Influence of shade and cold stratification on germination success of vegetative propagules from multiple Butomus umbellatus genotypes

Three experimental trials were conducted to investigate the influence of shade and cold stratification on germination success of vegetative propagules from multiple Butomus umbellatus genotypes. Shade level did not significantly impact germination of propagules in trial 1 (p=0.16); however, significant differences (p<0.0001) in germination percentages at the conclusion of the study were detected between genotypes. Rhizome segments of the triploid genotype one (G1) had the highest mean germination (95±1%); whereas bulbils of the diploid genotypes three (G3), four (G4), and five (G5) germinated to 9±2%, 1±1%, and 15±2%, respectively. Trial 2 focused on bulbils from G3, G4, and G5 diploid plants that were stratified at 4℃ for 35d. Like Trial 1, shade level was not significant (p=0.19) relative to the overall germination of cold-stratified bulbils. However, cold-stratified bulbils exhibited a much higher mean germination (≥93%) for all three genotypes. In Trial 3, the cold stratification treatments were significant and positively correlated to overall germination for G4 (p=0.005, r=0.77) and G5 (p=0.002, r=0.82), but not G3 (p=0.22, r=0.40) bulbils. Germination time significantly differed between genotypes in all cold-stratification treatments except for the 0, 120, and 180-day treatments. These studies demonstrate that a high percentage of vegetative propagules produced by B. umbellatus are capable of successfully germinating under laboratory conditions, but some require extended periods of cold exposure. Given that a single diploid bulbil can produce thousands of bulbils within a growing season; long term management of this species will need to be focused towards limiting bulbil production.