Hundreds of years ago, the San Joaquin flowed freely through a grass and marsh-dominated region variously known as the "California prairie", "California annual grassland", or "Central Valley grasslands". It is widely believed that the dominant grass species throughout the San Joaquin River valley and Tulare Basin, as well as the Sacramento Valley, the Sierra foothills and Coast Ranges, was Nassella pulchra, a type of bunchgrass more commonly known as purple needlegrass. Today, this vegetation community exists only in isolated pockets because of development of the valley for agriculture, and in much of the remnant open areas where it once thrived, now grows introduced flora such as annual rye and wild oat. The vegetation communities created by the introduced grasses are sometimes referred to as "valley grassland", which is highly seasonal but is spread throughout the Central Valley from near Redding to south of Bakersfield. These grasses all thrive in the Mediterranean climate that dominates much of the San Joaquin Valley.