Jubatagrass is one of the most invasive nonnative species along sensitive natural coastal sites of California. This study was designed to understand the biology of reproduction and seed longevity under field conditions. Jubatagrass can produce over 100,000 wind-dispersed seeds from a single inflorescence. Seeds are produced apomictically, and germination is directly related to seed size. Of the total seeds produced, only 20 to 30% were of ample size to readily germinate when exposed to light and under a temperature range similar to coastal environments. Seeds not exposed to light also germinated but at about 30% the level of light-exposed seeds. This suggests that exposed disturbed coastal sites with moderate temperatures have high potential for germination and establishment of jubatagrass. The percentages of germinable and viable seeds were not significantly different, indicating that jubatagrass does not have a primary dormancy. This was supported by field experiments demonstrating that seeds do not persist under natural conditions for more than 6 mo. These results indicate that an intensive 1-yr control program targeting established seedlings and mature plants should sufficiently manage existing populations. However, effective long-term management of jubatagrass must focus on anticipating environments susceptible to invasion, reducing new seed recruitment, and preventing subsequent seed germination and seedling establishment.

Nomenclature: Jubatagrass, Cortaderia jubata (Lemoine) Stapf.