White Fiesta Flower

There are two spring-blooming, sprawling plants of shady or moist places with very small flowers and the same two common names: white fiesta flower, Pholistoma racemosum (also called San Diego fiesta flower) and San Diego fiesta flower, P. membranaceum (also called white fiesta flower). These plants are similar and easily confused. In addition, common eucrypta (Eucrypta chrysanthemifolia) shares many of the obvious characteristics, and purple-flowering fiesta flower, when not in bloom, is similar to the San Diego fiesta flower.

A quick way to distinguish these is by means of their mature foliage. The white fiesta flower (upper right) is pinnately lobed into broad lobes, which may, in turn, have a few secondary lobes or large scallops. In contrast, the San Diego fiesta flower(upper left) and the fiesta flower (lower left) have leaves that are deeply, pinnately lobed into narrowly lanceolate segments.

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 fourth 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.

Description ^2,4,59

White fiesta flower is a sprawling annual herb, often leaning on adjacent vegetation for support, reaching two feet in height on weak, brittle, many-branched stems. Leaves are opposite or alternate along the stems, on narrow-winged petioles that partially clasp the stem. Blades are ovate to triangular, 1-3 inches long (2.5-8.0 cm) and nearly as broad; leaves pinnately divided into 3-9 lobes that may themselves have a few broad, shallow secondary lobes. Upper leaves are gradually reduced in size often to three lobes. Both stems and leaves have hairs and sharp, recurved prickles.

Flowers are solitary or a few in loose clusters, blooming sequentially from the top. They are bisexual, radial and five-parted, less than 1/4 inch (0.5 cm) across. The bristly sepals are fused into a five-lobed calyx. Between each pair of lobes is a small appendix extending outward; these are formed from an outward fold of the calyx.

The five-lobed corolla is usually white. There is a single globose ovary with a small, two branched style. The ovary is surrounded by a pale green nectary disc. The five stamens do not extend beyond the corolla. Flowers bloom from Feb.to May.⁴⁶⁸

The fruit is a dry, globose capsule, dark purple partially surrounded by the prickly calyx. When dry, the capsule splits open by two valves to release a few tiny, ovoid brown seeds that are strongly honeycombed.

Classification ^2,59  

White  fiesta flower is a dicot angiosperm in the borage family (Boraginaceae).² Plants in the borage family are coated by small, stiff hairs, and have flowers that are often 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 similar morphological characteristics. Recently, 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 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. membranaceum.

Ecology

We have found no literature reports of ecological adaptations of white fiesta flower. However, it seems reasonable to assume that the strong, downward-directed prickles on stems and leaves provide the same clinging-climbing ability as do those of the related fiesta flower (P. auritum). Since the plant lacks methods for twining or adhering, these prickles allow it to gain purchase on neighboring structures and grow into the less shaded layers above.⁴⁶⁸

Human Uses

We have found no reports of uses either in the past or the present.

Interesting Facts ⁵⁹

The specific scientific name, racemosum, refers to the structure of the flower cluster and is derived from the Latin word “racemulus” which means the stalk of a bunch of grapes.