San Diego Marsh Elder [Iva hayesiana Gray]
Listing CNPS List 2 R-E-D Code 2-2-1
State/Federal. Status --/C2 ASTERACEAE Apr.-Sep.
Global Rank G3? State Rank S3?
Distribution: San Diego County; Baja California, Mexico
Habitat: Creeks or intermittent streambeds are the preferred habitat for this low-growing, conspicuous shrub. It is rarely situated on seeps near creeks. Typically, the riparian canopy is open allowing for substantial sunlight to reach the marsh elder. Sandy alluvial embankments with cobbles are frequently utilized. Within the southwestern portion of the County this plant may occur in steep watercourses where other riparian vegetation is not present. While soils are usually mapped as Riverwash, these steeper locales can include various series including San Miguel-Exchequer or Huerhuero loams.
Known Sites: The highest concentrations for this shrub occur in the Otay River from Salt Creek in the east, west to Beyer Boulevard. It is found along intermittent streams around Lower Otay Lake, and is to be looked for in any drainage in the south County near the coast. San Diego Marsh Elder is uncommon on Otay Mesa in Spring Canyon and other nearby seasonal watercourses. It is fairly common in drainages on Otay Mountain. This shrub is also found within most drainages on the northern slopes of Otay Mountain, nearby Mother Miguel Mountain, the creek south of Proctor Valley Road and west of Rolling Ridge Road, and in Little Hansen Creek; it is locally common along Peñasquitos Creek from just east of Interstate 15 west to Interstate 5, and uncommon along Escondido Creek and its tributaries. Generally, the farther north one goes the smaller and more localized the populations such as those on San Marcos Creek below the dam. A vigorous population grows on an well-developed riparian creek 1 mile west of Lake Hodges and south of Del Dios Highway and the San Dieguito River. Small populations were seen in a canyon drainage west of Black Mountain Road and north of Peñasquitos Canyon, east of Fairbanks Ranch near Lusardi Canyon, and near Proctor Valley Road. An old biological survey report notes this shrub in San Elijo Canyon southwest of Harmony Grove The species' range is primarily west of Interstate 15 and south of Highway 78.
Thirty-one Baja California collections in the San Diego Herbarium indicate a considerable range and distribution. It was collected as far south as 28 17' North by Moran (SD 54071) in a canyon east of Gill Peak on Cedros Island. San Diego Marsh Elder is common in a drainage several miles east of Rodriguez Dam in Baja California on the highway to Tecate, Mexico.
Status: San Diego Marsh Elder is considered stable but potentially affected by modifications and degradation of coastal drainages in San Diego County. It is a rather aggressive shrub which could expand its range if introduced into coastal creeks where it is not presently found. Substantial portions of sizeable populations should be protected.
Copyright © May 1994 Craig H. Reiser.
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