Southern tarplant (Centromadia parryi ssp. australis) is a native, annual herb, a Covered Species under the Southern Subregion Habitat Conservation Plan (HCP), and is designated as a 1B.1 rare plant species by the California Native Plant Society. The species is a member of the sunflower family (Asteraceae) and occurs in vernal pools, alkali playas, alkali grasslands, and disturbed areas that exhibit mildly alkaline/saline soils. It has stiff bristly stems and can reach heights of up to 2.4 feet and is characterized by many disk flowers with yellow corollas and brown or black anthers. The species typically flowers as early as June and sometimes into October, with peak flowering varying according to seasonal rainfall patterns.

As part of the HCP Management & Monitoring Program, the Rancho Mission Viejo Land Trust monitors the extent and general health of existing southern tarplant populations by conducting surveys to document the number of flowering individuals, confirm and map occupied locations and dense populations (Core Areas), and record general habitat conditions such as presence of non-native species, weather, water quality, and runoff. In 2025, the surveys resulted in the highest number of southern tarplant recorded since monitoring began in 2014 with a total of 56,556 individuals being detected in all Core Areas on the Nature Reserve.