White fiesta flower (Pholistoma membranaceum) is one of three related plants with weak, sprawling stems and small white flowers. The others are San Diego fiesta flower (P. racemosum) and common Eucrypta (Eucrypta chrysanthemifolia). They like shady areas and are often found along the trails, climbing out from shrubs of the sage scrub, using their branches for support. All have small white flowers that play peek-a-boo from gaps in the surrounding foliage. All are easy to miss.
White Fiesta Flower
Pholistoma membranaceum
Other Common Names:
San Diego fiesta flower
Description 2,26,290,468
White 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, white 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.
Distribution 4,7,89
White 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, San Diego fiesta flower (P. racemosum).
There is one patch of white 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
Learn more about plant vegetation types here
Classification 2,59,310
White fiesta flower (Pholistoma membranaceum) is a dicot angiosperm characterized by small, stiff hairs and flowers that are often located along a coiled stalk.
Originally, species of Pholistoma were placed in the waterleaf family (Hydrophyllaceae), based on similar morphological characteristics. More recently, the availability of molecular data led to several reinterpretations of these plants including the merging of the waterleaf family into the borage family (Boraginaceae). In 2016, the Boraginales Working Group re-evaluated the borage complex and again 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 is 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 San Diego fiesta flower, P. racemosum.
Jepson eFlora Taxon Page
Ecology
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
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.
