MUCH time, money, and effort are spent keeping athletic surfaces free of weeds. Not only are weeds a problem aesthetically, but in many instances they can result in decreased field performance and increased risk of injury to athletes. While turfgrass is certainly where we’re most likely to see weeds, they can also appear in other places within an athletic complex, such as the infield of a baseball diamond, sidewalks, parking lots and even on synthetic turf.

In the minds of many who desire to install a synthetic surface, an advantage is the perceived decrease in maintenance compared to natural grass surfaces. The notion that synthetic surfaces are maintenance-free has been long dispelled. A lot of the emphasis when discussing synthetic turf maintenance deals with management of the infill mix. Something else that can be an issue is weed control — an issue that’s addressed both in a preventative manner through proper construction and maintenance, but also curatively either through mechanical means or with herbicides.

How did they get there?

Most fields are installed with a weed barrier underneath to prevent seed germination. Any breaks in this barrier caused by mechanical damage will increase the possibility of weed seed germination. But, even with proper installation and maintenance, there are areas that are prone to weeds, such as near seams or at the edges of the surface.

A field that’s in full sunlight in summer is going to typically be weed-free because it will be too warm and dry to support plant growth. But if any portion of the field is shaded, either by trees or by stadium structures, this increases the likelihood of weed populations. The reason is that a shaded environment tends to be cooler and more conducive to weedy plant survival. Similarly, if a portion of the field is covered with tarps, this can provide an environment favorable to plant growth. The bottom line is if conditions are met to support seed germination, such as ideal temperature and moisture, then seeds of weedy plants may germinate.

Synthetic fields are installed free of organic matter, which is a major reason that these fields have fewer weed issues. However, over time, organic matter can be introduced into the field, and it’s on this organic matter that weed seeds germinate. Windblown dust and soil can be deposited on the field, as can leaf debris. Other sources of organic matter that can be introduced include bird and other animal droppings, or soil brought in on shoes or otherwise by users.

Generally speaking, you’re more likely to see weeds on a synthetic field if it hasn’t been properly maintained or groomed for a period of time. Maintenance of synthetic fields is different than natural grass fields, but just as important in order to get proper performance. Weed control issues on synthetic surfaces are real and can be more common than you might think. Anyone who has seen weeds growing out of a gutter knows that weedy plants can be pretty resourceful.

What weeds?

Basically, anything that can be a weed in turfgrass or in a landscaping bed can theoretically also germinate in synthetic turf, so long as the conditions are right. One thing that might govern which weeds are more prevalent is when a field’s offseason occurs. Since regular grooming is an effective cultural practice, weeds are more likely to occur when regular grooming isn’t being conducted. For example, a synthetic turf field utilized for high school football might have more of an issue with late-germinating winter annual weeds, which then become prevalent in the spring, or also with spring-germinating annual weeds.

Weeds are more likely to be an issue during the offseason, when the field isn’t in play and grooming activities are not being conducted regularly.

What can be done culturally?

Preventative measures include field usage regulations that don’t allow for the introduction of organic material into the field. Dirty cleats and uniforms shouldn’t be permitted. In addition, food, sunflower seeds, chewing tobacco and sugary drinks shouldn’t be allowed.

Knowing what we do about where weeds come from, there are some practices that can be done to the grounds surrounding the field. Since a major source of organic matter contamination of synthetic turf is windblown dust, if possible, try to avoid bare soil areas that are in the direction of prevailing winds. Since some school districts acquire land on the fringe of urban areas, it’s conceivable that the field might be in somewhat close proximity to farm fields. In this or in other cases where windblown soil might be introduced, a strategy – if practical or possible – is to plant an evergreen hedge, such as yew or boxwood, between the source of the dust and the field, which would act in the same way as a snow fence does to knock the dust down. Alternatively, if there is a chain-link fence surrounding the facility, erecting a school banner in a manner so as to block windblown dust could be very beneficial.

Many synthetic fields are in close proximity to plantings of trees and shrubs. In these cases (if possible during the construction phase), the species of tree and shrub to be used should be considered. Since field contamination can be due to both falling leaves and fruits, simply avoiding trees in close proximity to the field is a good strategy. When trees must be planted close to the field, species selection can decrease the potential for this to be an issue.

Trees and shrubs that produce heavy amounts of fruits and leaves should be avoided. For example, a Freeman maple produces fall color that’s similar to a red maple. But the Freeman maple is in most cases seedless, whereas red maples have the potential to produce large amounts of a fruit that can travel for a considerable distance by wind. A large-leaved tree such as a maple may also be a better choice than, for example, a honeylocust, which has very small leaflets that in the fall will filter into both real and synthetic turf. Your state extension service will typically have publications with recommendations for trees that produce less debris (“clean trees”).

If leaves do land on the field, prompt removal via blowing is important. If the leaves are crushed or otherwise incorporated into the infill during the course of a game, this will make removal more difficult later.

As far as cultural practices to follow on a synthetic field, a good preventative measure is regular brushing. The intensity of the brushing done tends to be governed by frequency of field use. But, regular brushing, in addition to leveling the field and keeping the fibers upright, will disrupt weed seedlings quite effectively. Since weeds require some form of organic matter that has contaminated the infill in order to germinate, a good cultural practice is to clean infill material that has accumulated at the edges of the field prior to incorporating it back into the field. Regular deep cleaning in order to remove organic matter should also be conducted.

As with all weed issues, timeliness is important. The longer a problem is left unattended, the more likely it is to become a complicated issue. For a minor infestation, the best option is probably to pull the weeds by hand. What’s important to remember when utilizing mechanical control is that the weed seed probably germinated in organic matter on top of the installed weed barrier, thus removal of the weed should not be performed with a tool that’s going to cause unintended damage to the weed barrier underneath. This can lead to future infestations.

Moss and Algae

  • With many weeds, one option is to simply pull by hand for removal. But since moss is very small and because of the way it grows, hand-pulling isn’t an option. Moss is a weedy plant, but a very primitive plant that typically responds to different herbicides than other weeds. Moss can be problematic because it increases the slip hazard on the surface.
  • Moss and algae are more frequent on low-use areas of fields during times of the year when the rainfall and humidity is high, but sunlight levels are lower. The best strategy to deal with moss is regular grooming. Typically, moss and algae will require specific chemicals and techniques in order to get rid of them.
  • Practices to control moss on other surfaces, such as power washing and/or the use of bleach, should be avoided as this typically voids the manufacturer warranty.

Are there herbicide options?

Reducing or eliminating weeds in the surrounding natural turfgrass areas as well as areas such as parking lots and walkways may also reduce the potential for weed contamination. If a particular type of weed is more of a problem on your field, then more attention should be paid to controlling it in the surrounding areas of the facility.

If you have bermudagrass, quackgrass or other strong creeping grasses adjacent to the field, special attention should be paid to preventing these from encroaching onto the field. These can be a problem because they can follow drainage paths under the field and then send shoots upward. This makes mechanical removal more difficult and usually chemical control is required.

While a properly installed weed barrier will prevent a majority of weeds from sprouting through synthetic turf, over time you may see some infestation, usually along the edges of the field. Weeds can also sprout on accumulating organic matter (dust, leaves, bird droppings, etc.) in the middle of the field.

There are options for weed control using herbicides on synthetic turf fields, but an important rule when doing so is to first consult the installer of the field for a list of products approved for use on that surface.

The advice of the different manufacturers and installers ranges from permitting the use of any type of herbicide to absolutely prohibiting their use. Most recommend certain herbicides. Utilizing an herbicide that isn’t approved may cause damage to the fibers, discolor them or void the warranty. Non-oil based herbicides are most frequently recommended. Also, the herbicide of choice shouldn’t cause staining.

What’s most often recommended in this situations is glyphosate. Of course, there are many other options for herbicides besides glyphosate, but in most cases these have better uses around your facility. Preemergence herbicides, in addition to potentially being staining, are likely not warranted because the infestation isn’t going to be severe enough. Selective postemergence herbicides are also not required. This leaves the other nonselective herbicides and some of those products work more rapidly than does glyphosate. But if the use of these herbicides isn’t approved on synthetic turf, then these products are perhaps better left for use to control weeds in hard surfaces and other surrounding edges of the facility.

In any event, if an herbicide is going to be applied, there are a couple of things to pay attention to. One is that, even though it’s synthetic turf, you still need a commercial pesticide applicators license and all laws and label provisions governing the application of that product must still be followed, including mixing rates, timing of application and posting of notification signs after application. This applies even if you chose and are allowed to use minimum risk products.

The other thing to consider is that just because the manufacturer or installer says it’s permitted to use a particular herbicide, you still have to check the label to make sure that its use on synthetic turf is allowed. Products containing glyphosate tend to have vague labels that allow a wide range of uses. On the other hand, many herbicides used for turfgrass are labelled only for use on turfgrass, or perhaps turfgrass and ornamental plantings. In this case, the use of that product wouldn’t be permitted on a synthetic surface.