Tall fescue seedlings are relatively slow to establish themselves, especially when compared with those of other Lolium species, such as the ryegrasses. They are even slower to establish when soil temperatures (Hamilton-Manns et al., 1995) in the top 20 to 30 cm are low (<10-12°C) (Fig. 5-1) because of soil characteristics, earliness in the season, poor exposure to the sun, and soil moisture contents. Slow germination increases possible weed competition, which should always be eliminated. In regions with dry autumns it is best to wait for a good rain to induce a flush of weed seed germination, then to wait another 2 wk before spraying weeds and sowing. This will often mean sowing in April or May (Charles et al., 1991) in the southern hemisphere, when the soil temperature could already be below 12°C. Seedlings are also sensitive to drought and high temperatures (>25°C) (see Chapter 4).
Fig. 5-1. Effect of soil temperature on the germination of four grass species (Charles et al., 1991).