The previous posters made many good points, but I see it a little differently than Mark. It would be good to measure the weight the rhizomes before planting and compare the means among treatments. However, I would care less about the statistical significance of the differences than the magnitude. You want the differences in initial weight among treatments to be small, period. Differences among treatments may or may not be statistically significant owing to the magnitude of the differences, the variability among rhizomes, and the number of observations. Your only interested in the magnitude of the differences in this case.
Cheers, Peter
