducing in their cough syrups. We now know that other medication as heroin, a very addictive and very dangerous drug! Aspirin was pushed aside as a result and nearly forgotten about until another scientist at Bayer pressed forward with its development.
The primary differences between salicin, salicylic acid, and acetylsalicylic acid are very small in terms of chemical difference, but vast in terms of utility today.
Salicin tends to carry a number of other organic compounds, plus it’s not uniform in the organic matter it forms in. Some plants have more salicin than others, so getting the right dosage was tricky, and it occasionally might have other risky material in it from the bark it was derived from.
Salicylic acid loses all of the other organic compounds and is a purified form of salicin. This potent medication is used topically to remove or abrade the surface layers of skin. It was originally used internally for much the same reasons as salicin in willow bark was used. However, it caused stomach upset and was known to abrade the stomach lining, making it dangerous while still effective for its intended use.
Acetylsalicylic acid, the active ingredient in aspirin, has a very slight modification to its chemical makeup. That tiny variation makes it less likely to cause gastric issues in human use and has led to its widespread medicinal use as a pain reliever and fever reducer today. But in addition, that slight change made it a viable medication for treating a heart attack, something that didn’t come to light until the 1970s.
The name “aspirin” is reputed to be a blending of three things: “acetyl” to identify it as the new derivative compound, “Spiraea” for the meadowsweet-related plant that the salicylic acid was derived from during the initial creation of the drug, and “in”, a common ending to drug names at the time.
Common Claims For Aspirin & Plants
Beyond modern medicine, aspirin is said to be effective in a number of garden applications. But how effective is aspirin in the garden? Let’s look at the science and see what has been discovered to date.
Aspirin For Cut Flowers
Let’s consider this one first. Many gardeners swear by dissolving an aspirin tablet in water and using that in a vase to water their cut flowers. The claim made is that the aspirin will help the plants last longer.
But in reality, that’s not accurate. Flowers produce callose, a sticky or gummy material that seals up points of injury. Most commercial flower preservatives include sucrose to feed the flowers, an acidifier to neutralize the callose so the plants can continue to draw up their nutrients, and some form of antibacterial or antifungal agent to prevent molding or rot.
Aspirin doesn’t have any effect in preventing callose buildup, which means that the flowers will continue to dry out even if they’re submerged in a vase of aspirin water. The plant seals off its injuries, and no amount of aspirin water will prevent that.
For cut flowers, opt for a commercial preservative for the best longevity. If you can’t get your hands on a commercial preservative, many florists recommend mixing some 7-Up into the water, as it contains both sucrose and citric acid (the latter of which will help reduce the likelihood of mold or mildew buildup), but this only works for short-term periods.
Taking this a step further, using aspirin for preserving Christmas trees isn’t very effective either. While trees do not produce callose the same way that most cut flowers do, they also are more in need of water and sucrose. Aspirin water doesn’t provide any real benefit here.
Aspirin For Pests & Diseases
Many people claim a number of wildly variant things for aspirin in the garden. Among these, there are claims that aspirin can be used as a pesticide and as a fungicide.
There’s some evidence that suggests that at least with a bacterial disease, salicylic acid can play a role in prevention but that it isn’t curative. In one study, scientists from the US Department of Agriculture sprayed a selection of tomato seedlings with salicylic acid spray. After spraying, the plants were exposed to a plant pathogen, specifically the bacteria that causes potato purple top disease. The early spraying of aspirin reduced the spread of the bacteria by almost half.
This was more of a preventative than a cure, though. Applications of salicylic acid (SA) after bacterial infection seemed to have little to no major effect on the bacterial disease, likely because the plant was already infected with the disease. It’s believed that the application of the acid in advance triggered a preemptive systemic resistance in the immune system of the plant that helped to defend it against infection. It wasn’t a cure for the plant as much as an immune system boost.
Later research determined that many plants naturally produce SA at the infection sites for various systemic plant diseases. This does not fight the infection directly, but instead triggers an immune response from the plant. Plants sprayed with SA will develop their own natural response to fighting the pathogen.
In a 2019 study, it was determined that while SA is effective for triggering the systemic acquired resistance response, it was not without its drawbacks. It has a short lifespan in plants as they synthesize it quickly. Further, an excess can actually be toxic to the plant.
Remember, all of this is about salicylic acid itself, not aspirin. The active ingredient in aspirin, acetylsalicylic acid, has not been tested or studied in the same way as SA has. As a result, it’s uncertain whether using aspirin in the garden will have any immune system boosting response like that of salicylic acid, or whether it will have similar toxicity levels to plants if overused.
For pests, there’s been even less research to support that claim. In many cases, once something is believed to prevent diseases, it’s mistakenly assumed to prevent pests as well. That doesn’t seem to be the case here. There’s no indication that an immune system boost in the plants as a response to the salicylic acid application will provide any natural resistance against pest attack. While a healthier plant is often less likely to be under attack, that doesn’t mean that using aspirin in the garden as a pesticide would be effective, particularly since it isn’t even an antifungal.
So to sum this one up: while it’s possible that one could use aspirin tablets dissolved in water to prevent some bacterial plant diseases (although it hasn’t been proven to be effective and requires more research), it’s not really a pest deterrent.
Aspirin For Rooting Plants
This idea originates with the earlier salicin forms that salicylic acid, and later acetylsalicylic acid, were derived from. It was believed that by cutting up a large quantity of willow and soaking it in water, you would naturally produce a material that could be used to help plants develop roots more quickly. Willow water, as it was referred to, became a common additive in garden uses as a result.
The problem with this concept is that aspirin is not known to be a rooting hormone. There are only a couple of naturally occurring rooting hormones, and these are referred to as auxins. Auxins slow down side-budding and encourage root development. Probably the most common in the average gardener’s arsenal is Indole-3-butyric acid, as it’s by far the most popularly used in powdered rooting hormones.
Some limited testing has been done to see if SA has an effect on root growth, but it hasn’t proved to be conclusive.
At least one 2008 study on sunflower seed germination was done to see if acetylsalicylic acid (ASA) or SA were effective in promoting larger root growth in the newly-germinating seeds. Extremely minute amounts of SA or ASA produced a lengthening of early embryonic roots, but the more SA or ASA was added, the worse the results became. With higher quantities, the seeds had major negative impacts, and at the highest dose the seeds failed germination — the additive caused them to simply die out. Overall, it was generally disproven to be of use.
While there is no current study article out there that says “don’t use aspirin as a rooting hormone”, it’s clear that it has no real benefits in that way. It’d be better to allow the plant’s own system to handle rooting, or perhaps provide a little bit of Indole-3-butyric acid if you want to offer a real auxin as an aid. Aspirin is not your best solution here.
Aspirin For Plant Tolerances
Can you improve the drought tolerance of a given plant with the use of aspirin? How about its heat or cold tolerance?
Some signs hint that this might actually be true. While salicylic acid is more often examined for this role, acetylsalicylic acid may also be effective at improving plant tolerances to various issues.
The effectiveness of using aspirin in this way goes back to SAR, mentioned earlier: systemic acquired resistance. Just as aspirin triggers the plant’s defense systems against bacterial infections, it can trigger the plant’s defense systems to stimulate it to protect itself from other conditions.
Here’s the problem, though: while results have shown that this does in fact work, it’s no real replacement for caring for your plants properly. Consistent feeding, watering, and maintenance of the leaves and stems of your plants will give you a better effect than you’d get if you sprayed aspirin water onto them.
Further, when you use aspirin in this way, you still run potential risks in the garden. Remember that an aspirin water spray has short-term effects for immune-boosting and that it’s just not a long-term viable solution. Properly care for your plants, provide a cold frame during cold weather and shade cloth during hot weather, water them consistently, and you’ll have overall better production and you’ll know it’s working.
Aspirin For Tomatoes
Now we reach the final claim: aspirin for tomato plants. Some claim that you can use aspirin to improve yields, get healthier plants and heartier leaves, and generally improve all elements of this popular plant.
The results on this are a bit mixed, truth be told. A master gardener from the University of Rhode Island did some testing in her vegetable garden in 2004, using an aspirin spray on cucumbers, basil, beans, and tomatoes. Her claims as to the effects were incredible: she said that the plants were much bigger, more vigorous, and had huge fruit. She also claimed that diseases were cured when plants were sprayed with aspirin water.
As you might imagine, this caught a lot of attention very quickly. In fact, her report of her “discovery” was published in multiple newspapers and became heavily cited.
The very next year, a doctor of plant sciences at the University of Rhode Island worked with the master gardener to do a slightly more scientific test. As a result, they found that there was not a reduction in yield on Early Girl tomatoes if aspirin or SA were used to trigger systemic acquired resistance. Unfortunately, the test found that more testing in a much more in-depth fashion would be required to get accurate measurements, as there was a lot of variability in the results they were getting.
Does it work? Maybe. We don’t really know yet; there hasn’t been an update on this particular line of vegetable garden study since 2005. But we do know that the Rhode Island master gardener’s initial glowing review of aspirin in garden uses was very anecdotal. Until her experience can be reliably reproduced in a way that we know how to use it, aspirin spray likely isn’t going to be a huge benefit to your tomatoes or other vegetable plants.
Overall, it seems as though a spray of aspirin solution may have some effects on plants. Whether those are beneficial effects for your plants still remains to be seen, however. It’s not a tomato miracle drug, it certainly doesn’t help with sunflower germination or rooting, and while it may help with systemic responses, science still hasn’t found whether that will work in the long term.
To me, this is a sign that there’s a lot more research to be done yet on the topic before we know if there are really any benefits for gardening use.
Science is a slow process, and we have a lot to learn still. I wouldn’t rule out future interesting information coming to light. But for now, I have to recommend against aspirin in everyday gardening use, if only because of how little we know. That may change in the future, particularly with more research into SAR, but for now, skip this home remedy in your gardening endeavors.