Agronomy Journal • Volume 110, Issue 6 • 2018 2159 P erennial ryegrass (Lolium perenne L.) is known as a non-creeping, bunch-type species (Beard, 1973). However, as reported by Wipf and Singh (2015), several studies documented the occurrence of a ‘stoloniferous’ or ‘rhi- zomatous’ habit in perennial ryegrass with stolons or rhizomes that cannot be considered “true stolons”. Tese vegetative organs are actually pseudo-stolons or pseudo-rhizomes. As discussed by Wipf and Singh (2015), these structures are actually aerial culms that get trampled or pushed down, and then begin to root at nodes, or crowns that become buried by soil, dung, mulch, or earthworm casts with leaves dying and decomposing leaving only the culm and roots at nodes. Plants of perennial ryegrass with “rhizomatous habit of growth” were found by Mitchell (1956) and Kydd (1966) in pastures. Kydd (1966), studied the efect of stocking rate on perennial ryegrass tillers and observed the for- mation of elongated stems under high stocking rate. Simons et al. (1974) demonstrated that increasing cutting height and straw mulch encouraged aerial tiller production diferently according to genotype. Harris et al. (1979) found crowns below the soil surface connected to what they termed “underground stolons” (i.e., pseudo-rhizomatous) and discussed the defnition of the term “stolon” and “rhizome” and “aerial tillers”. Furthermore, they investigated the distribution of 18 morphologically identi- fed ryegrass types grown as spaced plants, and observed that those genotypes had vegetative tillers with elongated internodes on the periphery of the tiller clump spreading to form patches. Similar structures were found by Mitchell (1956) in livestock grazed perennial ryegrass plants. New turf-type cultivars of perennial ryegrass with prostrate growth habits and lateral- spreading shoots (creeping-type) have recently been developed (Charbonneau and Brownbridge, 2013). Wipf and Singh (2015) fled a patent for “ Lolium perenne subsp. stoloniferum with an aggressive determinate-stoloniferous growth habit,” and described this new subspecies as having true stolons. Perennial ryegrass is widely used as a constituent of winter sports turfgrass in moderate temperature regions and in transi- tion areas (Puhalla et al., 1999), because it performs well during cooler months (Bertrand et al., 2013) when athletic felds are principally used, and because of its excellent wear resistance, quick establishment, and tolerance to close mowing (Goatley et al., 2008; Puhalla et al., 1999). Harris et al. (1979) reported Stolon Development in Four Turf-Type Perennial Ryegrass Cultivars Cristina Pornaro,* Alessandro Menegon, and Stefano Macolino Published in Agron. J. 110:2159–2164 (2018) doi:10.2134/agronj2018.02.0138 Available freely online through the author-supported open access option Copyright © 2018 by the American Society of Agronomy 5585 Guilford Road, Madison, WI 53711 USA Tis is an open access article distributed under the CC BY license (https://creativecommons.org/licenses/by/4.0/) AbsTRAcT Perennial ryegrass (Lolium perenne L.) is known as a non-creep- ing, bunch-type species. However, several studies documented the occurrence of a ‘stoloniferous’ or ‘rhizomatous’ habit in this species. Tis research aimed to study the stolon development in creeping (‘Sienna’ and ‘RPR’) and non-creeping (‘Apple SGL’ and ‘Pizzaz 2’) type cultivars of perennial ryegrass seeded at three rates (10, 20, and 30 g m –2 ). Plots were seeded in September 2015 and from December 2015 to July 2017, two core samples (8 cm diameter and 5 cm depth) were collected from each plot every other month. Stolon length density, weight density, and average diameter were estimated, and the specifc weight was calculated. Our results demonstrated the presence of stolons in all the tested cultivars. Te cultivar 'Sienna' showed the highest stolon produc- tion followed by ‘Pizzaz 2’ and ‘Apple SGL,’ whereas ‘RPR’ dis- played the lowest. Te cultivars started to produce stolons in the spring of the frst year afer establishment, reached the highest level in late summer and maintained production until termina- tion of the study. Te lowest seeding rate favored stolon produc- tion and their growth in diameter as it produced the highest length density, specifc weight, and average diameter. C. Pornaro, S. Macolino, Univ. of Padova, Dep. of Agronomy, Food, Natural resources, Animals, and Environment, viale dell’Università 16, Legnaro, Padova, Italy; A. Menegon, Padana Sementi Elette Srl, Via Vittorio Veneto, 85, Tombolo, Padova, Italy. Received 28 Feb. 2018. Accepted 5 Sept. 2018. *Corresponding author (cristina. pornaro@unipd.it). core Ideas • We demonstrate the presence of stolons in all studied cultivars. • ‘Sienna’ showed more stolons than ‘RPR’ in terms of length and weight density. • ‘Sienna’ reached higher stolon weight, but not length, density than ‘Pizzaz 2’. • Stolons were formed in April afer the establishment, and rapidly increased in June. • Te lower seeding rate favor production of stolons and their growth in diameter. eUROPeAn TURfGRAss sOcIeTY cOnfeRence Published October 18, 2018