Sial in geology is the upper layer of the earths crust. Because the Earth's crust behaves like a liquid, the rocks in the sial tend to be the least dense, in the same way yoâ¦u see when you float oil on water and values of 2700 to 2800 kg/m3 are typical. The rocks are rich in silicate and aluminum minerals.
Perennial ryegrass is planted as permanent turf or lawn grass and to overseed warm season grasses while they are in winter dormancy. Perennial ryegrass seed is also mixed with other cool season grasses to provide more density to the dominate grass in the mixture.
Biennial are plants whose lifecycle spans two years, so they flower and produce seeds in their second year. A familiar biennial is foxglove, Digitalis purpurea. Some plants grown as biennials are, botanically speaking, short-lived perennials, for example, sweet william and wallflower.ardy annuals are plants that go through their entire life cycle in one season and that can be sown outside in the open garden in spring where it is to flower, for example, Centaurea cyanus â cornflower.