Rue, scientifically known as Ruta graveolens, is a perennial subshrub native to the Mediterranean region. Often called herb-of-grace, it is cultivated globally for its ornamental qualities and historical applications. Identifying Rue involves recognizing its distinctive structure, unusual foliage color, and specific flower characteristics. Understanding its physical attributes is the first step in proper identification.
Overall Physical Appearance and Structure
Rue establishes itself as a small, bushy, and woody subshrub, typically reaching a height and spread of between two and three feet. Its overall silhouette is compact and somewhat rounded, making it a popular choice for low hedges or border planting.
The stems of Ruta graveolens begin as soft, pale green growth but quickly become woody with age. This structural woodiness allows the plant to maintain its form and remain evergreen in warmer climates. Gardeners often prune the plant back to the older, woody portions in the early spring to promote bushier growth.
The Distinctive Foliage and Flowers
The foliage possesses an unusual blue-green or glaucous coloration. These leaves are highly segmented, displaying a compound structure that is typically two to three times divided, giving them a delicate, feathery appearance. Each leaflet is oblong and rounded, and the entire leaf surface is gland-dotted, which is a feature of the Rutaceae family.
The presence of these glands is responsible for the plant’s strong, pungent odor, released when the leaves are bruised or handled. This aroma contributed to its historical use as a natural insect repellent.
During the summer, the plant produces small, dull yellow flowers held in clusters called cymes at the tips of the stems. These flowers contrast sharply with the blue-green foliage. Rue flowers usually have four petals, though the central flower often exhibits five. After pollination, the flowers are followed by small, lobed, brown seed capsules containing numerous seeds.
Crucial Identification Warning: Handling and Skin Sensitivity
A serious consideration for identifying and interacting with Rue is its potential to cause a severe skin reaction known as phytophotodermatitis. The herb contains natural chemical compounds called furanocoumarins, which are potent photosensitizers present throughout the plant.
If the sap or crushed foliage comes into contact with the skin and is subsequently exposed to ultraviolet light from the sun, a non-immunologic reaction occurs. The furanocoumarins absorb the UV radiation, leading to a toxic reaction in the skin cells. This results in symptoms that can range from a severe rash and intense burning to painful blistering and temporary hyperpigmentation.
The reaction can sometimes manifest as second-degree burn-like wounds. Due to this phototoxic risk, it is strongly recommended to wear protective clothing, such as long sleeves and gloves, when pruning or handling the plant.