This is an overview of the multiple ways in which pasture plants are categorised and the characteristics of those groups.
Perennial species regrow each year from root reserves while annuals grow from a seed each year. In areas of higher rainfall, perennials can have the advantage of already being established and being able to respond to favourable seasonal conditions throughout the year. In contrast, annuals can be sown (or may naturally re-sow themselves) to achieve a specific feeding goal, without the need to survive a harsh summer or winter. Biennials are plants that take two years to complete their life cycle, or one year in less favourable conditions.
Grasses belong to the most widespread and successful family of plants, the Poaceae. Other terms are monocot and narrow leaf. Nearly all pastures in NSW are dominated by grasses. Legumes, which include clovers and medics, are a family of broadleaf (or dicot) plants that can produce their own nitrogen. They do this with the help of Rhizobium bacteria, which live in nodules attached to the plant’s root system. Rhizobia capture (or ‘fix’) atmospheric nitrogen and convert it into a form that is available to plants. In most cases, a pasture sward with both grasses and legumes is desirable.
Native grasses have evolved in Australia, whereas introduced, or exotic species have evolved elsewhere. Naturalised species are those that originate overseas but are now established in parts of Australia, where they persist without human intervention.
Temperate grasses and legumes and tropical legumes use the standard C3 biochemical pathway for photosynthesis whereas tropical grasses use the C4 pathway. C4 species have greater water use efficiency but, for the same plant material (e.g. leaf) at the same stage of growth, they have lower feed quality than C3 species because of the energy needed to achieve this greater efficiency.
This term is sometimes used to describe C3 grasses which regularly grow year round. However, both C3 and C4 perennials are able to grow throughout the year - as long as conditions are favourable.
These grasses can grow in cooler conditions than tropicals; and they tend to be of higher feed quality. Most growth is in spring but they also grow in autumn and winter. Perennial types can grow in summer, if conditions are favourable.
These grasses tolerate hot and dry conditions better than temperate species. Most growth is in summer and autumn. Tropical species tend to grow very slowly in cool conditions (<150C) and they are strongly affected by frost.
These plants produce their own nitrogen, in association with Rhizobium bacteria, and can grow in cool conditions. Like temperate grasses, most growth is in spring but they also grow in autumn and winter. Perennial types can grow in summer, if conditions are favourable.
These plants produce their own nitrogen, in association with Rhizobium bacteria, and tolerate heat better than temperate legumes. Most growth is in summer and autumn. They grow very slowly in cool conditions and are strongly affected by frost.
These may be tropical or temperate species. Most of the agriculturally-useful native grasses are tropical perennials. Native grasses are well-adapted to their environment but their seed is, in general, difficult or impossible to obtain. When compared to introduced species growing in favourable environments, the productivity of native grasses can be very low.
These non-woody plants are a miscellaneous group of species that are neither grasses nor legumes. They can be productive and of good feed quality.
These perennial woody plants are browsed by animals. They are common over large areas of the dry rangelands of western NSW.