Successful Propagation of Miscanthus x Giganteus by Rhizomes.

Miscanthus x giganetus (M. x g.) is a very large perennial grass currently being studied as a potential biomass crop, due to its extremely large biomass yields.  M. x g. is more challenging to establish due to its triploid seed sterility.  Therefore, it must be propagated vegetatively.  Currently, the most common method of propagation is via lifting and replanting of rhizomes.  Therefore, optimal conditions for harvest, storage, and replanting are critical to initial establishment.  Since M. x g  is a perennial plant, it stores nutrients and carbohydrates in its underground root and rhizome mass for overwintering, then uses these reserves to regrow each spring.  At the University of Illinois, we have found that lifting rhizomes for propagation after M. x g. has started to grow in the spring drastically reduces the ability of the rhizomes to re-sprout again after replanting.  The hypothesis is that M. x g. plants expend their carbohydrate reserves in getting the plant above ground each spring.  Once these reserves are used up, the rhizomes do not have enough carbohydrates stored to allow re-sprouting again.  Therefore, we initiated a study to examine how the carbohydrate levels withing M. x g. rhizomes vary throughout the year.  In 2009, rhizomes were harvested from random M. x g. plants in an established stand at varying intervals.  In 2010, rhizomes are being collected bi-weekly to determine carbohydrate content as well as rhizome re-germination ability.  Results will show how rhizome carbohydrate content fluctuates throughout the year and what impact it has on the rhizome’s ability to re-sprout.  In addition, once harvested, rhizome moisture is important to long-term viability in storage.  Our work has shown the critical threshold for rhizome moisture to be near 50%.  When moisture drops below this level, re-sprouting is negatively impacted.  Studies will show optimal storage conditions and lengths for retaining optimum rhizome moisture levels.  Finally, first-year plantings tend to be more susceptible to winter kill.  Prelimiary results show a difference in soil temperature between first-, second-, and third-year stands of M. x g. in December 2009, which could have an effect on winter survival.