Buzz
Thistles are visually appealing but are notorious for being tough, stubborn weeds that are difficult to get rid of. After investing considerable time and effort to maintain and care for your pasture, it’s understandable how frustrating it can be to spot them growing in the field. Thankfully, there are several methods you can employ to eliminate thistles and prevent them from growing back. Some varieties, such as Canada thistle, are trickier to manage, but most wild thistle species can be controlled and eradicated with the right tools. To assist you in this task, we have compiled a list of effective strategies for removing these persistent weeds from your pasture, so you can once again enjoy the pristine land you’ve worked hard to preserve.
Steps
Survey the Pasture at the End of Winter and Early Spring
Search for thistles before they begin to flower. The most effective way to eliminate thistles is to address the problem before they have a chance to grow and spread. The best time to spot thistles is late winter and early spring, when they are still budding and growing in the 'hinge' stage. Take a walk around your pasture during this period to locate young thistles and pull them out before they develop further.
Look for small thistle plants
Thistle seedlings are small, soft shoots that resemble miniature roses. Since the plants are still young, you won’t notice the sharp thorny stems or the flowers like purple or yellow puffballs. The seedlings look like little buds with curly leaves, resembling tiny roses. When inspecting grassy areas, look for these soft shoots exhibiting the described characteristics.
- Some thistle species have prickles or fuzz on their rose-like leaves, while others are smooth.
Use controlled burning for severe infestations
Controlled burning before applying herbicides can be an effective solution for severe cases. If thistles have completely overrun your field, you may consider controlled burning followed by a potent herbicide application for thorough eradication. Be sure to obtain permission for the fire if local regulations require it and have safety measures in place, such as hoses, fire extinguishers, and protective gear. Start the fire in a small area and allow it to spread until the entire field is burned and the fire extinguished.
- If the fire begins to spread to unwanted areas, use hoses or fire extinguishers to control it, such as fire extinguishers.
- Fires can cause significant damage if they spread uncontrollably.
- To create a safety checklist for controlled burning, visit: https://extensionpublications.unl.edu/assets/pdf/ec121.pdf
Manage thistle seedlings with herbicides
The best time to control thistle is when it is still young. Try to target thistle plants that are in the rosette stage and have not yet flowered or produced seeds. Use herbicides containing clopyralid, aminopyralid, or glyphosate and spray directly onto the thistle to eliminate it before it can spread.
- Note: The World Health Organization (WHO) classifies glyphosate as a possible carcinogen to humans. The use of glyphosate is banned in certain countries and states in the U.S. Be sure to check local laws and take safety precautions if using this chemical.
- You can purchase these herbicides at stores that sell plant protection products or order them online.
- Mix the herbicide according to the instructions on the packaging and apply it with your hand or a sprayer directly onto the thistle.
Treat the entire pasture if mature thistle plants are present.
If thistle has already sprouted on the field, other weeds may also be present. Once thistle has grown stems, spot treatments will not be enough to control the entire weed population. Additionally, there may be other weeds on the field. The best approach is to apply a herbicide containing chemicals like clopyralid, aminopyralid, or glyphosate to the entire field to eliminate most weeds, including thistle.
- Identifying thistle before it flowers will help prevent this invasive weed from spreading further.
Trim the weeds for temporary control.
Try mowing the weeds before the plants bloom. While mowing will not eradicate thistle roots, it is a quick and easy method to remove these plants from the field. You can limit their spread if you mow before the thistles bloom and disperse seeds around.
- After mowing the thistle-infested field, you can follow up with herbicide treatments to eliminate the thistle completely.
Dig up the thistle patches if they haven't flowered yet.
Use a shovel to dig up the plant and pull it out. If there are only small, isolated thistle patches that are still in their 'hinge' stage, use a shovel to dig down around 8-10 cm to separate the roots, then grab the base of the plant, pull it out of the ground, and discard it.
- If it's a Canada thistle (a type with tall stems, spiny leaves, and purple flowers), the shovel method may not be enough to eliminate them. Small root fragments can regenerate and sprout new plants. You'll likely need herbicide as well.
Try letting livestock graze the thistles.
This method might not be enough to fully control the issue. If you raise livestock on pasture, a simple solution is to let them graze in areas with thistle growth. Livestock can consume all types of weeds, which prevents them from spreading. Cattle will eat new shoots when the thistle grows back, and over time, the plant's roots may weaken from nutrient depletion, causing the plant to die. However, cattle can sometimes be picky eaters and may avoid the thistles.
- Sometimes, livestock may prefer to eat nearby nutritious grasses, inadvertently providing sunlight and nutrients to the weeds, which could make the problem worse.
Avoid letting livestock graze the grass down completely to help the weeds prevent thistles from regrowing.
Allow the grass to grow tall to overshadow newly sprouting thistle plants. If you encounter significant issues with thistles one year, let the grass grow high the following year after treating the thistle field with herbicide. Avoid letting livestock graze in those areas so that grass roots can thrive and compete with wild plants, helping to prevent or reduce the growth of thistles.
Inspect the pasture weekly to spot thistle growth.
A few thistles can quickly spread across the pasture. If you notice a few thistles, take immediate action to remove them. A single thistle can produce over 4,000 seeds. This means that just a few initial plants can grow into hundreds or thousands of thistles within one to two years.
Warning
- Be extremely cautious when using controlled burning methods to eliminate thistles. Take preventive measures and have fire extinguishers and water ready to control the blaze if it spreads beyond your control.
