Getting rid of the thistles in my gardens, lawn, and rock border always proves arduous for me during the spring and summer months. I live across from an open field, so the thistle seeds just keep floating onto my property, sprouting more and more prickly weeds. My husband and I tried pulling the thistles out by hand, but the task was tedious at best and painful at worst. Even with thick gardening gloves, the prickles on the weeds poked into our skin. Because I am allergic to most plants, I always broke out with itchy, red welts whenever I got poked by a thistle thorn. I needed a better solution to my thistle problem. Upon doing a little research, I discovered that regular old white kitchen vinegar works as an herbicide.
Originally published on July 2, 2013. Updated on May 27, 2024.
About Thistles
Characterized by their spiny leaves and purple or pink flowers, thistles are a group of plants that belong to the family Asteraceae. While some species of thistles are prized for their beauty and medicinal properties, many are considered weeds and are problematic in gardens and agricultural fields. Thistles can be invasive and compete with other plants for resources such as water, nutrients, and sunlight. The spiny plants can also crowd out desirable plants and reduce biodiversity.
There are many species of thistles whose distribution depends on factors such as climate, soil type, and human activities. Some common species of thistles in North America include Canada thistle (Cirsium arvense), bull thistle (Cirsium vulgare), and musk thistle (Carduus nutans). In Europe, common thistle species include spear thistle (Cirsium vulgare), creeping thistle (Cirsium arvense), and woolly thistle (Cirsium eriophorum). In Australia, the most common thistle species are Scotch thistle (Onopordum acanthium) and variegated thistle (Silybum marianum).
One main reason for considering thistles weeds is that the spiny leaves and stems of some thistle species can be painful to touch and can injure humans and animals. Thistles can spread through their seeds, which are produced in large quantities and can remain viable in the soil for several years. The seeds can be dispersed by wind, water, animals, and human activities such as mowing or tilling. Some species of thistles can also spread vegetatively through their root systems.
To manage thistle infestations often requires a combination of mechanical and chemical control methods. Mechanical methods include mowing, cutting, or uprooting the plants before the flowers go to seed, which can help reduce the spread but may need to be repeated several times throughout the growing season. Chemical control involves the use of herbicides that are specifically effective against thistles. However, the chemical method requires careful application to avoid damaging non-target plants and the environment. Many herbicides are also dangerous for human health. Integrated management strategies that combine both approaches are often the most effective in controlling thistle populations while minimizing environmental impact. Having tried the mechanical method without complete success, I decided to try the chemical method — but with vinegar instead of commercial herbicides.
Vinegar as an Herbicide
One day while perusing my Pinterest feed, I happened across a pin about using household vinegar to get rid of weeds in a stone path. According to the writer at A Garden for the House, spraying regular old vinegar on the weeds kills the plants without the use of harmful chemicals. Vinegar is an herbicide that is truly biodegradable. As a food, I knew that I could use vinegar around my house without worrying about the dangers to my daughter and pets. I was excited to have possibly found a solution to my weed problem that was truly safe for my family. Vinegar is also quite a bit cheaper than chemical herbicides.
Vinegar contains acetic acid, which possesses herbicidal properties. After coming into contact with a plant, acetic acid can cause damage to the cell membranes of the plant and disrupt the photosynthesis process, ultimately leading to the death of the plant. Several studies have investigated the effectiveness of vinegar as a herbicide for weeds including thistles. For example, a study published in the journal Weed Technology found that vinegar at concentrations of 5%, 10%, and 20% could effectively control common lambsquarters, a common weed species, when applied as a postemergence herbicide. Another study published in the journal Weed Science found that vinegar at a concentration of 20% could control common purslane, another common weed species, when applied as a postemergence herbicide. While not specifically focusing on the effectiveness of vinegar as a herbicide for thistles, these studies provide evidence that vinegar can be an effective natural herbicide for a variety of weed species.
After buying a few huge bottles of vinegar and a spray bottle, I proceeded to spray the weeds and grass taking over the rock border and path in the front of my house with straight vinegar. I sprayed every plant that I saw: grass, dandelions, violets, wild flowers, thistles. The next day when I went outside to check on the progress, I was thrilled to discover that many of the weeds were yellowed and wilting. Even more to my surprise, most of the thistles looked completely dead. I sprayed everything again that second day for good measure.
On the third day, I went outside and discovered that most of the small thistles that I had sprayed with vinegar had died and completely disappeared. Excited about my discovery, I started spraying all the thistles in my grass and taking root around my trees. After just one application, the majority of the thistles in my yard disappeared. I had killed the evil thistles taking over my property with a little kitchen vinegar and without the need to pull the prickly little weeds up!
Caveats
The only caveat to using vinegar as an herbicide is that vinegar is not selective. Any plants sprayed with the vinegar will yellow and possibly die. As I quickly discovered, not only did the thistles in my yard die, but the grass around the thistles yellowed considerably. Fortunately, grass is pretty hardy. Unlike the thistles, the grass is still in my yard, just more yellow in color than usual. I am keeping an eye on the progress, but I expect the grass to make a come back eventually. However, in the battle against thistles, I am more than happy to sacrifice a little of my grass.
As for other weeds, the vinegar herbicide works okay. The other plants in my rocks are slowly dying. With multiple applications, I suspect that the weeds in my rocks will disappear completely too. However, for thistles, vinegar is also an immediate death sentence. Even if none of the other weeds die, I am still happy with the results of the vinegar on the thistles. If you too have a thistle problem in your garden or yard, try a little white vinegar. You will not be unhappy with the results!
Thistles in Rocks
Weeds in Rocks
Thistles
Thistles in Grass
To recap, vinegar is an environmentally-friendly method for killing thistles and other weeds in gardens, grass, and rocks. Simply pour some undiluted distilled white kitchen vinegar into a spray bottle. Spray the plants that you want to kill with the vinegar. You may need to spray the plants a few times over a few days depending on the hardiness of the plants. Be careful about spraying other plants as vinegar is not selective and will harm any plants sprayed. After spraying the weeds, rinse the bottle out with water to avoid corrosion. Vinegar is a safe, simple, and effective herbicide, especially against thistles.
References
Duke, S. O., & Dayan, F. E. (2017). Natural compounds as next-generation herbicides. Plant Science, 263, 116-124. https://doi.org/10.1016/j.plantsci.2017.06.012
Gedara, S. R., & Watson, A. K. (2013). Evaluation of vinegar as a potential herbicide for organic agriculture. Canadian Journal of Plant Science, 93(1), 73-82. https://doi.org/10.4141/CJPS2012-071
Gomes, M. P., Delgado, I. F., Silva, A. A., Ferreira, F. A., Ferracini, V. L., & Duke, S. O. (2018). Bioherbicides: Current knowledge on weed control mechanisms. Frontiers in Plant Science, 9, 1423. https://doi.org/10.3389/fpls.2018.01423
Grieve, M. (1971). A modern herbal: The medicinal, culinary, cosmetic and economic properties, cultivation and folk-lore of herbs, grasses, fungi, shrubs, & trees with all their modern scientific uses. Dover Publications.
Hansen, R. (2012). Weeds of the West. University of Wyoming.
Khan, M. A., Abbasi, M. K., & Hussain, T. (2015). Phytotoxic effects of aqueous extracts of Eucalyptus, Acacia and Casuarina on four weed species. Journal of Animal and Plant Sciences, 25(2), 417-425.
McNeill, J., Barrie, F. R., Buck, W. R., Demoulin, V., Greuter, W., Hawksworth, D. L., Herendeen, P. S., Knapp, S., Marhold, K., Prado, J., Prud’homme Van Reine, W. F., Smith, G. F., Wiersema, J. H., & Turland, N. J. (2012). International Code of Nomenclature for algae, fungi, and plants (Melbourne Code): Adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011. Koeltz Scientific Books.
Sharma, A., & Sangwan, S. S. (2018). Herbicidal potential of acetic acid and its mechanism of action: A review. International Journal of Chemical Studies, 6(3), 94-97. https://doi.org/10.22271/chemi.2018.v6.i3c.7025
USDA Natural Resources Conservation Service. (n.d.). Thistle. Retrieved from https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/plantsanimals/?cid=stelprdb1046252
Van Der Kooi, C. J., Pen, I., Staal, M., Stavenga, D. G., & Elzenga, J. T. M. (2015). Competition for pollinators and intra-communal spectral dissimilarity of flowers. Plant Biology, 17(2), 358–367. https://doi.org/10.1111/plb.12287
Image Credits
Getting Rid of Thistles with Vinegar: Green Gardening Tips © 2013 Heather Johnson
Thistle in Rocks © 2013 Heather Johnson
Spraying Thistle with Vinegar © 2013 Heather Johnson
Thistle Dying from Vinegar © 2013 Heather Johnson
Thistle Destroyed by Vinegar © 2013 Heather Johnson
Weeds in Rocks © 2013 Heather Johnson
Spraying Weeds with Vinegar © 2013 Heather Johnson
Weeds Yellowed from Vinegar © 2013 Heather Johnson
Weeds Dying from Vinegar © 2013 Heather Johnson
Big Thistle Dying from Vinegar © 2013 Heather Johnson
Thistle Wilting to Death from Vinegar © 2013 Heather Johnson
Thistles in Grass Dying from Vinegar © 2013 Heather Johnson
Dead Thistle in Grass from Vinegar © 2013 Heather Johnson
Yellow Patched in Grass from Vinegar © 2013 Heather Johnson