California Box Thorn

Lycium californicum

California box thorn (Lycium californicum) is a succulent shrub of coastal bluffs in southwestern California and northern Baja California. Desert populations occur in Arizona and northern Mexico. Our box thorn has small white flowers followed by attractive red berries.

The berries of California box thorn are said to be edible but often insipid and bitter. They are related to goji berries, which are the fruit of Asian box thorns and which have a long history of use as medicines and health foods.

Other Common Names:

Box thorn, California desert thorn, California wolfberry

Description

California box thorn is a low, dense shrub, usually less than 6 feet in height, with stiff branches and sharply-pointed twigs. Leaves are smooth, bright green and succulent, with short, indistinct petioles. Leaves are linear to oblanceolate, nearly round in cross-section and up to 1/2 inch (1 cm) long,  They may be dropped during drought.

The small flowers are bisexual and radially symmetrical, about 1/4 inch (.65 cm) across. The flower parts are in four’s; the calyx has four green lobes and the corolla has four lobes, which  are white with pale purple lines, fading to tan as flower ages. Lobes flare outward. There are four stamens that extend somewhat beyond the corolla and have tufts of hair from the lower filaments; these fill the corolla throat and are difficult to see. The single pistil has a superior, green, two-chambered ovary and a white style with a capitate stigma that extends about level with the anthers. A nectary surrounds the lower portion of the ovary. California box thorn usually blooms from March into July,468 earlier with early rains.

The fruit is a pretty red, two-seeded berry, obovate to nearly spherical in shape, about 1/4 inch (0.65 cm) long, with a small indentation at the top.

Distribution

California box thorn is native to southern California and northern Baja California and Mexico, extending east into Arizona. It can be common in coastal sage scrub on coastal bluffs, but also in low, sparse, saline desert areas.400

In California it is found below 525 feet (160 m) near the immediate coast from Orange Co south and on the Channel Islands; there are two isolated inland populations in Riverside and San Bernardino Counties. It prefers rocky flats and coastal bluffs.

Only a few specimens are visible from the trails in the Reserve. These can be seen spilling down the bluff between Manchester Ave and the Nature Center, where they may have been planted. A few years ago, a larger, upright shrub grew on the west side of the railroad berm in East Basin. This may not have survived the railroad construction in 2017-19.

California box thorn has been given a California Rare Plant Rank of 4.2 because of its limited distribution in California which is threatened by development, foot traffic and trail maintenance.45

Classification

California box thorn is a dicot angiosperm in the Solanaceae (tobacco or nightshade or potato family). Members of this family typically have five petals that are fused into a tube, at least at the base and five stamens. Sometimes the petals or lobes are reflexed. Fruits are either a berry or a capsule.  Many members of this family contain alkaloid compounds which may be toxic or narcotic; these include scopolamine, atropine and nicotine.

The tobacco family includes many well-known food and ornamental species such as tomato, pepper, potato, petunia and night-blooming jasmine. The family also includes tobacco and belladonna.

As of 2019, eight species in this family have been reported from the Reserve48  including  Parish’s nightshade (Solanum parishii),sacred datura (Datura wrightii) and the invasive tree tobacco (Nicotiana glauca).

Within this family, Lyceum is recognized by the shrubby, spiny growth form and by characteristics of the flower and fruit. SomeLycium species, including California box thorn differ from the typical tobacco family profile by having flower parts mostly in fours, not fives.

Ecology

The fine hairs produced from the lower portions of a flower’s filaments fill the corolla throat, seemingly blocking access to the nectar glands around the base of the ovary, making a key pollinator attractant inaccessible.  Do these hairs restrict access to very small pollinators? to very large pollinators? to pollinators with long tongues? Do they restrict pollinators at all? Perhaps they somehow wick the nectar outward. Perhaps they are residual echoes of conditions past and developed in response to ecological pressures that no longer exist.  What do you think?

Human Uses

Berries of all the western species of Lycium are said to be edible although some species taste better than others.34 Native Americans used the berries of several species as food;282 they were sometimes eaten fresh but most often they were boiled or dried for future use. The berries of California box thorn are reported to be somewhat tasteless and slightly bitter.34

Interesting Facts

Goji berries have recently joined the U.S. health food ranks as a Superfood. What is a goji berry? It is one of two closely realted species, Lycium barbarum and L. chinensis,  Asian cousins of the California box thorn.

In Asia, these little red berries have been eaten for centuries in hopes of living longer. Recently, they have been tried as treatments for diabetes, fever and high blood pressure and for inducing better sleep, weight loss, athletic performance and overall calmness and feeling of well-being. As of 2018, clinical evidence for these benefits is lacking, but goji berries do contain high levels of phytochemicals such as polysaccarides (an important source of dietary fiber), beta-carotene (important for cell development and health of eyes, bones and skin) and zeazanthin (important for the immune system and implicated in the prevention of macular digeneration).