An Analysis of the Effect of Guayakí Yerba Mate on Plant Growth
Despite the documented negative effects of caffeine on plant growth, gardening experts
recommend watering plants with black coffee since coffee contains nutrients also found in plant
fertilizers. The objective of our study was to determine whether varying dilutions of another
common caffeinated drink, Guayakí Yerba Mate (GYM), would promote shoot growth in green
onions. In this experiment, green onions were watered with different dilutions of GYM (25%,
50%, 75%, or 100% concentration) for our treatment groups and tap water for our control group.
We hypothesized that if GYM is beneficial for plant growth, then the green onions placed in the
100% GYM solution would have the greatest shoot growth after a two-week period compared to
the green onions in the diluted solutions and tap water. The mean shoot growth for each group
was as follows: control = 24.2 cm, 25% = 10.13 cm, 50% = 4.96 cm, 75% = 4.12 cm, 100% =
3.02 cm. A one-way ANOVA test followed by a Tukey’s multiple comparison test showed that
the mean shoot growth of the control group was significantly greater than each of the four
treatment groups (p<0.0001). In conclusion, our hypothesis was not supported, and we found that
GYM negatively affected the growth of the green onion shoots due to the impairment of root
growth and function.