Salicylic acid, a chemical commonly found in willow trees, is the original basis for what we consider aspirin today. It has been used to help plants develop their roots and survive harsher environments and can even help preserve cut flowers for longer periods of time.
Natural sources of salicylic acid, like white willow bark, have been harvested for thousands of years by locals looking to find relief from headaches and fevers. Salicylic acid is a hormone commonly processed in willow plants, especially when under stress. When added to soil, the chemical has a unique quality of promoting root growth in other plants.
Salicylic acid, or a similar chemical named methyl salicylate, is developed by plants to limit the infection of various fungal and viral illnesses. This is referred to as a hypersensitive response, boosting its immune system and resistances to disease. Researchers at the National Center for Atmospheric Research have discovered that some plants will release methyl salicylate into the air to communicate with neighboring plants and warn them of fungal or viral threats.
Modern aspirin is similar chemically to salicylic acid and will trigger the same immune responses when applied to plants. The most affective way of releasing the chemical is to spray plants with aspirin dissolved in water, where it will then be absorbed by leaf and stem stomata. The chemical will intentionally trigger a strengthening response within the plant.
Cut Flowers & Aspirin
When dissolved in water with cut flowers present, aspirin will block the ethylene production in plants. The eventual death of cut flowers takes place because of a process known as senescence. Ethylene eventually withers and stops chemical processes within plants. Since aspirin blocks ethylene, it consequentially slows senescence and allows the flower to last long. The effectiveness of this process varies with different plant species.
One of the main risks of applying aspirin to plants is an eventual lack of response. Plants that are treated too frequently with an aspirin solution will be constantly wasting energy towards fighting infection. Eventually, growth and flowering processes will become inhibited and the aspirin's effect will fade. This process often quickens with cut flowers that often remain malnourished due to a lack of nutrients.
The dosage recommended by Martha McBurney, head of the University of Rhode Island aspirin experiment, is 1 1/2 uncoated aspirins added to every 2 gallons of water. Two tablespoons of yucca extract added to the solution will help the water stick to the leaves and prevents beading. Applications of the spray should take place once every three weeks.