Coastal dunes are scattered along the coast from the Oregon border to San Diego. They are dynamic habitats that are affected by wave action, tides, and especially wind. Dunes develop where there is a substantial amount of dry, wind-blown sand. Foredunes are closer to the sea, and are more dynamic, while backdunes, set off the immediate coast, are more stabilized. Plants found in dunes are often prostrate (lowlying or mat forming) herbs with long taproots and can have creeping stems. Their leaves are often small, fleshy and succulent, and sometimes covered in fine hairs or light in color. These are all adaptations to excessive blowing sand and intense sunlight, typical of these harsh environments. Southern California coastal sand dunes support the endangered globose dune beetle and California legless lizard. Dunes have been greatly diminished by development, agriculture, off-road vehicle use, and invasive plant species.
Red sand verbena
| Abronia maritima | Nyctaginaceae (four o’clock family) |
Prostrate perennial, stems 0.2-1 m (8-40 in), with thick succulent leaves and reddish to magenta flowers. Grows on stabilized dunes along the coast. CNPS gives it a 4.2 rarity rating for its limited distribution, which is the southern portion of the state into Baja. Its soft, rubbery texture gives no protection against beach goers, and it is easily affected by tram- pling. They are self-sterile, meaning they must cross pollinate to produce seeds, and most fruits do not contain seeds.
The shrinking of beaches due to rising seas is eroding the habitat of these and other dune plants because dune habitats cannot move inland, such as along bluffs or development.
Pink sand verbena
| Abronia umbellata | Nyctaginaceae (four o’clock family) |
Prostrate perennial, stems 0.2-1 m (8-40 in), with thick succulent leaves and whitish-pink flowers. This species is often found locally growing with A. maritima, and has a broader range, extending farther up the central and north coast of California than does A. maritima.
Beach-bur
| Ambrosia cham issonis | Asteraceae (sunflower family) |
Prostrate perennial herb forming a mat or mound, up to 3 m (10 ft) wide and 0.3 m (1 ft) high, with grayish-silver foliage and spiny fruits. The inflorescence (flower) is composed of separate male and female flowers. The male flower is yellowish-green and the female flower, found below the male, is whitish-green. This is often the only remaining native plant on dunes that are heavily recreated on, as its spiny fruits deter bare feet and sunbathing.
As with most dune plants, the sand and leaf litter beneath the spreading plants is often rich with invertebrate (insect) diversity.
Beach saltbush
| Atriplex leucophylla | Chenopodiaceae (goosefoot family) |
Prostrate perennial herb, stems 30-50 cm (12-18 in) long, with whitish foliage. Atriplex species tolerate salty soils by removing excess salt through glands on the leaf surfaces. Atriplex leucophylla grows on foredunes closer to the ocean than most other species, and is not found on more stabilized backdunes as frequently. Consequently, it is often inundated or uprooted by king tides or slough breaches. The species name leucophylla refers to the light, whitish color of its leaves.
Beach primrose
| Camissoniopsis cheiranthifolia | Onagraceae (primrose family) |
Prostrate perennial, stems to 60 cm (24 in), with light greenish-gray leaves and striking yellow flowers that fade to reddish-orange. The fruits are coiled capsules. Several other species of primroses occur locally, including the diminutive Camissoniopsis micrantha and the showy, erect Camissoniopsis elata ssp hookeri, whose nutritious seeds feed migrating songbirds.