Beach Sand Verbena

In the spring, our few remaining local sand dunes are a mosaic of yellow and purple. The light purple is beach sand verbena (Abronia umbellata). In spite of its name and general appearance, it is not related to the garden verbena, but to the thorny, vibrant symbol of our Spanish heritage – the bougainvillea. Both have eye-catching color and both lack true petals, but beyond that the similarity ends.

Seeds of beach sand verbena were first collected in 1786 by a French expedition charged with continuing the Pacific explorations of Captain Cook. Seeds were shipped back to Europe where they were grown and studied by the pioneer biologist Jean-Baptiste Lemarck. Beach sand verbena is thought to be the very first California flower described scientifically.

The French expedition subsequently vanished in the Pacific.

Description ^{4,23,59,290,306}

Beach sand verbena is a highly variable species, occasionally hybridizing with other Abronia species. The plant is a low growing perennial (sometimes annual) with several stems from a tap root. The plant may be smooth or covered with sticky hairs,²⁹⁰  and often has sand grains stuck to it. The main stems sprawl along the ground for a meter or more, often forked, occasionally buried in sand. Leaves are somewhat thick and fleshy, oval or elliptic in shape with smooth margins, up to  2½ inches (6 cm) long and two inches (5 cm) wide. Leaves are opposite on the stem with the paired leaves of unequal sizes, often held vertically.

The bright flowers occur in globular clusters. There are usually 10 – 30 flowers per cluster originating from a single point (umbels); all flowers open at the same time. Below each cluster are five or six small bracts that are magenta to green in color and covered with sticky glandular hairs. Flowers lack petals and five bright pink to magenta sepals resemble petals and are covered with glandular hairs. Sepals are united at their bases into a long flower tube, flared at the top into five lobes, each lobe usually split into two smaller lobes. The eye of the tube is pale pink or white. The flower is bisexual and about ½ inch (1.3 mm) long. The stamens and pistil are hidden within the flower tube. The stamen filaments are fused to the floral cup for most of their length. Anthers are vivid yellow with bright yellow pollen. The pistil consists of a superior one-chambered ovary, a light-pink brushy style with a slightly wider, whitish stigma that extends only midway up the floral tube.

The plant often dies back during the driest part of the year, but given adequate moisture, leaves and flowers may be found during any season.^1,7

Fruits form loose clusters of one-seeded, dry capsules. Each capsule is surrounded by usually three conspicuous papery brown wings, derived from the base of the floral tube.

Classification ^2,11,143

Beach sand verbena (Abronia umbellata) is a dicot angiosperm in the four-o’clock family (Nyctaginaceae). This is a small family with only six native genera in California.⁷ Members of the four-o’clock family lack petals. The sepals are united into a tube and are often brightly colored, taking the role of petals. In addition, modified leaves, or bracts, are often associated with a flower cluster. The best known member of the four-o’clock family is the ornamental Bougainvillea, in which the bracts are the most showy part of the flower and surround a small, white, calyx.

The genus Abronia has nine species in California. They are set apart from other genera in this family by the linear stigma which does not extend out of the floral tube, and by structural details of the fruit. All Abronia species are associated with  unstable, porous soils, but the habitats range from beach dunes to desert dunes to alpine granite slopes.³⁴⁹  A close relative, Abronia maritima has been planted in the dune plant restoration areas in West Basin and Cardiff Living Shoreline. Commonly called red sand verbena, this plant is classified as a California rare plant because of limited distribution.⁴⁵

Because of the variability of A. umbellata, many subspecies and varieties have been described. At present, only two are recognized.² The species reported in the Reserve is var. umbellata.⁴⁸

Ecology ³⁵⁰

The rather small seeds of beach sand verbena are surrounded by large, elaborate, papery wings, derived from the calyx. These appear to be an adaptation for dispersal by wind, and wind-driven dispersal distances as much as 120 feet (37 meters) have been measured. This ability of the seed to hitch-hike on the omnipresent sea breeze may help explain the persistence of beach sand verbena in sandy environments that are often small, relatively ephemeral and patchily distributed.

Human Uses ²⁸²

The desert sand verbena (A. villosa), which grows to our east, was used medically. The roots of the coastal sand verbena (A. latifolia), which grows north of Point Conception, were used for food. Given how conspicuous beach sand verbena can be, it is surprising that we have found no reports that our local species was used by our local native Americans.

Interesting Facts

Beach sand verbena was the first California plant described by science.^41,59  Seeds were collected from Monterrey in 1786 by the French Compt de La Perouse expedition to continue the Pacific discoveries of Captain James Cook. Fortunately, some of the seed collection was shipped back to France, for the entire expedition was subsequently lost in a shipwreck in the Solomon Islands. The beach sand verbena seeds were grown in Europe and studied and described by the well known French naturalist Jean-Baptiste Lamarck, best known for his theory that acquired traits can be inherited (Lamarckism).⁴¹

In spite of its common name, beach sand verbena is not related to the garden verbena, which is a genus in the family Verbenaceae. The common name comes from their superficial resemblance.²³