Old reports from urban drainages are often either extirpated sites or endangered by peripheral urban impacts including activities such as horse and hiking trails along the canyon bottoms. A recent report comes from the upper reaches of West Sycamore Canyon. Old biological survey reports note populations in Carroll Canyon and Murphy Canyon. No specimens for subspecies viminea are found in the San Diego Herbarium from Baja California. Some of these Baja plants are poorly differentiated from ssp.
Taxonomic work is needed to clarify the range of the various subspecies.
Willowy Monardella is severely declining in total numbers in San Diego County. The sandy embankments in major canyon riparian systems along the coast, which are the primary microhabitat of Willowy Monardella, are rapidly being developed or degraded. Horse and hiking trails are cumulatively quite damaging in some areas. It is seriously endangered throughout most of its range. The CalTrans mitigation site in San Clemente Canyon for plants lost during the expansion of Highway 52 showed virtually all tagged specimens dead when the location was visited in the summer of 1987.