Environmental effects on asexual reproduction in Arundo donax

Arundo donax L. (giant reed) is an invasive perennial plant that has spread widely in riparian areas in California, where it has altered wildlife habi tats, created a fire hazard, compromised water conservation efforts, and af fected flood control. Currently, physical removal is the primary means of c ontrolling this weed, which is ineffective because of prolific asexual repr oduction from an extensive rhizome system. We conducted controlled experime nts on the sprouting potential of vegetative propagules, effects of storage duration and conditions on sprouting, and survival and growth of propagule s in various soil types and moisture regimens. Sprouting and regrowth varie d greatly with propagule type and size and with treatment and duration of s torage after removal from the plant. Over 90% of stem and rhizome pieces wi th at least one node sprouted. Stem sprouting was affected by prior storage duration, temperature and moisture, whereas only storage duration and mois ture affected rhizome sprouting. Sprouting was reduced by drying propagules at 30 degrees C for 1 week and by storage in a soil slurry. After 16 weeks , even propagules maintained optimally in moist soil showed reduced sprouti ng. Rhizome pieces sprouted readily from a soil depth of 25 cm, whereas ste m pieces sprouted from less than 10 cm. Responsiveness of asexual reproduct ion in A. donax to environmental cues suggests that mechanical control can be improved by careful timing and treatment of cut biomass pieces to minimi ze or inhibit sprouting.