Silvery Phacelia - Center For Plant Conservation
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Plant Profile

Silvery Phacelia (Phacelia argentea)

Phacelia argentea in its native dune habitat. Photo Credit: Ed Guerrant
  • Global Rank: G2 - Imperiled
  • Legal Status: N/A
  • Family: Hydrophyllaceae
  • State: CA, OR
  • Nature Serve ID: 152494
  • Date Inducted in National Collection: 03/14/1986

Silvery phacelia is the only known Phacelia to grow on coastal sand dunes (Rittenhouse 1995). It grows on the immediate coastal dunes from northern Del Norte County in California to southern Coos County in Oregon. Although this seems like a large distribution (it spans 130 miles), not all of this stretch of coast is suitable habitat because much of the coastline is sharp cliffs or rocks, not sand dunes (Rittenhouse 1995). The encroachment of non-native European beachgrass is reducing this habitat even further. The coast of California and Oregon had a dramatically different appearance 150 years ago. Many beaches had no fore-dune, and in areas where dunes formed, they ran perpendicular to the shore (Russo et al. 1988). European beachgrass was introduced in the late 1800's to stabilize the beach sand. It does its job very well, a little too well in fact. European beachgrass outcompetes native vegetation and alters the native dune community by creating steep foredunes as it traps blowing sand. These steep foredunes run parallel to the shore, a stark contrast to the natural state of the dunes (Russo et al. 1988). In areas where European beachgrass is dominant, silvery Phacelia populations are both small and fragmented or totally nonexistent (Rittenhouse 1995). Although there are many known populations of Silvery Phacelia compared to other rare species, the majority of populations are small and separated by great distances. Reports indicate that most appear to be declining in numbers (Rittenhouse 1995).

Where is Silvery Phacelia (Phacelia argentea) located in the wild?


Phacelia argentea grows on unstabilized or semi-stabilized sand dunes, bluffs, and bases of coastal headlands along the northern California and southern Oregon Pacific coast. Plants are found above the high tide level but below 65 ft (20 m) in elevation.


CA, ORCA: Coastal dunes (Del Norte Co.) OR: Coastal dunes (Coos and Curry Co.)

States & Provinces:

Silvery Phacelia can be found in California, Oregon

Which CPC Partners conserve Silvery Phacelia (Phacelia argentea)?

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, Rae Selling Berry Seed Bank & Plant Conservation Program holds 3 accessions of Phacelia argentea in orthodox seed collection. There are as many as 3159 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, Rae Selling Berry Seed Bank & Plant Conservation Program has collected 3 seed accessions of Phacelia argentea from 3 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 4 maternal plants

Nature Serve Biotics
  • 05/02/2017

This species has a relatively low number of element occurrences (33), and a fairly low number of plants (15,000) over a limited range. If not for threats (coastal development, recreation, competition from exotic species), this species would have received a lower ranking (G3).

  • 01/01/2010

Coastal recreation and development (Meinke 1982). Stabilization of dunes by invading European beachgrass (Ammophila arenaria) leading to loss of suitable habitat (Rittenhouse 1995). Off-road vehicle use. Most populations are in areas where off-road

  • 01/01/2010

As of 1995: 28 sites in Oregon with population sizes ranging from 3 individuals to over 2000. Most were under 100, and many on private land had not been inventoried. In California, 5 sites were known, with population sizes of 15; >500; 1000; 2000; and 10,000 individuals (Rittenhouse 1995). As of 2001, 4 known sites in CA were presumed extant according to California Natural Diversity Database. No indication of numbers of individuals (2001).

  • 01/01/2010

Studies were done to determine if insects are required for successful seed set and observation of pollinators. Inflorescences were either bagged before flower opening or not bagged as a control. Bagged inflorescences had 3% seed set while un-bagged inflorescences had 40% seed set. Seed production appears low even in flowers available to pollinators (Rittenhouse, 1993). Germination trials at The Berry Botanic Garden indicate that seeds germinate readily (between 80% and 100%) when subjected to alternating 50/68 F (10/20 C) temperatures, whether cold stratified or not. When subjected to constant 68F (20C) temperatures no seeds germinated. (BBG file).

  • 01/01/2010

A Conservation Strategy was finalized in 1995 for plants found on Bureau of Land Management (BLM) property. It called for surveying of potential habitat, inventorying of known populations, and monitoring to determine population trends. Initial monitoring was conducted in 1995 and 1996 at three sites on BLM land. As of 2001, the sites had not been re-monitored (Brian 2001) Two sites are on land designated as the New River Area of Critical Environmental Concern (ACEC). Seed collected and stored at The Berry Botanic Garden. Wild collected seed from 1984 (one location in Oregon) and 1990 (4 sites in California). Most collections are bulked (seeds from more than one individual). Seeds from garden grown plants has been collected and stored.

  • 01/01/2010

Research life history: life span, time to first flowering, seed production, etc (Rittenhouse 1995). Restrict ORV use of dune habitat Remove European beachgrass from dunes. Use native sand-binders to hold sand in place along roads instead of European beachgrass.

  • 01/01/2010

Seed collections from known wild populations keeping maternal lines separate (1 plant/bag). Determine propagation protocols and reintroduction methods.


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Taxon Phacelia argentea
Authority A. Nels. & J.F. Macbr.
Family Hydrophyllaceae
CPC Number 3339
ITIS 31454
Common Names sand-dune phacelia | silvery phacelia | sanddune phacelia | Sand dune phacelia
Associated Scientific Names Phacelia argentea
Distribution CA, ORCA: Coastal dunes (Del Norte Co.) OR: Coastal dunes (Coos and Curry Co.)
State Rank
State State Rank
California S1
Oregon S2
Ecological Relationships

The roots of silvery Phacelia and other native beach species serve to stabilize the sand substrate. They do not, however, completely stabilize the dunes. In an effort to control the shoreline and prevent sand from encroaching on streets and property, European beachgrass (Ammophila arenaria) was introduced. It is highly effective at stabilizing dunes and trapping sand. When European beachgrass invades, it stabilizes the dunes, making them uninhabitable to the silvery Phacelia (Rittenhouse 1995). The dunes also change shape and orientation when covered by European beachgrass. Little is known about the biology of Phacelia argentea. Life span, time to first flowering and seed production should all be investigated (Rittenhouse 1995). Silvery Phacelia reproduces primarily be seeds, short rhizomes, and spreads by a branched caudex (Rittenhouse 1995). The silvery appearance comes from the tightly appressed hairs on the leaves (Rittenhouse 1995). The hairs may help to keep salt off the surface of the leaves, decrease water loss in the harsh environment, or reflect excess light.Pollination is insect mediated. The primary pollinators appear to be leafcutter bees (Anthidium palliventre), bumblebees (Bombus sp.), and honeybees (Apis melifera). This particular species of leafcutter bee is found only on the coastal dunes ranging from southern California to British Columbia. They seem to utilize the members of the genus Phacelia that occur directly on the coast and slightly inland. The females are the primary pollinators. They spread pollen from flower to flower as they collect it to line their burrows and feed the developing larvae (Rittenhouse 1993). This is a prime example of how our native flora and fauna are interconnected. Destroying one species destroys another. Preserving one species preserves another.


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