RARE PLANT TREASURE HUNT REPORT

SANTA ANA RIVER BASIN, EAST OF YORBA LINDA, JUNE 7, 2015

A group of eleven CNPS members, biologists and enthusiasts assembled for a day of plant exploration. Our goal was to relocate plants with a California Rare Plant Rank, all within a small section of Orange County. Each of these plants is represented only with historical records in this area, with most records dating back many decades.

Our survey areas were within the Santa Ana River basin, in the region East of Yorba Linda and just west of the Orange County line. Our primary target species were Eriastrum densifolium ssp. sanctorum – Santa Ana River woolly-star (U.S Endangered, CRPR 1B.1) and Abronia villosa var. aurita - yellow hairy sand verbena. (CRPR 1B.1). 

The Eriastrum has not been recorded in OC since 1929, but has recent records from as near as Norco, just ten miles upstream. The Abronia formerly occupied similar sandy alluvial soils in this area, but records have been absent from here since the 1930’s.

We believe there still is suitable habitat for both of these species west of Prado Dam. The Santa Ana River is the largest watershed in Southern California, covering nearly 3,000 square miles and draining portions of Los Angeles, Riverside, San Bernardino and Orange counties. The river, once free-flowing has largely been channelized and tamed, especially west of Prado Dam. However, in the areas of the survey the river is still allowed to wander, refreshing the alluvial soils and sandy benches required for many of the plants that were a part of our search. This is especially true in an area known as locally as Horseshoe Bend. In addition, we also surveyed the alluvial soils and similar habitat in areas both east and west of Gypsum Canyon Road.

Other than the woolly-star and sand verbena, other native plants we were attempting to re-locate included the locally rare Eriogonum thurberi (recorded in this area as recently as 1979), Acer negundo, Chaenactis glabriuscula var. lanosa, Ambrosia confertiflora, Eustoma exaltatum, Glycyrrhiza lepidota, Opuntia basilaris, Gutierrezia sarothrae,Sagittaria latifolia, Calystegia sepium ssp. limnophila, Sparganium eurycarpum  and even the endangered Astragalus brauntonii. Each of these, although not all CRPR plants, either only have historical records in this area or have very few Orange County records.

RESULTS

It was a full day in the field. We began at 8am with a review and discussion of each of our target species. Then, we entered our first survey area at Horseshoe Bend and fanned out across the land. We walked slowly and in a somewhat methodical pattern through the survey area, navigating through the brush and the uneven terrain. We paused as we went, resolving any uncertain plants, generating data points and taking photographic records as needed. As a group, we covered the area rather thoroughly.

We then drove a short distance east, where we gained access through a private landowner to more suitable habitat. Again, the team searched diligently in an organized and thorough manner, recording additional plants.

In spite of a great effort, we were unable to locate either of our two primary targets, Santa Ana River woolly-star or yellow hairy sand verbena. We knew the odds of finding these were small, but our enthusiasm was not diminished. Thank you to all of our great volunteer Rare Plant Treasure Hunters: