Silphium

It was an essential item of trade from the ancient North African city of Cyrene, and was so critical to the Cyrenian economy that most of their coins bore an image of the plant. The valuable product was the plant's resin, called in Latin laserpicium, lasarpicium, or laser (Laserpitium and Laser were used by botanists to name genera of aromatic plants, but the silphium plant is not believed to belong to these genera).

The exact identity of silphium is unclear. It was claimed to have become extinct in Roman times, but is commonly believed to have been a relative of giant fennel in the genus Ferula. The extant plant Thapsia gummifera has been suggested as another possibility. Another conjecture is that it was simply a high-quality variety of asafoetida, a common seasoning in the Roman Empire, for the two were considered the same by many Romans, including the geographer Strabo.

Silphium was considered highly valuable by all who held it. The plant was sung about by Roman poets and singers, who considered it equivalent to its weight in gold. Historically, Pliny the Elder blamed silphium's valuation on "tax-farmers", and Julius Caesar directly registered silphium as "1500 pounds of laser" in the Roman treasury.

Identity and extinction

The identity of silphium is highly debated. Without a surviving sample, no genetic analysis can be made. It is generally considered to belong to the genera Ferula or Thapsia as an extinct or living species. The extant plants Ferula tingitana, Ferula narthex, Ferula drudeana, Thapsia gummifera, and Thapsia garganica have been suggested as possible matches. Ferula drudeana, an endemic species found in Turkey, is considered a strong candidate for silphium based on several unusual shared features, such as the plant morphology, yellow foliage of mature plants, slow growth, resistance to cultivation from seed, and phytochemistry, including its production of an aromatic, spice-like gum resin with properties similar to those reported for silphium. However, F. drudeana belongs to a lineage from the southern Caspian Sea region with no known connection to eastern Libya. This species is also considered highly imperiled, with few surviving populations, and threats posed by overharvesting for use as an aphrodisiac.

Theophrastus mentioned silphium as having thick roots covered in black bark, about one cubit (48 cm) long, with a hollow stalk, similar to fennel, and golden leaves like those of celery.

The disappearance of silphium has been suggested to be the first extinction of a plant or animal species in recorded history. The cause of silphium's supposed extinction is not entirely known, but numerous factors are suggested. Silphium had a remarkably narrow native range, about 125 by 35 miles (201 by 56 km), in the southern steppe of Cyrenaica (present-day eastern Libya). Overgrazing combined with overharvesting have long been cited as the primary factors that led to its extinction. Recent research has challenged this notion, though, arguing instead that desertification in ancient Cyrenaica was the primary driver of silphium's decline.

Another theory is that when Roman provincial governors took over from Greek colonists, they overfarmed silphium and rendered the soil unable to yield the type that was said to be of such medicinal value. Theophrastus wrote in Enquiry into Plants that the type of Ferula specifically referred to as "silphium" was odd in that it could not be cultivated. He reports inconsistencies in the information he received about this, however. This could suggest the plant is similarly sensitive to soil chemistry as huckleberries, which when grown from seed, are devoid of fruit.

Similar to the soil theory, another theory holds that the plant was a hybrid, which often results in very desired traits in the first generation, but hybrids are often sterile, so it is possible that silphium could not be propagated from seeds at all (which would indeed make cultivation considerably more difficult), but instead only asexually through their roots.

Pliny reported that the last known stalk of silphium found in Cyrenaica was given to Emperor Nero "as a curiosity".