Inflorescence
After tillers have reached the boot stage of reproductive development, the inflorescence or flowering structures become visible. Let’s take some time now to discuss these structures in detail. The type of inflorescence a plant has can be used in helping to identify it. Generally, grasses are classified as having one of three inflorescence types including a spike, raceme, or a panicle that differ based on the degree of branching and arrangement of spikelets. Of the three inflorescence types, racemes are least common and thus are not illustrated. The pictures that follow illustrate a spike with flowers (spikelets) arranged on an unbranched rachis of crested and intermediate wheatgrasses (Exhibit 16 &17) and a panicle of switchgrass in which the flowers (spikelets) occur on a branched and rebranched rachis (Exhibit 18 &19). Notice the spike of crested and intermediate wheatgrasses is more compact, whereas a panicle is more open, as seen with switchgrass.
Exhibit 16. Spike inflorescences of intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] and crested wheatgrass [Agropyron cristatum (L.) Gaertn.]. Photo credit: John Guretzky, University of Nebraska-Lincoln
Exhibit 17. Spike inflorescence of crested wheatgrass (Agropyron cristatum). Photo credit: John Guretzky, University of Nebraska-Lincoln
Exhibit 18. Panicle inflorescence of switchgrass (Panicum virgatum L.). Photo credit: John Guretzky, University of Nebraska-Lincoln
Exhibit 19. Spikelets along branched rachis of the panicle inflorescence of switchgrass (Panicum virgatum L.). Photo credit: John Guretzky, University of Nebraska-Lincoln