Roundup is a popular herbicide used to control weeds in landscapes, gardens, and agricultural settings. The active ingredient in Roundup is glyphosate, which works by inhibiting enzyme pathways necessary for plant growth. Glyphosate is absorbed through the leaves of target plants and translocated throughout the plant, eventually leading to plant death.
Roundup is available in several different formulations, with the most common being a concentrate that must be mixed with water prior to application. Homeowners typically use Roundup concentrate at a dilution rate of 1-2 fluid ounces per gallon of water. The use rate can be increased for tougher weeds.
Roundup is widely used because it provides broad-spectrum control of many annual and perennial grass and broadleaf weeds. It also has no soil residual activity, meaning it will not linger in the soil and damage future crops or ornamental plantings. Roundup is considered a post-emergence herbicide because it is most effective when applied after weeds have germinated and are actively growing.
Can Roundup freeze?
The short answer is yes, Roundup concentrate or mixture can freeze under the right conditions, just like any other water-based liquid. Roundup contains glyphosate along with various surfactants and additional inert ingredients in an aqueous solution. When temperatures drop below 32 degrees Fahrenheit (0 degrees Celsius), the Roundup liquid can freeze solid.
Freezing is most likely to occur when Roundup concentrate or spray mix is left outdoors in cold temperatures. If left undiluted in its original container, Roundup concentrate may freeze during winter weather or even an unusually cold night. Similarly, previously mixed Roundup left in a spray tank or other container can also freeze in cold conditions.
The diluted version of Roundup that homeowners typically spray is also susceptible to freezing. Even if the concentrate itself does not freeze, spraying a dilute Roundup solution when temperatures are near or below freezing can lead to frozen herbicide on plant leaves.
Is it harmful for Roundup to freeze?
Freezing Roundup does not normally cause any harm or damage to the product. The active ingredient, glyphosate salts, along with the inert surfactants and other ingredients are stable when frozen and will not degrade. Once thawed, frozen Roundup will return to its normal liquid state.
Most Roundup products contain propylene glycol that acts as an antifreeze to lower the freezing point and help prevent freeze damage. For example, one Roundup Concentrate label states the product will freeze around 5 degrees Fahrenheit (-15 C). Even if freezing occurs, the Roundup solution will return to normal once thawed.
Roundup can undergo multiple freeze-thaw cycles without any loss in efficacy. In fact, you can even spray thawed Roundup that was previously frozen. The herbicide activity will not be reduced.
That said, any separation that occurs while frozen may remain after thawing. Be sure to mix or shake thawed Roundup well before using to evenly distribute the ingredients. Also, allow thickened concentrate to fully return to its normal consistency before diluting in water for spraying.
Can you spray Roundup after it freezes?
Yes, you can safely use and spray Roundup after it has frozen with no reduction in effectiveness. As mentioned, the active ingredient glyphosate and inert ingredients in Roundup remain stable when frozen.
The most important factor is thoroughly mixing or shaking the container after thawing to evenly distribute any ingredients that may have separated. Follow the label instructions for proper mixing and dilution rates when preparing to spray previously frozen Roundup.
Test spray a small area first if you have any doubts about how well mixed a previously frozen batch of Roundup is. Check for normal herbicide effects on target weeds. But in most cases, you can expect full weed control from thawed Roundup.
You do need to be cautious about spraying Roundup when ambient temperatures are near or below freezing. The spray can freeze on plant foliage before being adequately absorbed. Wait for warmer temperatures before spraying thawed Roundup to ensure proper activity.
How to prevent Roundup from freezing
While Roundup will not be harmed if frozen, you can take some simple steps to help prevent freezing temperatures from affecting your supply:
- Store concentrate indoors when temperatures drop below freezing.
- Keep diluted Roundup spray mix from freezing by storing indoors or in a heated space like a garage.
- Spray when daytime temperatures are above freezing so solution does not freeze on plants.
- Do not store containers directly on cold concrete; elevate off ground.
- Place concentrate container in a bucket or cooler and surround with straw, towels, or other insulating material.
- Move concentrate and spray mix containers to a warmer area if extreme cold is forecast.
Taking preventative measures allows you to avoid the inconvenience of needing to thaw frozen Roundup later. It also reduces the chances of separation and the need for extra mixing or shaking before use.
If you do end up with frozen Roundup, simply move it to a warmer area and allow it to gradually thaw. Avoid excessive heating. Gently agitate or mix the thawed solution to evenly distribute ingredients before dilution or use. Then proceed as normal with your weed control needs.
Signs that Roundup has frozen
How can you tell if your Roundup supply has frozen? Here are some signs to look for:
- Roundup concentrate takes on a slushy, ice cream-like texture and consistency.
- The liquid becomes solid and difficult to pour from the container.
- Diluted Roundup in a spray tank orjug appears slushy or frozen solid.
- Crystallization, layering, or separation of ingredients is visible.
- The contents pull away from the container sides or container shape is distorted.
Roundup often takes on a cloudy, thickened appearance when frozen then thaws to a clear solution again. Compared to water, Roundup takes longer to fully thaw due to the antifreeze ingredients. Check the spray tank or nozzle for clogs if spraying thickened Roundup.
While Roundup can withstand freezing with no problems, the container may crack or break if left frozen for an extended time. Prolonged freezing is best avoided when possible by storing Roundup properly during cold weather.
Effects of spraying frozen Roundup
Spraying diluted Roundup that is frozen or near-freezing can negatively impact weed control performance. Here are some potential issues:
- Poor coverage – Frozen spray droplets won’t adequately stick and coat plant foliage.
- Reduced absorption – Weed leaves may not properly take up the herbicide solution.
- Slower visual effects – Weeds continue growing for longer before showing damage.
- Lower efficacy – Less complete weed kill compared to warmer Roundup application.
- Needs re-spraying – Weeds may require an additional spray while growing to achieve control.
The best practice is to always apply Roundup-based herbicides when air and plant temperatures are above freezing. Wait for warmer temperatures to spray if Roundup concentrate or diluted solution has frozen.
Leaf surfaces often become waxy in cold conditions, contributing to reduced Roundup absorption. Aim for daytime spraying once temperatures climb above 50-60°F for maximum effectiveness on weeds.
Does Roundup expire after freezing?
Roundup herbicide concentrate or diluted solution can be safely stored after freezing without any effect on the expiration date or shelf life. Freezing does not cause Roundup to expire sooner or degrade the active ingredient, as long as it is thawed correctly.
Be sure to follow the storage instructions on the Roundup packaging. Most Roundup products will remain effective for at least 2 years when stored in original containers above 25°F (-5°C).
As long as the concentrate has been stored according to label directions, freezing one or more times will not impact the expiration as long as it is thoroughly agitated after thawing.
Of course, allowing any chemical product to freeze repeatedly over many seasons does increase the chance that separation or other issues could occur. Follow usage and storage guidance for best retention of product quality and expected shelf life.
But in general, you can use Roundup even years past a single freeze as long as it has been stored properly otherwise and mixed well upon thawing. Do not use if solid crystals remain after mixing or if you notice changes in appearance or performance during use.
Can freezing damage the container?
While the Roundup concentrate itself will not be harmed by freezing, the container could potentially be damaged by expanding liquid and ice crystals. Plastic packaging is most susceptible to cracking, splitting, or bursting under freezing conditions.
Roundup concentrate sold in metal or plastic drums could also see damage from freezing and thawing cycles over time. Check containers closely for leaks, cracks, or other defects if they have been frozen.
Use caution when thawing to avoid putting direct heat on Roundup containers. Microwaving frozen Roundup could cause severe container damage and is not recommended. Slow warming to above freezing is best to limit risks.
Transfer concentrate to a new compatible container if you see damage or are concerned about the integrity after freezing. Wear proper protective equipment when transferring any chemical product.
Conclusion
Roundup herbicide can safely withstand freezing temperatures without any reduction in efficacy or life span as long as it is stored and mixed properly after thawing. While the Roundup solution may freeze solid in cold conditions, the active ingredient and other components do not degrade when frozen.
Take simple preventative measures like indoor storage when below freezing to avoid needing to thaw Roundup later. If Roundup does end up frozen, allow it to gradually warm above 32°F and mix thoroughly before diluting or spraying. Avoid applying frozen or near-freezing Roundup to maximize weed control. Follow all label directions and guidance for best performance.
