Ruta graveolens, commonly known as the rue plant, is a highly aromatic, woody perennial herb cultivated since antiquity. It belongs to the Rutaceae family, which also includes citrus fruits, suggesting a potent biochemical profile. Historically, rue was revered as a protective charm and cautiously employed in traditional medicine and cooking. Its intense fragrance and bitter compounds contributed to its long cultural history, but its powerful chemical composition demands modern caution.
Botanical Profile and Key Characteristics
Ruta graveolens is a small, semi-woody shrub that typically grows to a height of about two to three feet. The plant is native to the Mediterranean region, including the Balkan Peninsula, and is characterized by its distinctive blue-green or glaucous foliage. Its compound leaves are feathery and pinnately divided, featuring gland-studded surfaces that release a pungent, strong aroma when bruised or handled.
The plant produces small, dull yellow flowers that bloom in clusters during the early summer months. Rue is remarkably hardy and thrives in full sun and well-drained, moderately dry soils, making it drought tolerant once established. Its ability to tolerate poor conditions contributes to its common presence in gardens. The specific epithet graveolens is a Latin term that translates to “strongly scented,” a direct reference to the plant’s intense odor.
Historical and Traditional Uses
Rue holds a deep cultural history, particularly in ancient European civilizations where it was widely used by the Greeks and Romans as both a medicinal and culinary herb. The plant’s bitter qualities were used sparingly to flavor dishes, and it was a component of a spicy seasoning paste commonly used in Roman cooking. Ancient naturalists even recommended rue as a chief ingredient in mixtures used as antidotes against various poisons.
During the Middle Ages, the herb gained symbolic significance, often associated with protection and purification. It was frequently used as a strewing herb, scattered on floors to ward off diseases, including the plague. The common name “herb-of-grace” arose from the Catholic Church’s practice of using sprigs of rue to sprinkle holy water over parishioners. Today, rue’s culinary use is severely limited due to its intense bitterness, though it remains a characteristic flavoring in the Ethiopian spice blend berbere and is sometimes used to infuse coffee.
Safety Profile and Chemical Hazards
The strong characteristics of the rue plant are directly linked to its complex phytochemistry, which is dominated by furanocoumarins and potent essential oils. Among the most concerning compounds are the furanocoumarins, such as psoralen and xanthotoxin, which are responsible for the plant’s primary external hazard. These chemicals cause a severe skin reaction known as phytophotodermatitis, a phototoxic contact dermatitis.
The reaction occurs when the compounds on the skin are exposed to long-wave ultraviolet light, specifically UVA radiation, leading to an intense photoirritant response. This contact with the plant followed by sun exposure can result in painful, burn-like blisters, redness, and hyperpigmentation that can last for weeks. Even minor contact, such as brushing against the leaves while gardening, can initiate this reaction, making careful handling with gloves and long sleeves necessary.
Internal consumption of rue is highly discouraged due to its systemic toxicity, particularly the concentrated essential oils and alkaloids. Ingesting large doses can lead to severe gastrointestinal distress, including vomiting and hemorrhages. More dangerously, the plant is hepatotoxic, meaning it can cause significant damage to the liver and kidneys.
Rue has a historical reputation for its emmenagogue and abortifacient properties, traditionally used to stimulate menstruation or terminate a pregnancy. This effect is due to chemicals that can stimulate uterine contractions, but using rue for this purpose is extremely dangerous. The dosage required to affect the uterus can easily reach toxic levels, causing severe internal organ damage or death. This makes rue a severe contraindication for pregnant women.