San Diego Fiesta Flower

Pholistoma membranaceum

leaves of four related species
Leaves of four related species | Central Basin, south side | March 2020

There are three spring blooming low-mounding plants in shady or moist areas with very small, white flowers: San Diego fiesta flower (Pholistoma membranaceum), white fiesta flower (Pholistoma racemosum) and common eucrypta (Eucrypta chrysanthemifolia). These are superficially similar and easily confused. In addition, unless showy its blue-purple flowers are present, a third fiesta flower (Pholistoma auritum) is similar to San Diego fiesta flower. Complicating things is the fact that San Diego fiesta flower and white fiesta flower share both common names while the more showy plant is usually called just fiesta flower.

The easiest way to distinguish these is by means of their leaves. The San Diego fiesta flower (upper left) and fiesta flower (lower left) have leaves that are deeply, pinnately lobed into narrow segments. The petiole of the purple-flowering fiesta flower has a broad wing; that of the San Diego fiesta flower is much narrower, if noticeable at all.

In contrast, the leaf of the white fiesta flower (upper right) is pinnately divided into much broader lobes, which may, in turn, have a few secondary lobes or large scallops. All Pholistoma species are weak, vining herbs that have downward-pointing hairs that help them grab onto surrounding surfaces and often feel like Velcro©.

The final plant, common eucrypta (lower right) is a small sub-shrub. Its leaves are more finely divided; the primary lobes have secondary lobes and even tertiary lobes or scallops. Common eucrypta lacks the hairs that give the others their grabby feeling.

Other Common Names:

white fiesta flower

Description 2,26,290,468

San Diego fiesta flower is a sprawling annual herb, often leaning on adjacent vegetation for support. The weak stems are brittle and many-branched reaching three feet (90 cm) in length. Petioles have narrow wings. The bluish-green leaves range in length from less than one to five inches (2-13 cm) long. They are ovate to oblong and deeply pinnately divided usually into 5-11 narrow lobes. The lobes may have one or two small secondary lobes but otherwise have smooth margins. Lobes are somewhat downward directed, giving the leaf the look of a stylized Christmas tree. Upper leaves are gradually reduced in size sometimes to three lobes. Stems have small scattered recurved hairs; there are fewer if any on the leaves.

Flowers occur in loose uncoiling clusters, with one or a few blooms open at the top of the coil. They are bisexual, radial and five-parted, less than 1/3 inch (1 cm) across. Sepals are fused into a calyx with five rounded lobes. (Unlike other fiesta flowers, San Diego fiesta flower lacks small appendages between calyx lobes.) The five-lobed corolla is white; there are reports of a purple line or spot on each lobe(2,270), but these are rare in our material; however, we do see small dark purple spots on the calyx and the ovary, as well as faint streaks on the stems.

There is a single superior, ovoid ovary with a small, two branched style. The ovary is surrounded by a pale green nectary disc. The five stamens are attached to the corolla tube between the lobes and do not extend beyond the corolla. The anthers are blue-purple, fading to tan or brown; the pollen is white. Flowers bloom from Feb.to May.468

The fruit is a dark purple, dry capsule, which is globose, prickly, occasionally tubercled. When dry, the capsule splits open by two valves to release one or two tiny, ovoid brown seeds.

deeply cut leaves look like styalized Christmas trees

Leaves are deeply lobed | Central Basin, south side | March 2019

small white flower with five petals

Central Basin, south side | April 2018

dark purple, spiny round fruit

Ripe fruit | Central Basin, south side | May 2019

Distribution 4,7,89  

San Diego fiesta flower is native to mainland California, south of San Francisco Bay, below 3500 feet, and to limited areas in northwestern Nevada and northern Baja. It prefers shady areas in a variety of vegetation types, including chaparral and oak and Joshua tree woodlands. There are relatively few observations from coastal California, west of the Coastal Ranges, which is the area preferred by the congeneric species, white fiesta flower (P. racemosum).

There is one stand of San Diego fiesta flower easily seen from the Reserve trails. This is on the south side of the Central Basin at the juncture of the main east-west trail and the eastern end of the Gemma Parks loop trail

Classification 2,59,310    

San Diego fiesta flower is a dicot angiosperm in the borage family (Boraginaceae).2 Typically, plants in the borage family are covered with small, stiff hairs, and have flowers that are located along a coiled stalk.

Perhaps the best-known members of the Boraginaceae are the garden forget-me-not and borage, an annual herb native to Europe and Asia that is used in soups and salads.41 Other plants in the borage family that are found in the Reserve include common phacelia (Phacelia distans), coast fiddleneck (Amsinkia intermedia) and common cryptantha (Cryptantha intermedia).48

Species of Pholistoma were previously placed in the waterleaf family (Hydrophyllaceae), based on morphological characteristics. Subsequently, the availability of molecular data has led to several reinterpretations of these plants including the merging of the waterleaf family into the borage family. This is the system currently used by Jepson,2 the authority for this Plant Guide. In 2016, the Boraginales Working Group re-evaluated the borage complex and recommended a separate waterleaf family.422 Many botanists have accepted this revision and Pholistoma is found listed in the Hydrophyllaceae in both the oldest and most recent literature. Research into the relationships between the two families is continuing and the systematics still evolving.

The genus Pholistoma is a small genus with just three species. All three occur in the Reserve; the other two are fiesta flower, P. auritum and white fiesta flower, P. racemosum.

Jepson eFlora Taxon Page
small prickles on stem

Larger, hairs along stem are recurved | Central Basin, south side | April 2019

small white flowers

Flowers produced from coiled stems | Central Basin, south side | April 2011

a sprinkle of small white flowers

Plants lean on surrounding vegetation | Central Basin, south side | April 2018


Plant ecologists believe that the main function of the hairs on the foliage of the three fiesta flowers is primarily as an aid to climbing.59 However, plant hairs as a whole have been implicated in a number of adaptive functions, including insect deterrence, sun and wind protection41 and fog capture.41,513
There is no way to know if climbing is the only, or even the primary benefit of fiesta flower hairs

fine and coarse hairs on stem

Grazing deterrent? | Central Basin, south side | April 2019

white flower covered with dew

Fog-catcher? | Central Basin, south side | March 2019

round dried fruits splitting open

Dried fruits splitting to release seeds | Central Basin, south side | March 2020

Human Uses 282

The Tubatulabal Indians of the Kern River Valley in the Sierra Nevadas used the leaves as food. These were rolled in their hands with salt grass and eaten.

Interesting Facts 291

The species name, membranaceum, comes from the Latin word “membrana” and the Middle French word “membraneaux” meaning a skin or parchment. It is not clear why it was applied to this plant – perhaps in reference to the narrow wing of the petiole.