Germinating and emerging Festuca seedlings between weed seeds. Photos by Daniel Hahn
Turfgrass management is undergoing a significant paradigm shift toward more sustainable practices. This shift affects almost all areas of turfgrass management but influences most notably the use of synthetic herbicides. The limited use or an outright
ban of herbicides necessitates investigating alternative weed-control strategies that ensure both the aesthetic and functional quality of turfgrass areas. In this context, the selection of turfgrass species that can naturally suppress weeds could
become an important aspect of turf management (5).
Fine fescues, specifically within the Festuca genus, are known for their adaptability to low-input conditions, making them candidates for areas in which herbicide use is restricted. The Festuca rubra L. and F. ovina L. complexes comprise various subspecies
(3). These grasses tolerate moderate shade and acidic soils, exhibit drought resistance, and require less water and nutrient inputs compared to some of the other turfgrass species. For instance, Chewings fescue, a species within the complex of F.
rubra, has been identified as suitable for low-input golf course fairways. Similarly, tall fescues adapt well to the climatic conditions of warmer climates, such as southern Europe, making them a good choice for athletic fields in regions like Italy.
The ability of fescues to outcompete weeds was demonstrated in field experiments with 78 fine fescue cultivars from six species. Particularly, cultivars from the red fescue complex (Festuca rubra L.), such as Chewings fescue and strong creeping red fescue
(F. rubra L. ssp. rubra Gaudin), were especially effective in suppressing weeds. The researchers attributed this mainly to quick germination; rapid canopy closure after sowing, which limits light, nutrients and space available to potential weed seedlings;
and potential allelopathic interference (2). The results of these and other investigations indicated that some varieties of Festuca species inhibit the growth of weed species to varying degrees. However, information is lacking about the ability of
Festuca species in their growth interference potential against broadleaf weed species during germination and early growth stages.
Daniel Hahn counting seedlings in germination boxes.
Research was conducted at Wageningen University and Research, the Netherlands, to study differences in germination between Festuca species and varieties and to investigate the influence between and within Festuca species on weed seed germination percentage,
germination speed and root length. For this, we included three weed species: white clover (Trifolium repens L.), lawn daisy (Bellis perennis L.) and yarrow (Achillea millefolium L.). These species are among the most common and most problematic weeds
in European turfgrass areas, making them relevant choices for assessing the weed-suppression potential of the fescue cultivars.
The study included 30 fescue (Festuca spp.) cultivars from three subspecies, including the red fescues and hard fescues from the fine fescue complex, and tall fescues. Selection criteria included species and cultivars commonly used on athletic fields
and golf courses, and availability of seeds. This wide range of cultivars was chosen to provide a diverse basis for assessing the weed-suppression capabilities across different subspecies of fine fescues.
The experiment was conducted twice, first in April 2018 and then replicated in January 2019, to ensure consistency and reliability of the results. In the second round of the experiment, when fresh seeds of certain cultivars were unavailable, leftover
seeds from the first experiment were used. Those had been stored properly to maintain their viability.
The growth medium for the experiment was a purified agar mixture and was chosen for its suitability in supporting both grass and weed seed growth under controlled conditions (1). An appropriate statistical analysis was used to assess all measured variables.
The climate chamber conditions were controlled to simulate suitable growth conditions with published settings for day/night cycles, temperature, humidity and light intensity. Regular rearrangement of the containers within the climate chamber was conducted
to mitigate any potential microclimatic variations and to avoid edge effects that might skew the results.
Figure 1. Final germination percentage (FGP) of 27 Festuca cultivars grown on water agar at 30 days after sowing, grouped according to species (FA, tall fescue; FRR, strong creeping red fescue; FRA, hard fescue; FRC, Chewings fescue; FRT, slender creeping red fescue). Dotted horizontal lines indicate species averages, and solid lines indicate shared cultivar mean separation letters. Means sharing the same letter are not significantly different from one another at the 0.05 probability level according to the Tukey’s HSD test.
Measurements taken during the experiment included Final Germination Percentage (FGP) and Mean Germination Period (MGP) (6) of all grasses and weeds, and total biomass, root and shoot lengths of individual weed plants. Such measurements and analyses allowed
for determining the interactions between the fescue cultivars and the selected weed species, with a particular focus on their germination patterns and growth interference abilities. After the germination period, all containers with lawn daisies had
to be removed from the experiment. In the presence of Festuca species, lawn daisy plants developed poorly and appeared photobleached, and it was not possible to record meaningful data. Consequently, results highlighting lawn daisy are not reported.
Fescue germination and biomass differences
The FGP of species ranged from 93.2% for hard fescue to 86.4% for slender creeping red fescue.
Final germination percentage of strong creeping red fescue (FRR), hard fescue (FRA) and Chewings fescue (FRC) was greater compared to that of slender creeping red fescue (FRT), whereas FGP of tall fescue (FA) did not differ from any of the other species
(Figure 1).
Final germination percentage among cultivars varied from 96.8% (Barcrown, FRT) to 71.1% (Samanta, FRT) (Figure 1). Within all species, except for FRA, which was only represented by two cultivars, FGP of cultivars within species varied.
Mean germination period did not differ among species, but significant differences were observed among individual cultivars. FRR cultivars Livison and Sergei and FRC cultivars Melitta and Ramona germinated faster than Mellori (FRR) and Baroyal and Libano
(both FRT). The study revealed variability in the final germination percentage among the different Festuca species and the cultivars within these species. This indicates a certain range of germination abilities across the fescue spectrum. Interestingly,
the type of weed species present did not significantly influence the FGP of the Festuca species or cultivars, suggesting that their germination effectiveness is more a function of their inherent traits rather than external weed pressure.
Figure 2. Biomass (milligrams/container) of 27 Festuca cultivars grown on water agar for 30 days in a controlled environment, grouped by species (FA, tall fescue; FRR, strong creeping red fescue; FRA, hard fescue, FRC, Chewings fescue; FRT, slender creeping red fescue). Data were averaged over weed species (white clover, Trifolium repens L.; and yarrow, Achillea millefolium L.) and two experiments. Dotted horizontal lines indicate species averages, and solid lines indicate shared cultivar mean separation letters. Means sharing the same letter are not significantly different at the 0.05 probability level according to the Tukey’s HSD test.
Biomass data for Festuca species and cultivars at 30 days after seeding (DAS) was based on observations in containers to which yarrow and white clover were introduced at 13 days after fescue grasses were seeded. Although weed species did not impact Festuca
biomass overall, the species and cultivars within species differed in the amount of developed biomass after 30 DAS. The average biomass weight of FA was higher compared to all other species. Even though FRR was also higher than the other three species,
it produced less than 50% of the biomass of FA. The other three species, FRA, FRC and FRT, had similar biomass (Figure 2).
Impact on weed growth
In terms of the specific impacts on weed growth, the study showed varying degrees of interference by the Festuca grasses. For white clover (Figure 3), [Festuca species and cultivars significantly reduced root length. This indicates a strong suppressive
effect, particularly on root development. The tallest reduction in root length for white clover was observed in the presence of tall fescue, underscoring its potent weed-suppression capabilities. The study also highlighted significant variability
in the weed-suppression capabilities among different Festuca cultivars. This finding is particularly important, as it suggests that the choice of specific cultivars within the Festuca species can significantly influence their effectiveness in weed
suppression. This cultivar-specific variability points to the potential for targeted selection of fescue cultivars based on their specific weed-suppression characteristics.
Figure 3. Root length of white clover (Trifolium repens L.), grown together with 27 Festuca cultivars or as stand-alone control on water agar for 30 days in a controlled environment, grouped by species (FA, tall fescue; FRR, strong creeping red fescue; FRA, hard fescue; FRC, Chewings fescue; FRT, slender creeping red fescue) and experiments. Dotted horizontal lines indicate species averages, and solid lines indicate shared cultivar mean separation letters. Means sharing the same letter are not significantly different at the 0.05 probability level according to the Tukey’s HSD test.
Cultivar-specific suppression effects
For yarrow, although the Festuca species did not significantly affect its FGP or MGP, they substantially reduced its root length. This consistent reduction across all Festuca species and cultivars highlights their general effectiveness in suppressing
yarrow growth, particularly at the root level (Figure 4).
Correlation between biomass and weed suppression
A notable observation from the study was the significant negative association between the biomass of Festuca and the root length of white clover and yarrow, whereas FGP and MGP of white clover had no relationship with Festuca biomass (Table 1). This suggests
a correlation, where larger Festuca plants, potentially due to more robust growth and competitive resource use, are more effective in suppressing weed growth. Such a finding may have implications for understanding the mechanisms of weed suppression
by Festuca species and possible other species and could guide future research and practical applications in turfgrass management.
Interpreting the study's implications
Resource competition and allelopathic interference are two important mechanisms of plant-plant interaction. Allocating the relative effect of each mechanism has been attempted by other researchers, but to date, designing an experiment that convincingly
separates effects of each has proven to be difficult. Since resource competition is prominent under field conditions, determining allelopathic potential is often attempted under laboratory conditions, with minimal supply of nutrients. Because resource
competition cannot be completely excluded even under such experimental conditions, Breuillin-Sessoms et al. (4) proposed to use the term “weed suppression potential.”
In our study, we observed no Festuca species or cultivar effect on germination rate or germination speed. Such a result could possibly indicate that Festuca species only influence weed growth processes but do not affect germination. One could also argue
that the quantity of root exudates reaching the weed seeds was insufficient to influence initial development and growth. If the latter is the case, an alternative to the current experimental design may be needed to more adequately assess the effects
of donor species on the germination of seeds of receiver plants.
Figure 4. Root length of yarrow (Achillea millefolium L.) grown for 30 days on water agar in a controlled environment together with 27 Festuca cultivars or as a stand-alone control, grouped by species (FA, tall fescue; FRR, strong creeping red fescue; FRA, hard fescue; FRC, Chewings fescue; FRT, slender creeping red fescue) and experiments. Dotted horizontal lines indicate species averages, and solid lines indicate shared cultivar mean separation letters. Means sharing the same letter are not different at the 0.05 probability level according to the Tukey’s HSD test.
Our research does shed light on cultivar-specific effects, revealing significant differences in weed-suppression capabilities among the different fescue cultivars. This suggests that for effective weed control, the choice of cultivar is as important as
the choice of species. The negative correlation found between Festuca biomass and the root length of white clover and yarrow adds to the study’s important results. It suggests that larger Festuca plants, possibly because of their more robust
growth and competitive resource use, are more effective in suppressing weed growth. The study’s findings of root growth expressing a more reliable indicator of growth interference than shoot growth coincides with the practical realities of turf
management, where root development and health are known to be critical for overall turf quality and resilience.
This observation is vital for turf managers, as it provides a tangible metric — biomass production — to gauge and select the most effective fescue varieties for weed suppression. It also points to the importance of providing sufficient resources
during establishment for any turfgrass species, and not just Festuca, to stay competitive against weeds. Whether some cultivars may have displayed a higher allelopathic potential, as evidenced by a more robust inhibitory effect on certain weeds, remains
unknown. But a variability among cultivars within the same species underscores the complexities inherent in plant-plant interactions and the importance of cultivar selection in turfgrass management.
Table 1. Spearman's correlation investigating the degree of association between biomass of 27 Festuca cultivars and three white clover (Trifolium repens L.) and yarrow (Achillea millefolium L.) characteristics: full germination percentage (FGP), mean germination period (MGP) and root length.
The research says
- The research sheds light on cultivar-specific effects, revealing significant differences in weed-suppression capabilities among the different fescue cultivars. This suggests that for effective weed control, the choice of cultivar is as important as
the choice of species.
- No Festuca species or cultivar effect on germination rate or germination speed was observed. Such a result could possibly indicate that Festuca species only influence weed growth processes but do not affect germination.
- The study’s findings of root growth expressing a more reliable indicator of growth interference than shoot growth coincides with the practical realities of turf management, where root development and health are known to be critical for overall
turf quality and resilience.
- A variability among cultivars within the same species underscores the complexities inherent in plant-plant interactions and the importance of cultivar selection in turfgrass management.
Acknowledgement
Financial support of this project was provided by the Turfgrass University Research Foundation (TuRF), Nederlandse Golf Federatie (NGF), Nederlandse Vereniging van Golf Accommodaties (NVG) and Nederlandse Greenkeepers Associatie (NGA).
Literature cited
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- Bertin, C., A.F. Senesac, F.S. Rossi, A. DiTommaso and L.A. Weston. 2009. Evaluation of selected fine-leaf fescue cultivars for their turfgrass quality and weed suppressive ability in field settings. Horttechnology 19(3):660-668 (https://doi.org/10.21273/HORTTECH.19.3.660).
- Braun, R.C., A.J. Patton, E. Watkins, P. Koch, N.P. Anderson, S.A. Bonos and L.A. Brilman. 2020. Fine fescues: A review of the species, their improvement, production, establishment, and management. Crop Science 60(3):1142-1187 (https://doi.org/10.1002/csc2.20122).
- Breuillin-Sessoms, F., D.P. Petrella, J.M. Trappe, N.T. Mihelich, A.J. Patton and E. Watkins. 2021. Field evaluation of weed suppression in fine fescue (Festuca spp.). Crop Science 61(4):2812-2826 (https://doi.org/10.1002/csc2.20506).
- Hahn, D., R. Sallenave, C. Pornaro and B. Leinauer. 2020. Managing cool-season turfgrass without herbicides: Optimizing maintenance practices to control weeds. Crop Science 60:2204-2220 (https://doi.org/10.1002/csc2.20175).
- Orchard, T.J. 1977. Estimating the parameters of plant seedling emergence. Seed Science and Technology 5(1):61-69.
Bernd Leinauer (leinauer@nmsu.edu) is a Regents professor and turfgrass Extension specialist at New Mexico State University, Las Cruces, and held the position of endowed chair in turfgrass ecology at Wageningen University and Research, the Netherlands,
for five years; Daniel Hahn is a turfgrass agronomist and scientist based in Munich who graduated from Wageningen University, focusing on herbicide-free management strategies for turfgrass fields in his doctoral thesis; and Lammert Bastiaans is an
associate professor at the Crop and Weed Ecology Group at Wageningen University & Research whose research focuses on the ecology and management of weeds.