Boxthorn (Lycium) is a genus of the nightshade family (Solanaceae), containing about 90 species of plants native throughout much of the temperate and subtropical zones of the world. They are mostly found in dry, semi-saline environments.
Other common names include desert-thorn, Christmas berry, wolfberry, Matrimony vine, and the confusing "Tea-tree" (it is not related to tea or the Melaleuca tea trees, and with Lycium foliage being toxic, should not be used as such). Goji is a common English name made popular by several American-made juices and dried berries sometimes branded as "Tibetan" or "Himalayan" goji berries, although these terms do not geographically represent where the berries actually originate.
There are ~20 species in North America, ~30 species in South America, ~30 species in Africa, ~10 species in Eurasia, and one species in Australia. Grabowskia and Phrodus join Lycium in the tribe Lycieae, and are the genera most closely related to boxthorn.
They are long-lived, perennial, thorny shrubs, with deciduous alternate, simple leaves 1-8 cm long. The flowers are solitary or in small clusters, 6-25 mm diameter, with a corolla of five purple, white or greenish-white petals joined together at their bases. The fruit is fleshy, multiseeded berry 8-20 mm diameter that may be red, yellow, orange, purple or black. These fruit resemble nightshade and bittersweet berries. In some species called wolfberries or "longevity fruit" (notably L. barbarum and L. chinense), the fruit is edible.
Most species of Lycium are cosexual (all flowers have both male and female function), however, several species exhibit sexual dimorphism. Evidence suggests that sexual dimorphism has evolved more than once in the genus. There are species that have both monecious and dioceous populations, most notably L. californicum.
Boxthorn is mentioned in the biblical Book of Proverbs as besetting the paths of the wicked (). In his 1753 publication Species Plantarum, Linnaeus describes three Lycium species: L. afrum, L. barbarum, and L. europaeum.
The fruit, leaves, and bark of certain species have been used in China throughout more than 2,000 years of recorded history. Wolfberries are known in China as gǒu qǐ zǐ (枸杞子), and are processed into herbal teas, soups, juices, and alcoholic beverages. The bark is also used, it is known in Chinese as dì gǔ pí (地骨皮).
The berries may also be used whole; in traditional Chinese medicine they are always cooked, boiled either by themselves or in combination with other herbs; or as an ingredient in a soup. Whole wolfberries are used in this way for a variety of purposes in traditional Korean medicine and traditional Tibetan medicine, where boxthorn is called dre-tsher-ma ("ghost thorn"). It is a rare ingredient in kampō (traditional Japanese medicine), where the fruit is called kukoshi (クコシ) and the bark jikoppi (ジコッピ); these terms are derived from the Chinese names.
The berry has a complex, rich nutrient and phytochemical profile among which its active ingredients include multiple essential vitamins, minerals, sources of dietary fiber, protein and numerous carotenoids, polyphenols, and polysaccharides. Boxdorn preparations are considered an adaptogen and wolfberries are a possible "superfruit" with high health and commercial value.
"Lycium eleagnus", "Lycium eleganus" and "Lycium eleganus barbarum" are obsolete or invented names often used to promote "authentic" "Tibetan goji". Lycium foetidum and L. japonicum are junior synonyms of Serissa foetida = S. japonica.