Species: Holcus lanatus

FLORAL BIOLOGY <br><br>In North America, flowering occurs June through August (Septem- ber). H. LANATUS is wind pollinated and predominantly an outcrossing species. Successful self-fertilization occurs only occasionally and is impossible in some plants (Beddows 1931). During anthesis the panicle opens from the apex down and closes likewise (Tutin et al. 1964). <br><br>SEED PRODUCTION <br><br>In England, HOLCUS LANATUS seeds are shed from June to September (Mortimer 1976). The plants require vernalization to flower, but this process is enhanced and, to a small extent, replaced by short- day treatment (Watt 1977). It flowers and produces seeds from the second year onwards and behaves as a "paucennial." In places with reduced competition, the plant will often die after a few years, particularly following luxuriant flowering. In southern Europe, very short-lived races that flower the first year are found in dry habitats. In northern races, the plants require a period of vegetative growth prior to flowering in the second year (Bocher and Larsen 1958). HOLCUS LANATUS also exhibits variation in culm length and growth habit. In exposed maritime habitats, it grows as a low plant, while farther inland, the plants are more erect with tall culms (Bocher and Larsen 1958). <br><br>Trapaidze and Gogiya (1981) report up to 850 wind-dispersed seeds per plant in the Soviet Union. In England, Watt (1976) found production of up to 240,000 seeds per plant, most of which germinated shortly after landing on moist soils. <br><br>SEED GERMINATION <br><br>Williams (1983) found that when stored under dry, shaded conditions, velvet grass seeds remained viable for at least 48 weeks with 90-99% germination. Trapaidze and Gogiya (1981) found a germination rate of 95% for the first two years after seed harvest. Both vertebrates and earthworms appear to significantly reduce velvet grass populations by their burial or consumption of seeds (Mortimer 1976). When the seeds were buried, only 3% of them were still viable after a year. Seeds buried at a depth of 1-2 cm had a much higher chance of emergence than those at a depth of 3 cm (Williams 1983). In the Soviet Union, HOLCUS seeds showed 87% germination rate on the ground surface, 76% at a depth of 1 cm, and only 5% germination at 2 cm (Trapaidze and Gogiya 1981). HOLCUS LANATUS seeds are thus apparently not innately dormant, though certain field conditions may enforce dormancy (Williams 1983). Even though most of the seeds are nondormant, the potential number of seeds produced by each plant is so high that even a 1% level of innate or enforced dormancy would result in a large amount of buried viable seed (Watt 1976). The species can thus exist in large numbers in a seed bank, even if it is not an important plant on a given site (Roberts 1982). <br><br>Seed germination can occur at 7-8 C (Trapaidze and Gogiya 1981). Thompson and Whatley (1984) suggest that burying the seeds may induce a requirement for fluctuating temperatures of greater than 19 C. The result is that HOLCUS LANATUS seeds germinate more readily in larger canopy gaps (wider than 25 cm) where their survival chances are improved (Thompson 1977). Mortimer (1976) estimates that when various mortality factors are taken into consideration, each HOLCUS LANATUS plant can produce 9.9 adult plants the following year. <br><br>HOLCUS LANATUS is not usually considered a stoloniferous species, but regeneration can occur by the formation of decumbent tillers in late summer that subsequently produce roots and shoots at the nodes. Growth of these shoots may be enhanced by grazing or mowing, but root growth does not appear to be affected (Watt and Haggar 1980a).