Zoysia grass is a popular warm season lawn grass known for its ability to stand up to heat, drought, heavy foot traffic and a variety of other challenges. However, zoysia lawns are not immune to weeds. There are several methods available for keeping weeds out of zoysia grass.
Pre-emergent Herbicides
Applying pre-emergent herbicides is one of the most effective ways to prevent weeds in zoysia grass. Pre-emergent herbicides work by creating a chemical barrier just below the soil surface that prevents weed seeds from germinating. When applied properly in early spring, pre-emergent products provide season-long control of crabgrass, goosegrass and other summer annual weeds.
There are several pre-emergent herbicides labeled for use on zoysia lawns, including prodiamine, dithiopyr and pendimethalin. It’s important to select a product specifically intended for zoysia grass and follow label instructions carefully, as some pre-emergents can cause turf injury if misapplied. Applications should be made before soil temperatures reach 55-60°F to get the maximum length of weed protection. Granular formulations are easier to apply evenly than liquid products.
Post-emergent Herbicides
Post-emergent herbicides target weeds that have already germinated and emerged from the soil. These products come in two main forms – selective herbicides that kill specific weeds without harming zoysia grass, and non-selective herbicides that kill all plant material. Selective post-emergent products containing active ingredients like atrazine, metsulfuron-methyl, Celsius and Revolver are useful options for spot treating broadleaf weeds and certain grassy weeds in zoysia.
Non-selective herbicides like glyphosate (Roundup) can also be applied as spot treatments by carefully spraying only on the weeds and avoiding contact with the zoysia blades. This works best on young, actively growing weeds. Mature weeds with extensive root systems often regrow after glyphosate applications. Always use a surfactant or sticker-spreader with glyphosate for best results.
Cultural Practices
Proper mowing, irrigation, fertilization and other cultural practices create an environment where zoysia grass can thrive and outcompete weeds. Here are some tips:
- Mow frequently at the proper height – 1-2 inches for most zoysia cultivars. Longer mowing heights promote deeper rooting.
- Leave grass clippings on the lawn to return nutrients.
- Water deeply and infrequently to encourage deep roots.
- Fertilize at least once per year, ideally in early summer.
- Dethatch and aerate periodically to alleviate soil compaction.
- Overseed thin or bare areas to prevent weed encroachment.
Hand Pulling
Manually removing weeds by hand is often necessary as a supplement to other control methods. Hand weeding allows you to remove weeds selectively without risk to the zoysia grass. It also eliminates mature weeds that may be resistant to chemical control. Hand pull weeds after rain or irrigation when the soil is moist and the entire root system can be removed more easily. Use a sturdy tool to dig out deeply rooted perennial weeds.
Organic Weed Control
Vinegar (acetic acid) is a popular organic herbicide that provides effective control of some weed species. Use horticultural vinegar with 10-20% acetic acid concentration. Be aware that vinegar lacks residual activity, so repeat applications are needed on emerged weeds. Some studies suggest corn gluten meal can inhibit germination of small-seeded annual weeds when applied pre-emergence. Corn gluten meal breaks down into nitrogen fertilizer to feed the zoysia.
Preventing Weed Spread
To avoid introducing new weeds, it’s important to start with clean seed, sod or plugs when establishing zoysia grass. Be diligent about removing weeds from planting beds and surrounding areas before they go to seed. Also clean mower blades after cutting infested lawns to prevent spreading weed seeds to clean turf. Avoid tracking weeds from neighboring properties by keeping foot traffic to a minimum when zoysia is stressed and vulnerable.
Common Zoysia Weeds
Here are some of the most problematic weeds that infest zoysia lawns:
Crabgrass
This fast-growing annual grass thrives in full sun. It produces long sprawling stems with wide leaves and purple seed heads. Heavy infestations give lawns a thin, patchy appearance. Crabgrass is best prevented through pre-emergent herbicide use. Post-emergent herbicides like quinclorac, fenoxaprop and MSMA provide some control of young crabgrass plants.
Goosegrass
Goosegrass emerges later in summer than crabgrass but is otherwise very similar. The prostrate stems radiate out from a white center point, resembling a goose foot. Goosegrass is controlled by the same pre- and post-emergent herbicides as crabgrass. Starting in spring, herbicidal soap can help manage small goosegrass plants.
Virginia Buttonweed
Virginia buttonweed has round, green leaves arrayed in pairs along creeping stems that root at the nodes. Small white flowers form in summer. Manual digging can help control buttonweed, but it spreads rapidly from any fragments left behind. Post-emergent herbicides containing metsulfuron provide the most effective chemical control.
Dallisgrass
Dallisgrass is a perennial clumping grass with long tapered leaves and tall seed heads. Pre-emergent herbicides don’t control dallisgrass since it spreads mainly through rhizomes and stolons rather than seed. MSMA and certain sulfonylurea herbicides work well on actively growing dallisgrass. Repeat applications are needed to control regrowth from underground stems.
Nutsedge
Yellow and purple nutsedge are common warm season perennials that produce dense clumps of grass-like leaves. They spread rapidly via tubers that form on roots extending underground. Post-emergent sulfentrazone provides effective chemical control. Hand removal can also be successful if tubers are eliminated.
Broadleaf Weeds
Common broadleaf weeds like dandelion, plantain, clover, wild violet, spurge and oxalis are easily controlled in zoysia lawns using selective post-emergent herbicides containing 2,4-D, dicamba, MCPP or similar active ingredients.
When to Apply Herbicides
Timing is critical when using herbicides for zoysia weed control:
- Pre-emergents – Apply before soil temperatures reach 55-60°F. This prevents germination of warm season annual weeds.
- Post-emergents – Treat young, actively growing weeds according to label directions.
- Spot spray – Target individual weeds as needed during the growing season.
- Avoid summer stress – Don’t spray when zoysia is struggling with heat, drought or disease.
Weed Identification
Proper weed identification ensures you use the right control methods for each species. Consider characteristics like:
- Leaf shape, width, venation
- Stem growth habit – upright, prostrate, stoloniferous
- Flowers or seed heads
- Presence of rhizomes, tubers or creeping stems
- Growth rate and life cycle
Use weed identification books and online resources to match unknown weeds with photos and descriptions. Your local extension office can also help identify specimens.
Lawn Care and Maintenance
A healthy, dense zoysia lawn is your best defense against weeds. Proper maintenance practices strengthen the grass so it can outcompete invaders. Here are some key tips:
Mowing
- Mow frequently at 1-2 inch height.
- Leave clippings for free fertilizer.
- Use a sharp blade for clean cuts.
- Avoid scalping or mowing when wet.
Irrigation
- Water deeply and infrequently.
- Allow soil to dry between watering.
- Adjust for weather and growth rate.
- Avoid frequent, light watering.
Fertilization
- Fertilize at least once per year.
- Use a complete fertilizer with N-P-K.
- Time applications for peak growth periods.
- Follow label rates carefully.
Aeration
- Core aerate annually or as needed.
- Relieve soil compaction from traffic.
- Enhance air, water and nutrient infiltration.
Dethatching
- Remove thatch layer if over 0.5 inch deep.
- Use a dethatching rake, vertical mower or power rake.
- Overseed bare areas after dethatching.
Organic Weed Control
Organic weed control uses natural methods to suppress weeds without synthetic chemicals:
Corn gluten meal
- Pre-emergent weed control
- Blocks root formation in germinating seeds
- Breaks down into nitrogen fertilizer
- May require multiple applications
Vinegar
- Post-emergent control with horticultural vinegar (10-20% acetic acid)
- Burns foliage of contact broadleaf and grass weeds
- No residual activity, repeated use needed
Soap-based herbicides
- Made from fatty acids derived from plants
- Kill small, actively growing weeds on contact
- Some residual control depending on formula
Boiling water
- Kill weed seedlings and soft growth with boiling water
- Avoid plant injury through precise pouring or spraying
- Best for spot treatment of driveway and sidewalk weeds
Mulching
- Blocks light to prevent weed seed germination
- Use 2-3 inch layer of organic mulch like wood chips or bark
- Keep mulch back several inches from grass blades
Hand weeding
- Manually remove weeds at the roots with tools
- Labor intensive but highly selective
- Use sturdy tools for deep taproots
When to Hire a Pro
Severe weed infestations often require professional help. Consider hiring a lawn care company if:
- Weeds cover over 20% of the lawn’s area
- Multiple weed species are present
- Perennial weeds have extensive roots systems
- You don’t have the right equipment or experience for the job
- Lawn is too large to tackle in a reasonable time
- Pre-emergent timing is already missed
- Previous control efforts failed
Licensed pros have specialized tools, chemicals and knowledge to attack weed problems quickly and effectively. They can also apply pre-emergents at the right time to prevent many weeds from invading in future years.
FAQ
What is the best pre-emergent for zoysia grass?
Prodiamine, dithiopyr and pendimethalin are effective pre-emergent options labeled for use on zoysia. Apply before soil temperature reaches 55-60°F.
When should I apply weed killer to zoysia grass?
Apply post-emergent herbicides to actively growing weeds as needed during the growing season. Spot treat weeds instead of blanket applications. Follow label directions.
How do I get rid of grassy weeds in zoysia?
MSMA and sulfonylurea herbicides work well on grassy weeds like crabgrass and dallisgrass in zoysia. Quinclorac and fenoxaprop also provide post-emergent control. Pre-emergents prevent many annual grassy weeds.
What is the best fertilizer for zoysia grass and weed control?
Look for turf fertilizers formulated specifically for zoysia. Avoid over-fertilizing, which can fuel weed growth. Apply at recommended rates and intervals for your specific lawn.
What is the easiest way to get rid of weeds?
Pre-emergent herbicides provide the easiest control by preventing many weeds from germinating in the first place. Hand pull small weeds when possible. Spot treat with post-emergents. Maintain healthy turf density to suppress weeds.
Conclusion
Controlling weeds in zoysia grass involves integrating proper mowing, irrigation, fertilization and soil care with targeted herbicide applications. Pre-emergent weed preventers in spring provide the foundation. Post-emergent herbicides spot treat any weeds that emerge. Organic options like corn gluten and vinegar can also be effective. With vigilant prevention and control, zoysia lawns can stay lush and weed-free.
