Perennial grasses go through very defined stages of growth, each of which are marked by certain visible characteristics. Beginning as a seed, the grass goes through germination, and then produces leaves during the vegetative stage. During this stage not much biomass is present, but the leaves are high in nutritive value. Despite high nutritive value, it is important to avoid close grazing until the perennial grass has accummulated the carbohydrate and protein reserves to recover from such defoliation.
The elongation stage results in the appearance of stems and palpable nodes. Although perennial grasses have more biomass at this point, low energy stores are in stem bases, rhizomes and roots, and the elevated stem apex makes the grasses ill-suited for grazing or harvest.
Following elongation, many perennial grasses enter the reproductive stage where stems fully elongate and the shoot apexes undergo differentiation to produce the inflorescence (with the exception of sterile tillers). Since carbohydrate and protein levels in herbage and storage organs have accumulated, grazing or harvesting for biomass at this time will not hurt the plants if appropriate time for regrowth is allowed.
If not harvested during the reproductive stage, perennial grasses will go on to utilize proteins and carbohydrates to produce seed. Although seed can be harvested and planted to establish new stands, new tillers produced from axillary buds provide the next generation of perennial grasses.
Throughout the growth period, although most of what we see is well above ground, horizontal tillers and roots contribute to growth. Stolons and rhizomes contribute to establishment and spread of grasses, while roots take up water and nutrients from the soil for plant growth. These less-visible plant structures and their associated functions are the primary source of new tillers and critical for the growth and development of perennial grasses.
Using this knowledge of perennial grass growth and development will allow you to apply scientific concepts to improve management of perennial grasses for traditional pasture and range or for biomass energy crops.