Frond growth and development of Pentagramma triangularis subsp. triangularis was examined in canyon populations in Ventura County, California during the winter growing season of 2003. Fronds developed from emerging croziers to full size within 35 days and reached sexual maturity by 70 days. Frond growth occured in two stages with stipe elongation nearly complete when the crozier began to unfurl, about a week before full maturation of the entire frond. Discernable developmental stages are described as well as their respective ages. Fern growth occurred both prior to and after the study frond monitoring period, indicating multiple growth flushes throughout the growing season, possibly related to rain events. Based on these preliminary results, suggestions are offered for further study.