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Published online 31 May 2007
Published in Crop Sci 47:1237-1245 (2007)
© 2007 Crop Science Society of America
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TURFGRASS SCIENCE

Stolon Growth and Dry Matter Partitioning Explain Differences in Zoysiagrass Establishment Rates

Aaron J. Pattona,*, Jeffrey J. Volenecb and Zachary J. Reicherb

a Dep. of Horticulture, Univ. of Arkansas, 316 Plant Sci. Bldg., Fayetteville, AR 72701
b Dep. of Agron., Purdue Univ., 915 W. State St., West Lafayette, IN 47907-2054. Purdue Univ. Agriculture Experiment Station Journal 2006-18054

* Corresponding author (ajpatton{at}uark.edu).


   ABSTRACT
TOP
 NOTES
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
A barrier to widespread zoysiagrass (Zoysia spp.) use is its slow establishment rate. Our objectives were to quantify differences in establishment rate of zoysiagrass cultivars and genotypes as well as determine the underlying factors associated with differential growth rates. Thirty-five genotypes of zoysiagrass were transplanted into field plots in June 2004 and 2005. Establishment rate and stolon growth of zoysiagrass genotypes were measured in the field and then four cultivars with contrasting establishment rate were used for further growth analysis in a growth chamber. Mean establishment rate [loge (coverage) d–1] and coverage (cm2) 91 d after planting (DAP) in the field were faster for Z. japonica than Z. matrella genotypes. The Z. japonica Genotype 6186 had the greatest coverage 91 DAP. ‘El Toro’, ‘Chinese Common’, and ‘Palisades’ were among the Z. japonica genotypes that produced more coverage 91 DAP than the mean (1943 cm2), while ‘Meyer’ produced less coverage than the mean. ‘Zorro’ was among the fastest establishing Z. matrella genotypes, and ‘Diamond’ was the slowest. Growth analysis indicated El Toro and Zorro, which establish faster than Meyer and Diamond, partition more dry matter to stolons and rhizomes than leaves. This is consistent with field data where El Toro and Zorro have greater total stolon length than Meyer and Diamond. Zoysiagrass genotypes that partition more dry matter to stems instead of leaves establish the quickest.

Abbreviations: CGR, crop growth rate • DAP, days after plugging • DIA, digital image analysis • LAR, leaf area ratio • LSD, least significant difference • LWR, leaf weight ratio • RGR, relative growth rate • RWR, root weight ratio • SLA, specific leaf area • SWR, stem weight ratio • ULR, unit leaf rate.


   INTRODUCTION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
JAPANESE LAWN GRASS (Zoysia japonica Steud.) and Manilagrass [Z. matrella (L.) Merr.] create a high-quality turf and are used for lawns and golf courses (Beard, 1973). Both species are commonly referred to as zoysiagrass and they are best adapted to the transition, warm–arid, and warm–humid climatic zones of the USA. Zoysiagrass is relatively inexpensive to maintain because of excellent heat, drought, pest, and wear tolerance compared with cool-season grasses (Youngner, 1961; Biran et al., 1981; Reinert and Engelke, 2001; White et al., 2001).

The disadvantages of zoysiagrass are few, but its main disadvantage is slow establishment (Busey and Myers, 1979; McCarty, 2001), which likely limits more widespread use. Researchers have found that methods commonly used to hasten establishment in other turfgrasses including N fertilization and plant growth regulators have little effect on zoysiagrass establishment (Youngner, 1958; Fry and Dernoeden, 1986, 1987; Borden and Campbell, 1987; Dunn, 1991; Richardson and Boyd, 2001). Z. japonica genotypes are reported to have faster establishment rates than Z. matrella genotypes (Forbes and Ferguson, 1947), but there is no published study quantifying differences in establishment rate between species. Genotype selection is also reported to influence establishment rate (Dunn, 1991; Sifers et al., 1992; Hall et al., 1998). Among the most commonly used zoysiagrasses, El Toro and Palisades are among the fastest establishing cultivars, while Meyer and Emerald establish more slowly (Gibeault and Cockerham, 1988; Sifers et al., 1992; Shearman and Morris, 1996; Hall et al., 1998; Morris, 1998, 2004).

Mechanisms influencing differing establishment rates among zoysiagrasses are not understood. Growth analysis is a useful tool for determining causes of differential growth rates. Reviews of these methods are available from Causton and Venus (1981), Hunt (1990, 2003) and Evans (1972). In general, growth analysis uses plant weights and leaf area in formulae to provide a holistic approach to interpret plant performance (Hunt, 2003). Crop growth rate (CGR) is the simplest index of plant growth, but unlike relative growth rate (RGR), CGR does not take into account differences in initial plant size when comparing species (Hunt, 2003). Relative growth rate provides information on plant growth using the natural logarithm of plant weight so that growth rates of different-sized plants may be compared. Additionally, the mean unit leaf rate (ULR) (also referred to as mean net assimilation rate) is a subcomponent of RGR and provides information about the efficiency in which leaves accumulate dry matter. Leaf area ratio (LAR) is a subcomponent of RGR and provides information on the amount of biomass that is partitioned into leaf area. Additionally, specific leaf area (SLA) describes leaf area per leaf weight and ratios such as leaf weight ratio (LWR), stem weight ratio (SWR) and root weight ratio (RWR) describe how a plant partitions its dry matter into various plant parts.

Numerous growth analyses have generally found that grasses with higher RGR values have higher SLA (Poorter and Remkes, 1990; Garnier, 1992; Atkin and Lambers, 1998), which is similar to findings in dicots (Dijkstra and Lambers, 1989; Poorter and De Jong, 1999). Grass species with high RGR are also known to have higher ULR (Garnier, 1992) and higher LWR and LAR (Poorter and Remkes, 1990). The objectives of our research were to determine differences in establishment rate of zoysiagrass cultivars and genotypes, and to determine the underlying factors associated with differential growth rates among zoysiagrasses.


   MATERIALS AND METHODS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 REFERENCES
 
Establishment Rate
Plant material of commercially available cultivars and genotypes of zoysiagrass (Table 1) were collected in fall 2003 and propagated in the greenhouse (23 ± 5°C) in plug trays with 8- by 8- by 8-cm divisions filled with fritted clay (Turface, Profile Products LLC, Buffalo Grove, IL). Vegetatively established genotypes were planted into trays as plugs or stolons and seeded genotypes were seeded (49 kg ha–1) into trays. Plants in the greenhouse were fertilized monthly with 49 kg ha–1 N, 21 kg ha–1 P, and 40 kg ha–1 K using a soluble fertilizer (18N–7.9P–17.4K) and mowed weekly at 4.0 cm. Plants were transplanted into field plots at the W.H. Daniel Turfgrass Research and Diagnostic Center, West Lafayette, IN. Experimental plots were 1.0 by 1.0 m arranged in a randomized complete-block design with four replications. One vegetative plug (8 by 8 by 8 cm) of zoysiagrass was transplanted into the center of each plot for both seeded and vegetative genotypes on 7 June 2004 and 2005 and irrigated four times daily for the first month to encourage establishment and then irrigated as needed to prevent wilting. Soil type was a Stark silt loam (fine-silty mixed mesic Aeric Ochraqualf) with a pH of 7.0, 224 kg ha–1 P, 808 kg ha–1 K, and 84 g kg–1 organic matter in 2004; and with a pH of 6.8, 224 kg ha–1 P, 639 kg ha–1 K, and 29 g kg–1 organic matter in 2005. The areas were fumigated with methyl bromide at 732 kg ha–1 before establishment each year to minimize weed competition. Plots received 49 kg ha–1 N from urea (46N–0P–0K) on 1 July and 1 August of each year and weeds were manually removed during establishment.


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  		Table 1. Zoysiagrass (Zoysia spp.) cultivar/genotype, species, typical type of establishment method and source of plant material.

 

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  		Table 3. Zoysiagrass (Zoysia spp.) coverage, establishment rate, stolon length and stolon growth rate by cultivar/genotype, data were averaged over 2004 and 2005.

 
Digital images of each plot were taken weekly with a Nikon Coolpix 3200 (Nikon, Melville, NY) digital camera mounted on a monopod to ensure a consistent height from the lens to the soil surface (1.05 m). Coverage of zoysiagrass was determined using digital image analysis (DIA) (SigmaScan Pro, Systat Software, Richmond, CA) (Richardson et al., 2001). To selectively identify green leaves in the images, the hue range was set from 47 to 107 and the saturation was set from 10 to 100. Richardson et al. (2001) analyzed images with the saturation set from 0 to 100. However, when images taken on our soil with our camera were analyzed with saturation set at 0 to 100, scanning software would overestimate coverage by selecting some of the surrounding soil. To increase accuracy, the lower limit of saturation was raised to 10. Images were taken of a calibration disk and data converted from selected green pixels to zoysiagrass coverage (cm2).

Using a sod staple, stolons and detectable rhizomes reaching the plot border were angled back into the plot to prevent encroachment into adjacent plots and to ensure that all growth from the plug was measured using DIA. Plots were not mown because of the use of sod staples and to avoid genotype by mowing interactions since Zoysia spp. have different optimum mowing heights (Higgins, 1998; Unruh et al., 2000).

A weather station onsite monitored daily air temperature (Fig. 1). The start of winter dormancy (leaf discoloration) occurred 112 and 113 d after plugging (DAP) in 2004 and 2005, respectively, but final coverage is reported only until 91 DAP because establishment rate decreased with decreasing temperatures in autumn and because some genotypes approached complete plot coverage. To determine an establishment rate for each genotype, coverage was transformed using the natural logarithm so the data could be fit to the linear model [Coverage = (KxDAP) + I], where K is the rate of increase (establishment rate, loge coverage d–1), DAP is days after plugging, and I was equal to the natural logarithm of 64 cm2, which was the starting coverage for all plots.


Figure 1
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  		Figure 1. Maximum and minimum daily temperatures and monthly rainfall during 2004 and 2005.

 
At 43 DAP, the length of individual stolons was measured from the edge of the original plug to the tip of the stolon. Additionally, stolon growth was measured over a 7-d interval by marking the growing tip of three stolons in each plot with toothpicks and measuring elongation with a Vernier caliper 7-d later. Stolon growth rate measurements were collected from 57 to 71 DAP in each year of the study and stolon growth rate (mm d–1) determined. Rhizomes were not measured in our study because only nondestructive measurement techniques were used to preserve plots for future measurements of coverage and winter survival. Last, leaf blade width was also measured with a Vernier caliper 64 DAP.

Data were analyzed using PROC ANOVA, PROC TTEST, and PROC REG (SAS Institute, Cary, NC). Error variances were homogenous for dependent variables and thus data were combined across years. When differences were examined between species, ‘J-14’ (Z. sinica Hance) was grouped with Z. japonica and Emerald (Z. japonica x. Z. pacifica Goudsw.) was grouped with Z. matrella because of their similarities in color, texture, and density with respective species. Means were separated using Fisher's protected least significant difference (LSD) when F tests were significant at {alpha} = 0.05.

Growth Analysis
Based on preliminary results from the field study, one slow-growing and one fast-growing cultivar of both Z. japonica and Z. matrella were selected for further growth analysis. Z. japonica cultivars El Toro (fast-growing) and Meyer (slow-growing) and Z. matrella cultivars Zorro (fast-growing) and Diamond (slow-growing) were selected for these experiments. Cultivars were planted in silica sand-filled 2.5-cm diam. Ray Leach cone-tainers (Stuewe & Sons, Corvallis, OR) using a 1- to 2-cm segment of stolon or rhizome containing a single node and leaf and root tissues. Plants were fertilized daily after planting with half-strength Hoagland's solution (Epstein and Bloom, 2005). Plants were established in the greenhouse for 6 wk (26 July–6 Sept. 2004, and 20 June–1 Aug. 2005) at 24 ± 6°C. Plants were then transferred to a growth chamber (PGR15, Controlled Environments, Pembina, ND) maintained at 30 ± 0.7°C with 70% relative humidity and 14-h photoperiod of 816 µmol m–2 s–1 photosynthetically active radiation.

Eight whole plants of each cultivar were harvested when plants were transferred to the growth chamber and once per week for the next 5 wk for a total of six harvests. Leaf blades, roots and the remaining fraction that consisted of mainly leaf sheaths, rhizomes and stolons were separated. This third fraction containing leaf sheaths, rhizomes and stolons will be termed "stem". Leaf area was determined using DIA (SigmaScan Pro Version 5.0, Systat Software, Richmond, CA) (Richardson et al., 2001). Leaves were placed on black fabric after harvesting and covered with nonreflective glass. Digital images (Nikon Coolpix 3200, Nikon, Melville, NY) of leaves were taken immediately after harvest from a set height (33 cm), processed to remove background effects (Adobe Photoshop 6.0, Adobe Systems, San Jose, CA) and DIA was used to determine the number of green pixels per image. To selectively identify green leaves in images, the hue range was set from 47 to 107 and the saturation from 0 to 100. Images were taken of a calibration disk and the data converted from selected green pixels to leaf area (cm2). Root and stem tissues were washed with water to remove the majority of silica sand and then all tissues were dried separately (at least 72 h at 60°C) and weighed. Root weights were calculated as the difference in dry weight before and after combustion in a muffle furnace (at least 3 h at 600°C) to account for silica sand remaining after washing.

Growth analysis values were calculated using formulae in Table 2 and values were then verified using the spreadsheet tool provided by Hunt et al. (2002) that calculates classical growth analysis values. This experiment was conducted in 2004 and repeated in 2005. Error variances were homogenous for dependent variables and data were combined across years. Data were analyzed using PROC MIXED (SAS Institute, Cary, NC). Mean RGR and other growth components were separated using Tukey's test for significant differences when F tests were significant at {alpha} = 0.05.


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  		Table 2. Growth analysis abbreviations, meanings, units, formulae, symbols and quantities used for Zoysia spp. growth rate analysis.

 

   RESULTS AND DISCUSSION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
REFERENCES
 
Establishment Rate
We observed differences (p < 0.0001) in coverage among 35 different zoysiagrass genotypes 59 and 91 DAP (Table 3). Differences in coverage among genotypes were minimal before 59 DAP and thus data is not shown. Coverage ranged from 184 to 959 cm2 59 DAP, and 425 to 4142 cm2 91 DAP. Genotypes 6186, DALZ0102, El Toro, PZB 33, ‘Chinese Common’, 6136, ‘Companion’, and BMZ 230 had coverage 59 DAP that was significantly greater than the mean value of 524 cm2. With the exception of Companion, these genotypes along with Palisades also had the greatest coverage 91 DAP compared with the mean of 1943 cm2. Meyer is considered an industry standard because it is widely used by turfgrass practitioners and researchers and has been available since the 1950s. Meyer produced significantly less coverage 91 DAP (1203 cm2) than the mean. Fourteen genotypes had greater coverage than Meyer 59 DAP, whereas Diamond was the only genotype with significantly lower coverage than Meyer 59 DAP.

Scatter plots of zoysiagrass coverage vs. days after planting revealed a nonlinear relationship. After a natural logarithm transformation, establishment rate was determined by linear regression with r2 values ranging from 0.91 to 0.99. Establishment rate [K, loge (coverage) d–1] ranged from 0.0191 to 0.0448 for Diamond and 6186, respectively, with a mean of 0.0338. Genotypes 6186, DALZ0102, El Toro, PZB 33, Chinese Common, 6136, Companion, and BMZ 230 had establishment rates significantly greater than the mean value of 0.0338 loge (coverage) d–1. Meyer had an establishment rate similar to the mean [0.0307 loge (coverage) d–1]. El Toro, Companion, and Palisades had the highest establishment rates among commercially available Z. japonica cultivars. Genotypes Zorro, DALZ0104, and DALZ0101 had the highest establishment rates among Z. matrella.

We observed differences (p < 0.001) in mean stolon length, total stolon length and stolon growth rate among 35 different zoysiagrass genotypes (Table 3). Mean total stolon length 43 DAP ranged from 2.6 to 26.2 cm, total stolon length 43 DAP ranged from 11 to 365 cm and stolon growth rate ranged from 1.7 to 11.3 mm d–1. Diamond and 6186 were the lowest and highest, respectively, for all stolon growth parameters measured. DALZ0102, 6186, PZB 33, Chinese Common, 6136, and BMZ 230 had the highest mean stolon lengths 43 DAP, which were greater than the mean value of 11.1 cm. These genotypes along with Companion also had the greatest total stolon length 43 DAP, compared with the mean of all genotypes (145 cm). Stolon growth rate was greater than the mean (6.6 mm d–1) for 6186, El Toro, Chinese Common, BMZ 230, Palisades, and J-37. Stolon length for Meyer was similar to the mean, but total stolon length for Meyer was less than the mean. Stolon growth rate for Meyer (5.0 mm d–1) was similar to the mean and consistent with an earlier report of 4.9 mm d–1 (Daniel, 1955). El Toro, also widely used by practitioners and known for its quick establishment rate had a stolon growth rate (9.2 mm d–1) that was among the highest of all genotypes. In general, genotypes with high coverage and establishment rates had the highest stolon growth rates and longest stolons.

Similar to an earlier report (Forbes and Ferguson, 1947), Z. japonica genotypes in our study produced more coverage and had a higher establishment rate than Z. matrella genotypes (Table 4). Z. japonica has wider leaves (2–4 mm) than Z. matrella (<2 mm) (Anderson, 2000). Leaf width across species was positively correlated with establishment rate (r2 = 0.33, p = 0.0003), with wide-bladed genotypes having the fastest establishment rate (Fig. 2a). However, interspecific analysis shows that leaf width within species does not significantly influence establishment rate (Fig. 2b, 2c). Therefore, the relationship between leaf width and establishment rate across species indicates that species (genetics) is the most likely cause for differences in establishment rate and not leaf width.


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  		Table 4. Influence of species and establishment type on zoysiagrass (Zoysia spp.) coverage 91 d after plugging (DAP) and establishment rate. Data were averaged over type, species and years.

 

Figure 2
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  		Figure 2. Relationship between leaf width and establishment rate for (A) both species, (B) Zoysia japonica Steud., and (C) Zoysia matrella (L.) Merr. Establishment rate was determined by fitting coverage data across time to the model [loge (Coverage) = (K*DAP) + loge (64)], where K is the rate of increase (establishment rate). Significant at p < 0.001 level (***) or not significant (NS).

 
Z. japonica is sold commercially both as seed or vegetative propagules, but Z. matrella is only available as vegetative propagules. All genotypes were established by vegetative plugs for our field study, and it was found that genotypes with seed availability had an establishment rate similar to cultivars available only as vegetative propagules (Table 4). This is similar to Karcher et al. (2005) who found that divot recovery of a 2-yr-old stand of zoysiagrass was comparable between cultivars established either by seed or vegetative propagules. However, Karcher et al. (2005) also reported seeded cultivars recovered slower than vegetative cultivars during the 1st year, primarily because seeded cultivars had not yet developed as many rhizomes and stolons as vegetative cultivars. All genotypes were established by 8-mo-old vegetative plugs instead of by seed in our study, which may account for why we did not see differences between genotypes with seed availability and those available only as vegetative propagules.

The slow growth of zoysiagrass is possibly its greatest disadvantage, especially compared with bermudagrass that is also adapted to parts of the transition zone (Cynodon spp. Rich.) (Busey and Myers, 1979). El Toro is described as the fastest-establishing zoysiagrass cultivar (Gibeault and Cockerham, 1988; Sifers et al., 1992; Shearman and Morris, 1996; Morris, 1998) whereas traditional cultivars like Meyer and Emerald establish slowly (Sifers et al., 1992; Shearman and Morris, 1996; Hall et al., 1998; Morris, 1998, 2004). There is a need to develop zoysiagrass cultivars with faster establishment rates because of its slow growth (Engelke and Anderson, 2003). In our study, genotypes such as 6186, DALZ0102, and PZB 33 had a similar establishment rate to El Toro. Palisades, a newly released cultivar (Engelke et al., 2002b), had similar establishment rate and coverage 91 DAP to El Toro. Additionally, 6186 coverage 91 DAP was greater than El Toro. These results indicate that newer genotypes exist with rapid establishment rates.

Though there are few reports comparing establishment among Z. matrella cultivars because of their relatively recent release, we found that the newly released Z. matrella cultivar Zorro (Engelke and Reinert, 2002) has a greater establishment rate and higher coverage 91 DAP than the older cultivar Emerald (Z. japonica x. Z. pacifica Goudsw.), which is similar in color, texture, and density to Z. matrella (McCarty, 2001). Planting newer cultivars with improved establishment rates could dramatically reduce time, inconvenience, and cost of establishing zoysiagrass.

Plots were not mown in this study, but preliminary evidence from a similar field study in 2006 with five cultivars indicates that mowing at 3.2 cm reduces establishment rate compared with unmown plots (Patton and Reicher, 2006). Although low mowing heights decreased establishment rate, it did not change the relative rankings of cultivars and there were no mowing height x cultivar interactions (Patton and Reicher, 2006). Hall et al. (1998) established six zoysiagrass cultivars by either sprigging or plugging, and found that sprigging generally resulted in faster establishment than plugging, but that planting method did not change the relative establishment rankings of cultivars. Additionally, Karcher et al. (2005) recently examined divot injury recovery among vegetatively propagated zoysiagrass cultivars and found that establishment rate was closely related to recuperative potential. Therefore, our establishment rate results (rankings) should be applicable for approximating the establishment rate by either sprigs or recuperative potential from stolons after injury. However, our study results best describe establishment from stolons and potential recovery from stolons since rhizome growth was not measured. Therefore, the recovery of cultivars that produce more rhizomes than stolons, such as Diamond (Engelke et al., 2002a), may be underestimated by our study.

Growth Analysis
Analysis of variance indicated differences between the four cultivars for all growth analysis parameters. Trends in CGR among cultivars closely followed trends in establishment rate and coverage 91 DAP in the field study. El Toro had the highest CGR and Diamond the lowest (Table 5). The CGR of Diamond is low because individual plants are small and initial mass is not accounted for by CGR. When plant weights are transformed with the natural logarithm allowing for a more equitable comparison, the resulting RGR values indicate that Diamond has the greatest growth efficiency and that El Toro, Zorro, and Meyer all have similar RGR values. Unlike previous reports with other plants (Poorter and Remkes, 1990; Garnier, 1992; Atkin and Lambers, 1998), there were no significant correlations between RGR with any of the other growth components (ULR, LAR, SLA, LWR, SWR, and RWR) (Table 5), which may be expected because only Diamond had a significantly higher RGR than the other three cultivars.


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  		Table 5. Growth analysis mean values of zoysiagrass (Zoysia spp.) cultivars grown in a growth chamber maintained at 30°C with 70% relative humidity and 14-h photoperiod of 816 µmol m–2 s–1 photosynthetically active radiation. Correlation coefficients between mean relative growth rate and other growth components were calculated and their significances are given at the bottom of the table.

 
Dry matter production by leaves was most efficient (ULR) for Diamond (23.6 g m–2 d–1) and Zorro (22.1 g m–2 d–1), followed by El Toro (17.3 g m–2 d–1) and Meyer (12.6 g m–2 d–1). High ULR of Diamond and Zorro were likely due to their narrow leaves compared with Meyer and El Toro. Narrow leaves decrease shading of other leaves and allow for greater production efficiency. Despite Diamond and Zorro having similar ULR values, dry weight was partitioned differently. On a relative basis, Diamond partitions 2.8%, and 4.6% more dry weight into leaves (LWR) and roots (RWR), respectively, than Zorro. By comparison, Zorro invests more (7.4%) of its dry weight into stolon and rhizome (SWR) mass than Diamond. This difference in dry matter partitioning may explain why Zorro established more quickly in the field than Diamond. El Toro and Meyer also have similar ULR values, but partition dry weight differently among plant parts. El Toro partitioned 1.6 and 3.6% more dry weight to produce roots (RWR) and stolons and rhizomes (SWR), respectively, than Meyer. Meyer, however, partitioned more dry weight (5.2%) to leaves (LWR) than El Toro.

Within species, cultivars with lower CGR such as Diamond and Meyer have higher LAR and SLA values. More dry matter was partitioned into leaf area (LAR) and for Meyer (7.1 m2 g–1) than Diamond (5.8 m2 g–1), El Toro (4.9 m2 g–1) and Zorro (4.1 m2 g–1). Similarly, SLA was greatest for Meyer (23.8 m2 g–1) followed by Diamond (21.5 m2 g–1), El Toro (19.7 m2 g–1) and Zorro (16.7 m2 g–1). Higher LAR and SLA values for Meyer and Diamond indicate that these cultivars are more leafy and that the individual leaves were thinner than El Toro and Zorro. Differences in SLA of certain grasses is attributed to higher mineral and organic N compounds, (hemi)cellulose or lignin content (Van Arendonk and Poorter, 1994). Tissues were not analyzed for differences in chemical or physical composition in our study, so it is unclear what caused differences in SLA.

Overall, growth analysis data suggest genotypes that establish quickly produce a greater proportion of stems (stolons and rhizomes) than leaves compared with slow-establishing genotypes. This is consistent with our field data where genotypes with high establishment rates had longer stolons (Table 3). For instance, Meyer and Diamond partition more dry matter into leaf area than stems, which is likely why they establish and spread slowly in the field. However, Diamond is reported to have vigorous rhizomatous growth (Engelke et al., 2002a). Future work should examine differences in dry matter partitioning between rhizomes and stolons of genotypes with varying establishment rates.

There are considerable differences in zoysiagrass growth and establishment rates between species and genotypes. Z. japonica genotypes generally have higher establishment rates than Z. matrella genotypes. Genotypes capable of producing long stolons with high growth rates establish quickly. High stolon growth rate of quick-establishing genotypes is due to a higher proportion of dry weight partitioned to stems instead of leaves. Therefore, breeders could develop cultivars with faster establishment rates by selecting plants that partition more dry matter to stems. Genotypes we tested established as fast or faster than the best-establishing commercially available cultivars. Bermudagrass has a faster establishment and recovery rate than zoysiagrasses (Busey and Myers, 1979), which sometimes precludes zoysiagrass from being used for turf. However, identification of newer cultivars with quicker establishment and recovery than the industry standards of Meyer may make selecting zoysiagrass a more acceptable option to bermudagrass. Practitioners should select available zoysiagrass cultivars with fast establishment and recovery rates to help reduce establishment time, increase revenue and improve course conditions.


   ACKNOWLEDGMENTS
 
This research was supported by the Midwest Regional Turfgrass Foundation and the Tri-State Superintendents Association. Special thanks to Daniel Weisenberger for his help harvesting zoysiagrass plants and for reviewing this manuscript.


   NOTES
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 NOTES
ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
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Received for publication October 3, 2006.


   REFERENCES
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 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 




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A. J. Patton and Z. J. Reicher
Zoysiagrass Species and Genotypes Differ in Their Winter Injury and Freeze Tolerance
Crop Sci., July 30, 2007; 47(4): 1619 - 1627.
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