Turf colorants for aesthetics and/or as an alternative to overseeding

Turf managers in the southern United States have traditionally overseeded warm-season turfgrasses during the fall in order to maintain aesthetically pleasing playing surfaces as well as playability throughout the period of dormancy. The most significant negative attributes to overseeding are the agronomic and aesthetic challenges of transitioning the playing surface from a cool-season grass back to a warm-season grass while experiencing temperatures that are prone to wide fluctuations.

Overseeding is not the only way of having green turf during the winter months of the year. In recent years, turf colorants have served as the standard for an alternative to overseeding warm-season grasses and as a result, a number of new products have been introduced to the market. The increase in popularity, particularly on golf courses, can partly be attributed to the spring transition from overseeded grasses to bermudagrass, which has become more problematic due to heat- and drought-resistant cool-season grass varieties. Conversely, prolonged cool springs (similar to what we have experienced here in the Southeast the previous two years) have also allowed overseeded grasses to persist through May and June causing delays in bermudagrass green-up. The use of turf colorants allows for a much more predictable spring green-up and contributes to a healthier stand of bermudagrass going into the summer. In order to better understand how a number of these new products visually perform and persist over time, a product evaluation study was initiated at the North Carolina State University Turfgrass research facility in Raleigh, N.C. in November of 2011 and 2012.

Results over the Years

We have conducted numerous studies at North Carolina State University to evaluate various colorant products. Our first detailed studies were applied to putting greens in fall 2008. Subsequent trials have included evaluations on bermudagrass and zoysiagrass at an assortment of mowing heights. In total, we have evaluated more than 30 products. These include products from manufacturers/distributers such as BASF, Burnett Athletics, D. Ervasti Sales, Enviroseal, Geoponics, Harrell’s, J.C. Whitlam Manufacturing, John Deere Landscapes, Milliken, Missouri Turf Colorant, Pioneer Athletics, Poulenger USA, Precision Laboratories, Solarfast, US Specialty Coatings and World Class Athletic Surfaces.

In the earlier studies we applied colorant treatments to completely dormant turfgrass in late October to early November using a boom sprayer and flat-fan nozzles at rates ranging from 40 to 160 gallons per acre (gpa). Applied to bermudagrass, colorant increased turf color from 38 percent to 67 percent relative to the control at the time of painting. Of course there was some variation in how the color was judged over time. But remember the saying “beauty is in the eye of the beholder.” Most of these products will have a date in which they will need to be re-applied to get season-long green color. Over the six years we have tested these products, some years the color lasted the full winter and some years it did not. On average, the best products will have good color for about 75 days.

Products were found to be rate responsive. Applying the colorants (and water carrier) at 160 gpa provided turf color increases up to 44 percent greater than the 80 gpa treatments. Applying colorants at rates above 80 gpa also resulted in increased color longevity over the winter season. As a general rule, as turfgrass height of cut increases, rate of colorant application will also need to increase. Our studies have also shown that when products were applied to semi-dormant turfgrass, the products performed much better due to the greater background color at the time of application. This is a very important point. Some background color goes a long way. Applied to semi-dormant turfgrass, the color will look better and may last longer. For optimum results, do not wait until the turfgrass is straw brown.

In the 2011-2012 and 2012-2013 seasons, 25 products were evaluated (Fig. 1) following a single application. Initial colors were judged to be different among treatments. Four products provided minimal to no color at the time of application. Generally products faded over time, with some products shifting to more of a gray or bluish color. The resulting color rating may be directly related to the initial color or due to the greater deterioration of color over time (Table 1).

A common question is, “what is the best colorant?” In fairness, no one turf colorant was clearly superior in terms of natural green color at the time of application and at the end of the winter season. In our 2011-2012 and 2012-2013 trials, distance matrices grouped colorants based on similarity of attributes such as colorant coverage, colorant quality and hue over a season and years. Distance matrices are a set of statistical procedures that illustrates relationships by grouping items using proximity on a graph using multiple measurements simultaneously. Traditional statistics only show relationships in two variables (e.g., response in y given a change in x.)

Results indicated that the colorants with the best natural green color did not generally last as long as some of the others. This group included Green Lawnger, Lesco Green, Ultradwarf Super, Southwest Green and Endurant. To have a natural green color for the duration of the dormant period, our data suggest reapplication will generally be necessary. A longer-lasting color, although it may have a bluish or lime-green hue, can be achieved with minimum to no reapplication. This group included Kameelyan-Bermudagrass, Kameelyan-Blue, Green Dye Turf Colorant, Go Green, Regreen and Wintergreen. The products not mentioned as part of these two groups generally were statistically lower in the combination of measured attributes.

Price Considerations

Of course, in order for any new practice to be adopted by a superintendent it must make sense financially. Depending on the brand, a gallon of turf colorant will cost from $30 to $75, with most distributors giving volume discounts. This is particularly important if a superintendent wants to apply a product to fairways. Almost all the products are sold as a concentrate that must be further diluted before application. A typical dilution rate is one part colorant to seven parts water, although the suggested dilutions may vary based on product, use, existing turf color and desired result. Some of the more concentrated colorants may be diluted up to one part colorant to 15 parts water. So, carefully read the label to get an idea of how much area one can cover with the product of choice. The cost of colorant needed per acre using the higher recommended application rates would range from $200 to $500 an application, depending on colorant brand.

With seed prices currently a bit higher the last few years, using one of these products could save superintendents a considerable amount of money when compared to overseeding. Considering that overseeding will require ground preparation, seeding, watering, fertilizing, mowing, pest control, spring transitioning, etc.; colorants may be a significant labor saving alternative as well. Although potential monetary savings are a major advantage, the ability to better manage the warm-season grass is what keeps turf managers interested in this practice.

How to Apply/Considerations

The painting process can be boiled down to picking and purchasing a colorant, adding water plus colorant to your sprayer and beginning spraying. Any type of sprayer will work, although a boom-sprayer would be much more efficient. Flat-fan nozzles are commonly used. Air-induction nozzles and dual-fan nozzles are gaining in popularity because they can improve coverage. If the color is not applied evenly or dark enough, additional passes (ideally perpendicular) can be made to accommodate aesthetic desires. There is some clean-up, but no season-long care like with overseeding. Remember to be very careful to not get this product on anything you do not want green. Fences, tee markers, yardage markers, benches, etc. will absorb the colorant and may be permanently stained. These products are not labeled as a pesticide, but you should still use good judgment and wear personal protection equipment when using pressured sprayers.

There are a few other potential drawbacks to using a colorant. It does not provide a wearable surface like an overseeded grass. Once the dormant tissue is worn or torn away, there is no regeneration until spring. So, the “wear factor” must be considered if you get a lot of winter traffic. Also, divot sand in fairways or on tees may stand out more; although most of these products can also be used to color sand.

A common complaint heard is that some of the colorant-treated turf exhibited a bluish tint over time (some quicker than others) (Fig. 2). While this may sound like a negative attribute, in one survey many people did not mind the bluish color. Why blue? Well, often green color is produced by mixing blue and yellow pigments. The yellow pigments are generally not as stable as the blue pigments, so as the products age the blue tends to be the more dominant color. We also found that most of the darker, more bluish products held their color longer than the products that started out a more natural green color. The more natural green products tend to fade to a grayish color as they age. Reapplication can provide improvements for off-colored colorants, but once a product shifts in color, reapplication may not result in a natural green color due to the base color. This is especially true for products that shift to a bluish color. In our research we have not been able to predict color longevity from year to year. The climatic influences on product performance have been a significant factor in this unpredictability.

There are a number of good products on the market, with more being introduced each year. Evaluating colorants has proven to be as challenging as evaluating grass cultivars. Our research has classified the products and shown that they can be an attractive and cost-effective alternative to overseeding. There are still opportunities for improvements to be made in terms of colorant color and longevity.