The length of time from seed sowing to flowering and effects of mowing on the growth of Rudbeckia laciniata L.

Abstract

We in vestigated the effects of mowing on the growth of Rudbeckia laciniata L., an invasive alien species in Japan, and discussed the possibility of eradicating this species by this method. Seedlings of R. laciniata were cultivated in pots, and the time from seed sowing until flowering was examined. Further, the effect of eight mowing treatments with varying frequency and time of mowing on the plant height, number of stems, percentage of flowering individuals, and number of flowers per individual were investigated. Since the growth of plants from the spring season onward is affected by the belowground biomass accumulated during the previous year, we also measured the dry weights of the above- and below-ground parts of plants in all the treatments at the end of November. The period from seed sowing to flowering for R. laciniata was two years. In the non-mowing treatment two years after seed sowing, the plant height was 118 cm and all individuals produced flowers, with an average of 11 flowers per individual. The mowing treatment at the end of June and August (i.e., mowing twice a year) was reliably shown to inhibit flowering and subsequent seed set. However, mowing even three times a year-end of June, August, and October, could not exhaust the belowground biomass of the plants. Our study results indicate that it is difficult to eradicate R. laciniata by mowing alone. Therefore, for effective elimination of this species, firstly, flowering and seed set should be controlled by mowing large areas, followed by the removal of individual plants as much as possible, by hand pulling.