Seed Production Stage

The final stages in a growing season for grasses are seed production and leaf senescence and loss.  It is characterized by the continued filling and maturation of seeds, as seen in Exhibit 20.   This stage is important for the plant to produce offspring.  After seed production, the plant undergoes senescence and remobilizes nutrients including nitrogen, phosphorus, and potassium to belowground storage organs.  Eventually leaves are dropped and biomass is lost to the soil surface.  During this stage, perennial grasses may be grazed without detriment to the plant, but forage quality is quite poor.  Post seed production, and later yet after a killing frost, represents an ideal time for harvesting of perennial grasses in expanding biomass energy systems because biomass yields are highest and nutrient levels are lowest at this time.  By allowing plants to recycle their nutrients, less fertilization will be required to maximize subsequent biomass yields.

Exhibit 20.  Field of warm-season grasses ready for harvest. Photo credit: John Guretzky, University of Nebraska-Lincoln