Brassica elongata ssp. integrifolia seed germination.

Repeatedly during the late 19th and early 20 th century, exotic weeds were introduced to the sagebrush (Artemisia)/bunchgrass rangelands of the Great Basin. Once established these weeds became invasive, spreading without the conscious efforts of humans. Brassica elongata ssp. integrifolia (Boiss.) Breistr. offers evidence this process of introduction still continues. Brassica elongata ssp. integrifolia is native to southeastern Europe and Asia. It was first collected in North America near Portland, Ore. in 1911. This initial infestation apparently did not persist. The next collection was near Eureka, Nev. in 1968. Currently, Brassica elongata ssp. integrifolia has spread about 200 km east and west along U S Highway 50 and 100 km north and south of the highway along secondary roads. As a first step in understanding the seed and seedbed ecology of this new invasive weed we investigated the germination of seeds at a wide range of constant and alternating temperatures. This plant produces abundant seeds that germinate over a wide range of constant and alternating temperatures. Maximum germination ranged from 84 to 94% depending on the year of seed production. Germination was extremely limited at very cold seedbed temperatures and low at the cold category of seedbed temperatures. Germination at these temperature is a competitive advantage for other exotic species on Great Basin rangelands. DOI:10.2458/azu_jrm_v56i6_young