Tried and True Weed Control
When it comes to controlling weeds in your lawn, chances are that you probably assume it requires the use of pesticides, specifically, herbicides, to get satisfactory results. The use of herbicides, when properly applied, typically provides amazing results. There is a reason that there are so many different products from so many different companies, it’s because they work. We could debate until we’re blue in the face, about the safety of herbicides that we spray on our lawns for ourselves, our furry friends, and the environment, and not come to any agreement. However, there is one thing that we can probably all agree on, which is, that using fewer herbicides is probably a good thing. Reducing our reliance on herbicides can go a long way in battling herbicide-resistant weed populations, which can render herbicides ineffective.
Can your lawn be 100% weed-free without using herbicides?
When it comes to chemical-free weed control, the answer is pretty nuanced. Will anybody’s lawn ever be 100% weed-free? Hard to imagine. Even the most meticulously manicured lawns will never be entirely weed-free. There’s bound to be a weed or two lurking in the turf canopy if one looks closely enough. You can, however, achieve really great weed suppression without the use of herbicides. So how can you prevent weeds from growing, while at the same time reducing the use of chemicals or eliminating them altogether? The answer is through cultural weed management. Although it sounds pretty cool, cultural weed management isn’t anything crazy and doesn’t require you to study up on all of the weeds in your lawn or any active ingredients in herbicides. You are essentially just being asked to employ culturally sound turfgrass management techniques that give your lawn an advantage over those pesky weeds that are trying to invade it.
Does this mean you’ll never have to use herbicides again? Most likely not. For one, if your lawn is seriously infested with weeds, it’s probably best to either completely renovate your lawn and start from scratch or enlist the help of some herbicides to get weed populations back to an acceptable number prior to employing the methods in this post. If you have a smattering of lawn weeds or are just looking to reduce the overall number in your lawn, if not already being employed, cultural weed management is sure to help, what’s more? It’s backed by science. The major areas to be discussed include mowing height and frequency, fertilizing, irrigation, cultivation, and selecting the proper turfgrass.
How can something that your most likely already doing to your lawn, help you in your battle against lawn weeds? It comes down to mowing at the proper height, mowing frequently enough, and returning your clippings to the lawn. Mowing height is the most well-documented cultural practice that affects weed populations, with lower mowing heights always being associated with increased weed populations in turfgrass (Busey, 2003). It may seem cool or desirable to mow as low as you possibly can, but raising that mowing height is almost certain to decrease weed pressure in your yard. Numerous peer-reviewed manuscripts have shown increased crabgrass coverage associated with lower mowing heights (Dernoeden et al., 1993; Dernoeden et al., 1998; Dunn et al., 1981; Hall, 1980; Jagshitz and Ebdon, 1985; Niehaus, 1974; Voigt et al., 2001).
Mowing frequently also stands to reason that it would help reduce weed populations. Two things are happening with frequent mowing, you're not allowing the weed to flower (hopefully) and the weed (mostly broadleaf weeds) will hopefully not tolerate the continual defoliation like your lawn does. Not allowing the weeds to flower will cut down on weed pressure coming in from new seeds being made by plants allowed to follow due to mowing less frequently. Because your lawn’s main growing points (called crowns) are protected at the bottom of the plant at the soil surface, they’re protected from injury when you mow. Many broadleaf weeds do not have this luxury and will not be able to survive the repeated mowing.
According to the literature, returning your clippings to your lawn has an inconclusive effect on weed populations. Returning clippings to warm-season grasses has been shown to increase weed incidence, specifically in St. Augustinegrass and bermudagrass (Colbaugh and Knoop, 1989). This may have something to do with the removal of weed seeds when you bag your clippings. Returning clippings to Kentucky bluegrass and perennial ryegrass helped reduce weed incidence (Heckman et al, 2000; Harivandi et al., 2001). The thought is that mulching your clippings can help cover exposed soil, which is what weed seeds need in order to germinate and thrive in your lawn. The increased nutrient boost from the decomposing grass leaves may also give a jolt to your grass, increasing its competitiveness. If you haven’t been returning your clippings and are struggling with some weed control issues, try mulching and returning the clippings. The weed control isn’t going to happen overnight, but it’s worth a shot, and it’s less work than bagging.
The key to reducing herbicide usage is to tip the scales in favor of your lawn. This can be done through the proper selection and application of lawn fertilizer. If you’re staring at a yard that is a 50/50 mix of what appears to be turfgrass and a bunch of broadleaf weeds, applying fertilizer and hoping that your lawn will magically start out-competing the weeds is probably a pipe dream. That situation probably requires breaking out the big guns (herbicides), to get the weed population under control prior to utilizing fertilizers. Nitrogen fertilization has been shown to reduce crabgrass populations in Kentucky bluegrass (Dunn et al., 1981; Johnson, 1981; Johnson and Bowyer, 1982; Murray et al., 1983), tall fescue (Dernoeden et al., 1993; Voigt et al., 2001), and Chewings fescue (Jagschitz and Ebdon, 1985). Fertilizing with increased nitrogen also resulted in less dandelion coverage over a 4-year period (Johnson and Bowyer, 1982), and higher nitrogen fertilization suppresses broadleaf weed growth, in general (Haley et al., 1985; Voigt et al., 2001). It is important to note that all of this talk of fertilizing requires that the fertilizer be applied at the correct time of year. Applying fertilizer to dormant grass is not only a waste, it can increase weed populations. For instance, cool-season turf naturally grows fastest in the spring and the fall. Applying high nitrogen fertilizers to cool-season turf in the dead of summer is not advised, as the growth potential for the grass is extremely low, and the crabgrass we are trying to eradicate will gladly accept the fertilization. If you want to apply some fertilizer to your cool-season lawn throughout the summer consider products with low levels of nitrogen like Darker Green or Lawn Energizer Shots of nitrogen on cool-season grass should occur in the spring and fall, while the grass is actively growing. Applying fertilizer too late in the year on warm-season lawns can actually feed the winter annual weeds about to pop up rather than nourish your lawn. Always keep in mind what kind of turf you have in your lawn and the best times of year to fertilize that specific type of grass.
Irrigation management can play a big role in preventing weeds from colonizing your lawn. There are two schools of thought when it comes to irrigation, light and frequent vs. deep and infrequent. Light, frequent irrigation applications keep the upper portion of the rootzone moist. Deep and infrequent irrigation allows for drying of the upper rootzone and soil surface between irrigation events. When you think about what seeds need to germinate, the first thing that probably comes to mind is moist soil. Light, frequent irrigation is keeping the weed-seedbed moist for longer periods, increasing the likelihood of seed germination. By choosing to irrigate with larger amounts, less frequently, you’re making the seedbed less hospitable for germination of weeds seeds. You’re also allowing for increased oxygen diffusion into the soil by allowing the upper portion of the rootzone to dry out before irrigating again. Deep and infrequent can mean different things to different people with different soil types. For someone on the coast with sandy soil, infrequent could mean every other day, as sands are unable to hold water for extended periods. People with heavy clay soils may be able to go 4 or 5 days without irrigating, as their clay soil has a much greater ability to retain moisture than sand. Figure out how long you can go without irrigating by listening (or looking at) to your lawn. Let it dry and down and experience a little drought stress before you choose to irrigate again and keep track of how many days you can go in between irrigation events, then maximize that without completely frying your lawn.
Cultivation can probably really only help in a meaningful way if two things are true of your lawn. Your soil is compacted and you have a healthy goosegrass (Eleusine indica) population. Goosegrass really thrives in compacted soil with decreased oxygen diffusion. Implementing a solid core-cultivation (aerification) plan can help relieve soil compaction and increase airflow in your soil. This can give your lawn an advantage over the goosegrass. Even if you don’t have goosegrass, implementing some core aerification is a great idea to increase the oxygen flow in your soil.
This one is best suited for complete lawn renovations or new constructions. If you’ve completely lost your lawn or inherited a neglected one, consider starting from scratch. Whether choosing to seed or sod, there are some things that you should consider that can give you a leg up against weeds in the future. Start by simply choosing grass that is well-adapted to your area. This will help it establish quickly and maintain vigorous growth, both of which are necessary for a weed-free lawn. Opting for grasses with increased drought tolerance or cold tolerance will help limit damage to your lawn from abiotic stressors like lack of rain and cold winters. Damage to your lawn from abiotic stressors gives weeds a great opportunity to pop in uninvited.
Before you reach for a bottle of weed-killer, check and make sure that you’re doing everything you can in regard to the items mentioned above. If these are all on the up and up and weeds are still a major nuisance an application of herbicide is definitely warranted. If you’ve just sprayed all of the weeds in your lawn or you’re looking to keep your lawn vigorous and healthy, we have all the products to help with your lawn fertilization needs. Contact us today.
Busey, P. (2003). Cultural management of weeds in turfgrass. Crop Science, 43, 1899–1911.
Colbaugh, P.F. & Knoop, W.E. 1989. Influence of clippings recycling on weed and disease incidence in St. Augustinegrass and bermudagrass. P. 249-251. In Takato, H. (ed.) Proceedings of the 6th International Turfgrass Research. Tokyo, Japan. Japanese Society of Turfgrass Science.
Dernoeden, P. H., Carroll, M. J., & Krouse, J. M. (1993). Weed management and tall fescue quality as influenced by mowing, nitrogen, and herbicides. Crop Science, 33, 1055–1061.
Dernoeden, P.H., Fidanza, M.A., & Krouse, J.M. 1998. Low maintenance performance of five Festuca species in monostands and mixtures. Crop Science, 38, 434-439.
Dunn, J. H., Nelson, C. J., & Winfrey, R. D. (1981). Effects of mowing and fertilization on quality of ten Kentucky bluegrass cultivars. Proceedings of the 4th International Turfgrass Research Conference (pp. 293–301). Madison, WI: ASA, CSSA, and SSSA.
Haley, J.E., Wehner, D.J., Fermanian, T.W., & Turgeon, A.J. 1985. Comparison of conventional and mulching mowers for Kentucky bluegrass maintenance. HortScience, 20, 105-107.
Hall, J.R., III. 1980. Effect of cultural factors on tall fescue-Kentucky bluegrass sod quality and botanical composition. P. 367-377 In J.B. Beard (ed.) Proceedings of the 3rd International Turfgrass Research Conference. Madison, WI. ASA, CSSA, SSSA.
Harivandi, M.A.m Hagan, W.L., & Elmore, C.L. 2001. Recycling mower effects on biomass, nitrogen recycling, weed invasion, turf quality, and thatch. International Turfgrass Society Research Journal, 9, 882-885
Heckman, J.R., Liu, H., Hill, W., DeMilia, M., & Anastasia W.L. 2000. Kentucky bluegrass responses to mowing practice and nitrogen fertility management. Journal of Sustainable Agriculture, 15(4), 25-33.
Jagschitz, J. A., & Ebdon, J. S. (1985). Influence of mowing, fertilizer and herbicide on crabgrass infestation in red fescue turf. Proceedings of the 5th International Turfgrass Research Conference (pp. 699–704). Madison, WI: ASA, CSSA, and SSSA.
Johnson, B.J. 1981. Influence of herbicide rotation treatments on species composition of weeds in turfgrass. Weed Science, 30, 548-552
Johnson, B.J. & Bowyer, T.H. 1982. Management of herbicide and fertility levels on weeds and Kentucky bluegrass turf. Agronomy Journal, 74, 845-850.
Murray, J.J., Klingman, D.L., Nash, R.G., & Woolson, E.A. 1983. Eight years of herbicide and nitrogen fertilizer treatments on Kentucky bluegrass (Poa pratensis) turf. Weed Science, 31, 825-831.
Niehaus, M.H. 1984. Effects of nitrogen fertilizer and mowing height on weed content of a Kentucky bluegrass turf. Research Summary, No. 79. Ohio Agricultural Research and Development Center, Wooster, OH.Voigt, T. B., Fermanian, T. W., & Haley, J. E. (2001). Influence of mowing and nitrogen fertility on tall fescue turf. International Turfgrass Society Research Journal, 9, 953–956.
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