Zoysia grass is a popular choice for lawns across the southern United States and into the transition zone, prized for its dense growth, heat tolerance, and relatively low maintenance needs. However, like any turfgrass, it can be susceptible to weeds. This leads many homeowners to consider using herbicides, and a common question arises: Will Roundup kill zoysia? The answer, unfortunately, isn’t a simple yes or no. It requires a more nuanced understanding of Roundup’s active ingredient, glyphosate, its mode of action, and the specific application techniques used.
Understanding Roundup and Glyphosate
Roundup is a widely recognized brand of herbicide manufactured by Bayer (formerly Monsanto). Its primary active ingredient is glyphosate, a non-selective herbicide. This means that glyphosate doesn’t discriminate between plants; it’s designed to kill virtually any plant it comes into contact with. It’s crucial to understand this fundamental characteristic when considering its use near desirable turfgrass like zoysia.
Glyphosate works by inhibiting an enzyme called EPSPS (5-enolpyruvylshikimate-3-phosphate synthase). This enzyme is essential for plant growth and survival because it’s involved in the synthesis of aromatic amino acids. Without these amino acids, the plant can’t produce proteins and ultimately dies. Because animals and humans do not have this enzyme, glyphosate is often considered relatively safe for them when used according to label instructions.
The non-selective nature of glyphosate is what makes it so effective at controlling a wide variety of weeds. However, it also presents a significant risk to desirable plants like zoysia. If Roundup comes into contact with zoysia blades, it will likely damage or kill them. The extent of the damage depends on several factors, which we’ll explore in more detail.
The Impact of Roundup on Zoysia Grass
The potential for Roundup to harm or kill zoysia is very real. Because it is a non-selective herbicide, direct contact will likely result in damage. The severity of the damage can range from minor discoloration and stunted growth to complete death of the treated area. Several factors determine the extent of the damage.
Factors Influencing Zoysia Damage
Concentration of the herbicide is a critical factor. Higher concentrations of glyphosate will obviously have a more potent effect, leading to more severe damage. Adhering strictly to the manufacturer’s recommended dilution rates is absolutely essential to minimize the risk to your zoysia lawn.
Application method also plays a significant role. A broad, indiscriminate spray is far more likely to result in damage than a carefully targeted application. Using a shielded sprayer or applying the herbicide with a small brush directly to the weed can minimize the risk of overspray and unintended contact with zoysia.
The maturity and overall health of the zoysia grass can also influence its susceptibility to Roundup. Weak or stressed zoysia is more vulnerable to herbicide damage than healthy, vigorous grass. Proper watering, fertilization, and mowing practices can improve the zoysia’s resilience.
Environmental conditions, such as temperature and humidity, can also affect the herbicide’s effectiveness and its impact on zoysia. Warmer temperatures can increase the rate of absorption and translocation of glyphosate within the plant, potentially leading to more rapid and extensive damage.
Symptoms of Roundup Damage on Zoysia
If Roundup comes into contact with zoysia, several symptoms may appear. Initially, you might observe a yellowing or browning of the leaves. This discoloration typically starts at the point of contact and can gradually spread throughout the plant. Stunted growth is another common symptom. Affected areas may appear noticeably shorter and less dense than the surrounding healthy grass. In severe cases, the zoysia may completely die, leaving bare patches in the lawn.
It’s important to monitor your lawn carefully after applying any herbicide. If you notice any of these symptoms, take steps to mitigate the damage. This might involve immediately watering the affected area to help dilute the herbicide or applying a fertilizer to promote new growth.
Alternatives to Roundup for Weed Control in Zoysia Lawns
Given the risks associated with Roundup, exploring alternative weed control methods is often the best approach for maintaining a healthy zoysia lawn. Several options are available, ranging from cultural practices to selective herbicides.
Cultural Weed Control Practices
Promoting a dense, healthy zoysia lawn is the best defense against weeds. This involves proper mowing, watering, and fertilization techniques. Mowing at the correct height (typically 1-2 inches) encourages dense growth that can shade out weed seedlings. Watering deeply and infrequently promotes strong root development, making the zoysia more resilient. Fertilizing according to soil test recommendations provides the necessary nutrients for healthy growth.
Hand-pulling weeds is a labor-intensive but effective method, especially for small infestations. Be sure to remove the entire weed, including the roots, to prevent regrowth. This method is best suited for occasional weeds rather than widespread problems.
Mulching can also help suppress weed growth. Applying a layer of organic mulch, such as shredded bark or wood chips, around flower beds and trees can prevent weed seeds from germinating.
Selective Herbicides for Zoysia
Fortunately, several selective herbicides are designed to control specific weeds without harming zoysia grass. These herbicides target certain types of plants while leaving zoysia relatively unharmed. It’s crucial to choose a product specifically labeled for use on zoysia grass. Always read and follow the label instructions carefully to ensure safe and effective application.
Some common selective herbicides for zoysia include those containing active ingredients such as MSMA, 2,4-D, dicamba, and MCPP. However, it’s vital to check the product label to ensure compatibility with your specific type of zoysia (e.g., Zenith, Meyer, Empire) and to be aware of any temperature restrictions for application.
Pre-emergent herbicides prevent weed seeds from germinating. These are typically applied in the spring and fall to prevent common weeds like crabgrass and annual bluegrass. Common pre-emergent herbicides include prodiamine, dithiopyr, and pendimethalin.
Post-emergent herbicides are used to control weeds that have already emerged. These herbicides are most effective when applied to young, actively growing weeds. It is extremely important to choose a post-emergent herbicide specifically labeled as safe for zoysia grass, as many broad-spectrum herbicides will damage or kill it.
Choosing the Right Selective Herbicide
Selecting the right selective herbicide requires careful consideration of the types of weeds present in your lawn and the specific variety of zoysia you have. Identifying the weeds accurately is essential for choosing an herbicide that will effectively control them. Consult with a local lawn care professional or your county extension office for assistance with weed identification and herbicide recommendations.
Always read the product label carefully before applying any herbicide. The label contains important information about application rates, timing, safety precautions, and potential risks to zoysia grass. Following the label instructions is essential for ensuring safe and effective weed control.
When applying herbicides, it’s best to do so on a calm day with little or no wind to minimize the risk of drift onto desirable plants. Avoid applying herbicides during periods of extreme heat or drought, as this can stress the zoysia and make it more susceptible to damage.
Preventing Weed Infestations in Zoysia Lawns
Prevention is always better than cure when it comes to weed control. By implementing a few simple strategies, you can significantly reduce the likelihood of weed infestations in your zoysia lawn.
Maintaining a healthy, dense lawn is the most effective way to prevent weeds. Proper mowing, watering, and fertilization practices will help your zoysia thrive and outcompete weeds.
Overseeding thin or bare patches in your lawn with zoysia seed or sod can help fill in gaps where weeds might otherwise take hold. Choose a zoysia variety that is well-suited to your climate and soil conditions.
Regularly inspect your lawn for weeds and remove them promptly before they have a chance to spread. Hand-pulling or spot-treating with a selective herbicide can be effective for controlling small infestations.
Avoid introducing weed seeds into your lawn. Clean your lawnmower and other gardening equipment regularly to prevent the spread of weed seeds from one area to another. Use weed-free soil and mulch in your flower beds and vegetable gardens.
Core aeration can help improve soil drainage and reduce soil compaction, creating a more favorable environment for zoysia growth and making it more resistant to weeds. Aerate your lawn in the spring or fall when the zoysia is actively growing.
Specific Scenarios: Using Roundup Responsibly (If Necessary)
While generally discouraged due to the high risk to zoysia, there might be limited scenarios where a homeowner contemplates using Roundup in a zoysia lawn. These situations might involve extremely persistent weeds in isolated areas where other methods have failed. If Roundup is considered, extreme caution and precision are paramount.
Spot Treatment with Utmost Care
If Roundup is used, it must be applied as a spot treatment with extreme care. This means targeting individual weeds directly, avoiding any contact with the surrounding zoysia grass. A small paintbrush or a specialized applicator designed for spot treatments should be used.
Shielding the surrounding zoysia is crucial. Cardboard or plastic shields can be used to protect the zoysia blades from overspray. Even a tiny amount of Roundup on a zoysia blade can cause damage.
Dilution is key. Always use the lowest recommended concentration of Roundup. More is not better; it only increases the risk of damaging the zoysia.
Carefully monitor the treated area for several days after application. If any symptoms of Roundup damage appear on the zoysia, immediately water the area thoroughly to help dilute the herbicide.
Renovation of Heavily Infested Areas
In cases where a large area of the lawn is heavily infested with weeds, and the zoysia is severely damaged, a complete renovation might be necessary. This involves killing all vegetation in the affected area with Roundup, preparing the soil, and then re-establishing the zoysia with seed, sod, or plugs.
This approach should only be considered as a last resort, as it involves a significant amount of work and requires careful planning and execution. It is crucial to ensure that all weeds are completely killed before re-establishing the zoysia. Multiple applications of Roundup may be necessary, with sufficient time between applications to allow the weeds to die completely.
When renovating a lawn, it’s important to address the underlying causes of the weed infestation. This might involve improving soil drainage, correcting nutrient deficiencies, or adjusting mowing practices. Failing to address these underlying issues will likely lead to a recurrence of the weed problem.
Conclusion
In conclusion, while Roundup is a powerful herbicide, its non-selective nature poses a significant risk to zoysia grass. Direct contact with Roundup will likely damage or kill zoysia. Homeowners should carefully weigh the risks and benefits before using Roundup near their zoysia lawns and explore alternative weed control methods whenever possible. Prioritizing cultural practices, using selective herbicides, and preventing weed infestations are generally the best approaches for maintaining a healthy, weed-free zoysia lawn. If Roundup is absolutely necessary, extreme caution and precision are crucial to minimize the risk of damage. Always remember that a healthy and dense lawn is the best defense against weeds.
Will Roundup (Glyphosate) Kill Zoysia Grass?
Yes, Roundup, whose active ingredient is glyphosate, will generally kill Zoysia grass. Glyphosate is a non-selective herbicide, meaning it targets a broad spectrum of plants and doesn’t discriminate between weeds and desirable grasses like Zoysia. When applied to Zoysia, glyphosate disrupts the plant’s ability to produce essential proteins, leading to its eventual death.
Because Roundup is non-selective, careful application is crucial. If you accidentally spray Roundup on your Zoysia, it will likely suffer significant damage or die completely. Avoid using Roundup on or near your Zoysia lawn unless you intend to eliminate it entirely to prepare for replanting or other landscape changes.
How Can I Safely Use Herbicides Around My Zoysia Lawn?
To safely use herbicides around Zoysia, identify your target weeds and select a selective herbicide specifically labeled for use on Zoysia grass. Selective herbicides are designed to kill specific types of weeds without harming the desirable grass. Always read and follow the product label instructions carefully regarding application rates, timing, and safety precautions.
Consider using a pre-emergent herbicide in early spring to prevent weed seeds from germinating in the first place. This can significantly reduce the need for post-emergent treatments later in the season. When applying any herbicide, use a shielded sprayer or carefully paint the herbicide directly onto the weeds to minimize the risk of overspray onto your Zoysia lawn.
Are There Any Roundup-Resistant Zoysia Varieties?
Currently, there are no commercially available Zoysia grass varieties that are specifically bred to be resistant to glyphosate (Roundup). Developing herbicide-resistant turfgrass varieties is a complex and ongoing process, and while research is being conducted in this area, no Roundup-resistant Zoysia has been released to the market.
Therefore, the standard recommendation remains to avoid applying Roundup directly to Zoysia grass, as it will likely cause damage or death to the plant. Using alternative weed control methods, such as selective herbicides or manual removal, is crucial for maintaining a healthy Zoysia lawn.
What Are the Alternatives to Roundup for Weed Control in Zoysia?
Several alternatives to Roundup are available for weed control in Zoysia. Selective herbicides designed for broadleaf or grassy weeds can be used to target specific weed species without harming the Zoysia grass. These herbicides work by targeting unique biological processes found in the weeds but not in Zoysia.
For smaller infestations, manual weed removal is an effective and environmentally friendly option. Regularly pulling weeds by hand or using a weeding tool can prevent them from spreading and competing with your Zoysia. Furthermore, maintaining a healthy and dense Zoysia lawn can naturally suppress weed growth by reducing sunlight and space available for weeds to establish.
What Happens if I Accidentally Spray Roundup on My Zoysia Grass?
If you accidentally spray Roundup on your Zoysia grass, immediate action is crucial to minimize the damage. Rinse the affected area thoroughly with water as soon as possible. The sooner you can wash the glyphosate off the grass blades, the less likely it is to be absorbed into the plant.
Even with immediate rinsing, the Zoysia grass may still experience some degree of damage, ranging from slight discoloration to complete die-off. Monitor the treated area closely over the next few weeks. You may need to overseed or patch the affected area with new Zoysia plugs or sod if the damage is severe.
How Long Does Roundup Stay Active in the Soil After Application?
Roundup (glyphosate) typically has a relatively short residual activity in the soil. It binds tightly to soil particles, which limits its movement and bioavailability to plants. Under normal conditions, glyphosate is broken down by microorganisms in the soil, usually within a few weeks to a few months.
The exact duration of Roundup’s activity in the soil depends on factors such as soil type, temperature, moisture levels, and microbial activity. Warm, moist soil with a healthy microbial population will generally result in faster degradation. However, in colder or drier conditions, the breakdown process may be slower.
Can I Replant Zoysia in an Area Previously Treated with Roundup?
Yes, you can replant Zoysia in an area previously treated with Roundup, but it’s crucial to allow sufficient time for the herbicide to break down in the soil. While Roundup degrades relatively quickly, allowing a waiting period of at least two to three weeks after application is advisable before replanting.
Before replanting, it’s also a good idea to lightly till the soil to help break up any remaining clumps and ensure proper root-to-soil contact for the new Zoysia. Watering the area thoroughly will also aid in dissipating any residual herbicide. Following these steps will help ensure the successful establishment of your new Zoysia grass.