Development of tillers formed an inflorescence node at flowering stage of annual bluegrass (Poa annua L.) was observed by microscope aspect. In young tillers on the 3rd node from the tip, a prophyll primodium was formed at booting stage, and the young floret primodium was formed at terminal flowering stage. Moreover, it was suggested that prophyll, young panicle, primary branch, secondary branch and young floret are developed in the inflorescence nodes within about 12 days under a favorable condition.
We demonstrated that mowing three times a year (i.e., in May, July, and September) is adequate for ensuring that light conditions are necessary for the growth of Zoysia japonica ‘Asagake’ on grass-covered levees. Mowing grass-covered levees as few as three times a year resulted in a strong tendency for plant groups to grow higher than mowing every month from April to October (seven times a year). At the same time, the relative photon flux density immediately above the plant canopy of Z. japonica remained similar under both mowing regimes. For the experimental period, Zoysia’s cover rates of mowing three times a year was lower than that of mowing every month. However, mowing three times a year showed 75% coverage on Jul. and Sept. Furthermore, mowing only in May resulted in reduced Z. japonica cover due to the effects of shading by cogon grass (Imperata cylindrica) and Japanese mugwort (Artemisia indica) from August onward. Mowing three times a year removed cogon grass and Japanese mugwort in July, ensuring that light conditions are favorable for Z. japonica growth.