Tiller demography in tall fescue (Festuca arundinacea) swards as influenced by nitrogen fertilization,sowing method and grazing management

Tall fescue is an important temperate grassland species globally, but in many regions the effects of drought, heat and poor grazing management, reduce its persistence in summer. Furthermore, poor ground cover and low tiller population density (TP) in winter result in low radiation capture and thus limited potential to increase the low growth rates at that time. Knowledge of the effect of fertilization, defoliation managements and establishment methods on demography of tall fescue would help to improve sward management for better persistence and winter growth. Accordingly, an experiment was carried out in Pergamino, Argentina, to study the effects of two N‐ fertilizer levels, two grazing frequencies and two seeding row arrangements upon tall fescue TP demography. Herbage mass, tiller appearance (TA) and death rates were measured over 3 years. Seasonal fluctuations in TA and death rates determined well‐defined periods of increase and decrease in TP density. Maximum values were found at the end of winter and minimum ones at the end of spring, after the reproductive period. Nitrogen shortage and high herbage mass limited TA. Tiller death rate followed TA rate and was affected by nitrogen supply and defoliation frequency in the same way that TA was. Sowing arrangement affected tiller demography at the beginning of the experiment.     

Reproductive tillers in cut tall fescue swards: differences according to sward age and fertilizer nitrogen application, and relationships with the local dynamics of the sward

The effects of sward age and fertilizer‐nitrogen (N) application rate on reproductive tillers and their involvement in the dynamics of swards of perennial grasses were investigated using sown swards of tall fescue (Festuca arundinacea). Treatments included plots representing two sward ages (two and six‐year‐old swards) and two fertilizer‐N rates (150 and 350 kg N ha^?1 yr^?1) on the same experimental field. In each of 2 years all plots were cut at the silage stage and three times afterwards. After each cut, during two growing seasons, the vegetative tillers and stubs of cut reproductive tillers were counted in ten permanent quadrats for each of the four treatments, using a grid of 150 cells, each of 2 cm × 2 cm. The results showed a higher density, and a greater proportion of reproductive tillers, on the higher fertilizer‐N rate treatment and on the older swards. The density of vegetative tillers was found to be greater in close proximity to the reproductive tillers in all sward treatments and in both assessment years. Thus, cutting the reproductive tillers did not result in thinning of the swards. It is suggested that a mother‐tiller effect, enhancing renewal of tillers, was likely, although zones bearing reproductive tillers during the second spring were sometimes already denser than zones in the rest of the quadrats before the winter.     

Effect of heading date of perennial ryegrass cultivars on tillering and tiller development in spring and summer

Three cultivars (two diploid and one tetraploid) in each of three maturity groups (early, intermediate and late) of perennial ryegrass were sown in 10 m² plots, replicated four times, in Northern Ireland in June 1997 in a study of the effect of heading date on tiller development (including initiation to flower) and turnover of tillers produced at specific times in spring in 1998 and 1999. The plots were harvested seven times in each year. Annual dry‐matter production was similar for all groups in each year. In spring and early summer of both years, tiller density of the diploid cultivars was 1·5 times greater than that of the tetraploid cultivars and the mean tiller density over all swards in June was about 0·40 times greater than that in April. Maximum proportions of reproductive tillers in the early, intermediate and late maturity groups, determined from apical dissections, were found in early April, mid‐May and early June, respectively. Although a high proportion of tillers, which were present when annual observations commenced in spring, was decapitated at the first harvest in the early group, the previous population density was maintained by rapid production of new tillers during May, including those from suppressed tiller buds during reproduction. It is concluded that the relationship between heading date and rate of tiller turnover (including flowering) at specified times in spring is important in sward management throughout the early part of the growing season and should be taken into account in tiller‐based grass growth models.     

Sowing date and nitrogen supply determine the outcome of competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the Pampas region of Argentina

The effects of sowing date and nitrogen (N) fertilizer on the inter‐specific competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the humid Pampas of Argentina were investigated in two pot experiments where a constant soil moisture content was maintained. Tall fescue and dallisgrass seeds were sown either in the spring (October 2000) or in the autumn (March 2001) in mixed and mono‐specific stands with 0 or 100 kg N ha^?1. In the spring, competition from tall fescue depressed dry‐matter (DM) yield of dallisgrass from 1·53 to 0·36 g DM per plant and tiller number from 9·4 to 3·7 tillers per plant in mixed and in mono‐specific stands, respectively, while tall fescue had 3–4 times higher DM yields in mixed stands. Leaf extension rate (LER) of tall fescue was higher (1·3 mm d^?1) than that of dallisgrass (0·53 mm d^?1). In the autumn, inter‐specific competition did not affect DM yield of dallisgrass and N fertilizer increased DM yield from 0·53 to 2·07 g DM per plant, tiller number from 6·8 to 14·2 tillers per plant and LER at the beginning of autumn from 1·2 to 2·12 mm d^?1 in both species. As temperature decreased, LER was reduced in both species to 0·31 mm d^?1 by late autumn. The number of leaves per tiller was not affected by treatment. Nitrogen fertilizer increased N concentration of above‐ground tissues of both species (18 g kg^?1 DM in autumn and 20 g kg^?1 DM in spring). It was concluded that a productive mixed pasture of dallisgrass and tall fescue can be obtained by sowing early in the autumn. The application of N fertilizer in this season is essential to ensure a high herbage yield and quality.     

The relationship between tiller appearance in spring and contribution to dry-matter yield in perennial ryegrass (Lolium perenne L.) cultivars differing in heading date

The relative contribution of tillers present in April and those appearing in consecutive periods in spring was assessed for perennial ryegrass cultivars in the three maturity groups (early, intermediate‐ and late‐heading). Each group was represented by two diploid and one tetraploid cultivar each in plots in their third (2000) and fourth (2001) harvest years in three replicated blocks receiving an average of 325 kg N ha^?1 and cut seven (in 2001) or eight (in 2000) times annually. ‘Main’ tillers and their daughters were marked with colour‐coded PVC‐covered wire loops in early April as were daughters which appeared in consecutive periods between harvests, the loop colour identifying the period of origin of the tiller. Tillers were harvested at cutting height (5 cm) before the plots were harvested and the herbage from tillers with the same colour code bulked per plot. Tillers were identified retrospectively as ‘reproductive’ if they had been decapitated at the previous harvest. Dry‐matter yield was higher in the early than late‐heading cultivars in April and early May but this was reversed in harvests in late May and June. The early heading group had a lower lamina content than the late‐heading group during reproduction growth, both due to the reproductive tillers (mainly those which overwintered) having a lower leaf content and to their being fewer and smaller vegetative tillers during the reproductive phase than for the late‐heading group. Turnover of tillers was high in spring due to decapitation of reproductive tillers and rapid post‐flowering tillering. This was particularly pronounced in the early heading group which also had slightly more tillers marked in April which were subsequently decapitated than in the other maturity groups, i.e. 0·56 compared with 0·44 for the late‐maturing group. Mean ratios of rate of death: rate of tillering for 3 years (1999–2001) for the early and late‐heading groups were 0·8 and 0·4, respectively, for April–May and 1·1 and 2·4, respectively, for June indicating the different patterns in tiller turnover for the two extreme maturity groups. Information on tiller origin and contribution to yield can be used to refine tiller‐based grass growth models.     

Canopy structure and productivity of Festuca avundinacea Schreb. swards during vegetative and reproductive growth

Canopy structure, productivity and their relationships were examined in 2-year-old swards of fourteen tall fescue ( Festuca arundinacea Schreb.) strains during the vegetative and reproductive growth stages. During the vegetative growth stage morphological characters, particularly tiller size, were closely associated with productivity. Swards with large tillers showed an effective distribution of the incoming light energy within the canopy and hence low extinction coefficient ( K ) value and high productivity at complete light interception. On the other hand, although there was no apparent correlation between K and the productivity or the whole crop during the reproductive growth stage, the productivities of the reproductive and vegetative tillers were positively and negatively related to K respectively. Leaf area index of the reproductive tillers and their position in the canopy had marked effects on the distribution of the incoming light energy within the canopy and on the productivity of both types of tillers. The productivity of the vegetative and the reproductive tillers is discussed in terms of the effect of the competition for incoming light energy between both types of tillers.     

FERTILE TILLER PRODUCTION AND SEED YIELD IN MEADOW FESCUE (FESTUCA PRATENSIS L.)

The fertile tiller production and seed yields of spaced plants of meadow fescue varieties were found to vary widely with the time of sowing, particularly in the first harvest year. The benefit of early spring sowing is indicated in the total productivity over two harvest years.
Varieties differed in the amount of heading in the seeding year; the American type was the most prolific. This had a bearing on the relative yields in the first harvest year, since many of the potentially productive tillers of this variety were wasted through the plants becoming ripe to flower in the seeding year and, therefore, the rate of tiller production was checked. Competition within the plant appeared to be the cause of tillers remaining vegetative when conditions otherwise seemed suitable for generative development. The smaller-sized plants gave a higher proportional increase of fertile tillers at harvest than would be expected from the vegetative tillers counted in April, while at the same time there was a negative relationship at harvest from plants which had a very high number of vegetative tillers.
Infertility as reflected in a poor seed set at the time of harvest is a serious wastage of potential production in meadow fescue and, in selecting for superior seed output, breeders need to take this factor into consideration.
The 1000-seed weight varied between varieties, the pasture type being inferior to the two hay types.     

Water use efficiency and drought survival in Mediterranean perennial forage grasses

In Mediterranean areas, water use efficiency (WUE) is mainly increased by maximising crop growth during the rainy seasons. Perennial forage species have a number of advantages in comparison to the predominantly used annuals. They can utilize water from autumn to spring, while annuals need to be sown or to germinate from the soil seed bank. Under Mediterranean annual rainfall pattern, perennial plants must grow from autumn to spring and survive under summer aridity. Drought survival can impact water use efficiency through plant mortality and stand recovery after autumn rainfalls. In order to enhance knowledge of physiological and agronomic traits associated with WUE and persistence, a 3-year study was conducted at two Mediterranean sites, comparing a range of accessions of two perennial species, cocksfoot (Dactylis glomerata L.) and tall fescue (Lolium arundinaceum (Schreb.) Darbysh). Within the accessions of predominantly Mediterranean origin, we defined four major functional types, i.e. groups of accessions with similar response to summer drought. One type (FT1) is represented by the only cultivar of a semi-arid cocksfoot (Kasbah) that is completely summer dormant, with high persistence under the most arid situations but with low WUE. The type FT2 all cocksfoot cultivars (Currie, Delta-1, Jana, Medly, and Ottava) that are not or less summer dormant, with good perenniality and intermediate productivity at rainy seasons. The type FT3 includes the cultivars of tall fescue (Centurion, Flecha, Fraydo, and Tanit) that combine an incomplete summer dormancy, a deep rooting system and the highest WUE from autumn to spring. The type FT4 is represented by a cultivar of tall fescue (Sisa) with no summer dormancy, therefore less persistent and also less productive. Dehydration avoidance in tall fescue and cocksfoot and summer dormancy in cocksfoot were the main strategies contributing to persistence under summer drought. WUE in autumn was highly correlated with sward recovery after drought. Seasonal and total WUE were also highly correlated with biomass production over the same period and with depth and density of the root system. Parameterization of functional types of the major species of forage grasses will enhance future modelling work to test the effects of a range of environments and future climate scenarios.     

SOME EFFECTS OF GRAZING MANAGEMENT ON THE YIELD AND ITS COMPONENTS OF SOME PASTURE GRASSES

A study was made to determine the effects of grazing to a height of 1 in. when the swards reached heights of 3 and 9 in. on the dry matter production, LAI, tillering and rate of leaf production of new and old tillers in the spring–summer and autumn–winter seasons of 3 pasture species growing in association with white and red clovers. In both seasons the herbage yield under 9–1 management was higher than that under 3–1 and was significantly greater in the spring-summer season. Differences in DM production between cocksfoot, tall fescue and Ariki ryegrass failed to reach significance.
Light utilization under the 2 management systems was considered to be inefficient. In the autumn-winter period there was a linear relationship between the LAI and DM production in all treatments.
The rate of leaf production per tiller was significantly higher in cocksfoot than in ryegrass and tall fescue in both seasons.
New tillers had a significantly higher rate of leaf production than old tillers in the spring-summer period, but not in autumn-winter. The numbers of grass tillers and rooted nodes of clover were significantly higher under 3–1 than under 9–1 and were influenced by season.     

Tillering and leaf area index in grasses in the vegetative phase

The relationship between tillering of a vegetative grass stand and Leaf Area Index (LAI) has been studied during sward establishment of perennial ryegrass and Italian ryegrass with different seedling densities and nitrogen fertilizer rates and on established swards of tall fescue during winter and early spring after different dates of last cut in autumn.
The different experiments on different species led to the conclusion that in every instance the tillering rate slows down as soon as the LAI reaches a value of 3 and terminates rapidly at higher LAI, which corresponds with the almost complete extinction of light at the level of the tiller buds. The results confirm the direct role of light on morphogenesis previously demonstrated by several authors. The existence of such a limit of LAI helps to explain some contradictory effects of temperature or nitrogen on tillering.     

Soil moisture and growth of contrasting varieties of Lolium, Dactylis and Festuca species

Varieties of Italian, perennial and Italian × perennial ryegrasses, tall fescue and cocksfoot were used to determine the effects of soil moisture on grass growth. Weather conditions were monitored and herbage accumulation, leaf extension rate, leaf appearance rate and tillering were recorded under natural (control), covered and irrigated treatments.
Water deficit reduced crop growth rate in the spring and drought was the major factor influencing crop growth rates in all varieties during the summer. The ryegrasses appeared most sensitive to drought, and particularly poor recovery growth was exhibited by the Italian ryegrass RvP and the hybrid ryegrass Snowdon.
Leaf extension rate and leaf appearance rate were both reduced by increasing soil water deficit. Herbage accumulation was increased by irrigation when potential soil water deficits were greater than 100 mm. When water deficits were large, irrigation increased leaf extension more than leaf appearance or tiller number. Increasing moisture deficit had a greater effect upon tiller number than on leaf extension.     

Post-flowering tillering in contrasting light environments of two New Zealand perennial ryegrass cultivars with different perennation strategies

Post-flowering tillering responses of 'Ellett' and 'Grasslands Ruanui' perennial ryegrass ( Lolium perenne L.) cultivars after inflorescence production were studied at INRA, Lusignan in France, at near ambient light (absence of light competition, control treatment) and under shading (low-light intensity and low red–far red ratio). A dense sward containing inflorescence bearing plants of both perennial ryegrass cultivars at ambient light was cut to a height of 50 mm above ground level after which the light treatments were imposed. Forty-five days later, data were collected on the number of tillers per plant, the number of new tillers per original tiller and the dry weight of vegetative and reproductive tillers. Regardless of light treatment, cv. 'Ellett' had fewer tillers per plant, higher weight per tiller and a higher proportion of reproductive tillers than did cv. 'Grasslands Ruanui'. Number of tillers per plant and number of new tillers per tiller were consistently reduced under shade compared with the control treatment for both cultivars. When shaded, weight of reproductive tillers of cvs 'Ellett' and 'Grasslands Ruanui' were 40% and 43%, respectively, less than the control, whereas vegetative tiller weight did not change. In addition, differences between cultivars in the tillering strategy after flowering seem to be unaffected by the light environment. Thus, field observations regarding tillering of cvs 'Ellett' and 'Grasslands Ruanui' were consistent with current results suggesting different grazing managements are needed after flowering to optimize the replacement of tillers for both cultivars.     

Leaf and tiller dynamics in two competing C 3 grass species: influence of neighbours and nitrogen on morphogenetic traits

The objective of this work was to analyse the competitive interactions between Bromus willdenowii Kunth. (BW = prairie grass) and a perennial C ₃ grass Dactylis glomerata L. (DG = cocksfoot) through morphogenetic traits, during pasture establishment. Four combinations of species (pure BW, pure DG, DG flanked by BW and BW flanked by DG plants), with and without winter nitrogen fertilization, were factorially arranged in a complete random block design. Data were recorded on three tiller age cohorts of the central target plant: the main stem and those that appeared 20 and 30 days after fertilization (daf). Leaf elongation rate (LER) of the older tillers was the only variable affected by nitrogen addition. Annual neighbours, which showed higher LER than perennial ones, caused a decrease in leaf lifespan in the younger tillers and a delay in the leaf appearance rate on the main stem and on 20‐daf tillers, and the tiller appearance rate. Annual neighbours controlled leaf and tiller dynamics and therefore restricted the vertical and horizontal space occupation of the target plant. These results reinforce the advantage of using a low seeding rate for the annual species to avoid negative effects on perennial grass establishment and persistence.     

A comparison of perennial ryegrass‐ and tall fescue‐based swards with or without a cropping component for dairy production: Animal production,herbage characteristics and financial performance from a 3‐year farmlet trial

Perennial ryegrass/white clover swards have some limitations in temperate grazed dairying systems. This study tested the hypothesis that farmlets based on alternative species would be equally or more profitable than those perennial ryegrass‐based, and would produce more herbage in summer‐dry conditions. Six farmlets were established; three with perennial ryegrass‐ and three with tall fescue‐based swards. For each grass species, one farmlet was solely based on grass‐clover swards while the other two had either chicory‐red clover or lucerne crops planted on 20%–25% of the area. Animal‐ and herbage performance‐related variables were measured for 3 years, and calculated financial performance was evaluated. Using tall fescue improved total annual herbage yield compared with perennial ryegrass, but animal production and operating profit were lower. This was likely due to the reduced yield and nutritive value of tall fescue during spring and an associated decline in daily milksolids production. The deficit in spring milksolids production was never recovered, despite greater herbage production from tall fescue during summer/autumn. Incorporating chicory‐red clover or lucerne crops reduced both annual herbage and milksolids production. This reduced farm income, while increasing operating expenses as the farmlets required crop renewal and more purchased supplementary feed to maintain feed supply. Under the conditions of this study (i.e., partial irrigation, high nitrogen supply), changing the forage base from perennial ryegrass to tall fescue did not improve animal production or profitability, nor did incorporation of crops on 20%–25% of the farmlet area.     

Relationships between growth and measured weather factors among contrasting varieties of Lolium, Dactylis and Festuca species

Italian, perennial, hybrid ryegrass, tall fescue and cocksfoot were used to determine the influence of the weather upon grass growth. Throughout the spring and summer months of 1975 and 1976, weather conditions were monitored. Crop growth rate, leaf extension rate, leaf appearance rate and tillering were recorded. Natural (control), covered and irrigated treatments were applied. In spring, crop growth rates were correlated with solar radiation and temperature, but growth rates were greatest at high levels of insolation. Leaf extension rate was associated with temperature during spring. But during summer this association between temperature and leaf extension became confused as soil water deficit increased. Leaf extension rate in the tall fescue variety SI 70 was the slowest of all for a given temperature. In 1975 leaf growth was very sensitive to temperature; the rate of leaf appearance increased as temperature increased. In 1976 water deficit reduced crop growth rate in spring, and was the major factor influencing crop growth rates in all varieties during summer. Leaf extension and leaf appearance rates were both reduced by increasing soil water deficit. The ryegrasses appeared most sensitive to drought and poor recovery growth was found in the Italian RvP and the hybrid Snowdon.     

Biomass and tiller growth responses to competition between Ky31 and MaxQ Festuca arundinacea cultivars and response of Ky31 to exogenously applied liquid preparation of Neotyphodium coenophialum under glasshouse conditions

Tall fescue (Festuca arundinacea) forms a mutualistic symbiosis with the fungal endophyte Neotyphodium coenophialum which produces ergot alkaloids toxic to grazing animals. One approach to reduce pathological effects has been to introduce an exotic endophyte that does not produce toxic compounds yet still confers host‐plant benefits. We measured biomass accumulation and competition between two tall fescue cultivars with different endophytes grown in close proximity and tested if compounds from endophytes can diffuse from one plant to another. Ky31 (tall fescue with natural endophyte) and MaxQ (tall fescue with introduced exotic endophyte) were grown separately and together in a pot experiment under greenhouse conditions. The cultivars had comparable biomass production in monoculture, but when grown in mixed‐culture MaxQ had a significantly lower tiller number (2.92 ± 0.15 tillers/plant) and size (0.048 g ± 0.003) than Ky31 (4.06 ± 0.16 tillers/plant) (0.072 ± 0.002 g). Aqueous endophyte preparations were made and applied topically to E+ and E‐ Ky31. E‐ plants receiving doses of this preparation produced significantly more tillers (3 ± 0.18 tillers/plant) and larger tillers (0.074 ± 0.006 g) than untreated control plants (2.2 ± 0.13 tillers/plant) (0.0428 ± 0.0072 g). These observations suggested that a diffusible compound might induce a growth benefit conferred by the tall fescue endophyte.     

The effect of nitrogen fertilization upon the herbage production of tall fescue swards continuously grazed with sheep. 1. Herbage growth dynamics

The effect of level of nitrogen application upon the dynamics of herbage growth in a continuously grazed sward of tall fescue was investigated during two successive years. In order to obtain a large range of sward structural conditions, the experiments were carried out with two contrasting cultivars: cv. Clarìne and cv. Barcel, and, in Year 2, with two different sward heights or leaf area indices (LAIs). During each of five experimental periods (2-3 weeks), swards received either optimum (N2) or deficient (N1) N applications, were maintained at their target LAI, and leaf growth was measured on labelled tillers. With continuously defoliated tillers, N-shortage had only a small effect on the leaf elongation rate compared with tillers protected by cages. The leaf production per tiller was only slightly reduced by N shortage, and it was mainly by the means of a reduction in tiller density that the N deficiency resulted in reduced herbage growth per hectare. These results indicate that, in continuously grazed swards, in contrast with results previously found in intermittently defoliated swards, leaf elongation is not the only important component of difference in herbage growth and that the promotion of tillering rate is an additional pathway for N response in such management regimes.     

The physiology of tiller death in grasses. 2. Causes of tiller death in a grass sward

The causes of tiller death in a 2-year-old perennial ryegrass sward were examined between April and August 1977. Physiological causes accounted for most tiller deaths and grazing by slugs and rodents was more important than the damage caused by stem-boring larvae. Tillers which died were mainly small and vegetative, although some flowering tillers died prematurely. Low nutrient status delayed but did not prevent tiller death. Using ¹⁴CO₂ it was shown that small tillers fixed relatively less radiocarbon than did larger tillers and they did not receive much support for their carbon economy. Selective defoliation showed that in April defoliated tillers imported radiocarbon from undefoliated tillers but that in July at anthesis an undefoliated reproductive tiller retained most of the carbon it fixed, despite its vascular association with defoliated tillers. It appears that much of the tiller death during the period April-August is due to the failure of the more favourably placed tillers to support other tillers which are heavily shaded.     

Tiller production in cocksfoot (Dactylis glomerata) and tall fescue (Festuca arundinacea) growing along a light gradient

Pasture managers seek to balance leaf appearance with utilization to sustain sward productivity while meeting livestock nutritional needs. Achieving this in silvopasture must account for the influence of light and defoliation on tillering. We determined tiller production, as a function of light availability and clipping height, for two forage grasses adapted to cool, humid temperate conditions of the Appalachian region of the USA. Tiller production of cocksfoot (orchard grass) (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) was greatest in unshaded and least in shaded sites, irrespective of residual clipping height. Juvenile plants produced more than twice as many tillers as mature plants, with differences accentuated by site, reflecting a shift in reproductive and resource‐use strategies. Trends in tiller production were as follows: cocksfoot > tall fescue; 10‐cm > 5‐cm residual clipping height; and unshaded > partially shaded > densely shaded sites. Tiller production reaches maximum earlier in the woodlot site, regardless of species or clipping height, than at the unshaded site. Plants at the wooded site extended leaves quickly, sustaining herbage production, but had less non‐structural carbohydrate and fewer tillers. Cocksfoot, but not tall fescue, sustained leaf and tiller production in the shaded sites, suggesting that cocksfoot is suited for use in silvopasture in this region.     

Is there a tiller morphology ideotype for yield differences in perennial ryegrass (Lolium perenne L.)?

The objectives of this study were to measure the variability in ‘realized’ tiller morphology and identify whether there are emergent generalizations about a tiller ideotype for productivity or survival. Morphological traits during the vegetative growth stage were measured for 2 years in the field for eight perennial ryegrass cultivars: six diploid and two tetraploid cultivars under low and high nitrogen fertilizer (50 and 225 kg N ha^?1 year^?1 respectively). Traits measured were lamina width, length and area; pseudo‐stem length and diameter; an index of tiller shape; tiller dry weight; tiller density; and herbage mass. Almost all the traits differed significantly between cultivars and significant correlations were found between the 2 years. Principal component analysis identified that tiller morphology and dry‐matter yield were independent. No trait associations indicating alternative cultivar‐specific tiller morphologies were detected but cultivars differed in tiller size. The patterns of change between the 2 years indicated a possible morphological trajectory as swards age. The genetic compensatory relationship between tiller size and density had a 1:1 slope, indicative of constant yield. This implies that larger tillers would be more leafy, and higher leafiness of tetraploid over diploid cultivars was confirmed by the leaf:non‐leaf ratio and tiller shape index.