Ruta graveolens Seeds | Rue
LATIN NAME: Ruta graveolens
COMMON NAME: Rue
Plant Profile
Rue is the shrubby, blue-green perennial of old cottage gardens, with finely divided, somewhat succulent leaves that carry a strong, bitter, resinous scent unlike anything in the mint bed. Its claim to caution is chemical: the foliage contains furanocoumarins, chiefly psoralen and related compounds, that make the sap phototoxic. Brushed on bare skin and then exposed to bright sun, the oil can cause a rash and lingering marks, which is why seasoned gardeners handle rue with gloves and avoid crushing it in hot sun. The flowers are an unusual sulphur-yellow, four-petalled, and carried in loose terminal clusters, followed by lobed capsule fruits that split to show the seeds.
Rue is a member of the citrus family, a kinship visible in the pungent oil glands dotted along the leaf, and it differs from the soft herbaceous mints by being a semi-woody, longer-lived sub-shrub that holds its form through the year in mild climates. That woody habit is why it earns a place at the back of a herb border where the mints would flop, and why a single plant can persist and slowly broaden for several seasons.
Science & Biotechnology
The leaf essential oil is rich in methyl nonyl ketone (also called 2-undecanone) and carries the furanocoumarins mentioned above, plus smaller rutaceous alkaloids. The same furanocoumarins are why rue extract appears in studied, highly regulated contexts such as plant-derived psoralen used in dermatology under controlled conditions, rather than as a kitchen herb in quantity. Traditional European use of rue as a culinary flavouring was always sparing because of the bitterness and the skin sensitivity, and modern formulators treat the plant with respect rather than as a routine ingredient.
On the research side, rue has been screened for its antimicrobial and insect-repellent properties, and the furanocoumarin pathway has been a model for studying plant chemical defence. Tissue-culture multiplication of selected blue-leaved forms is documented, letting growers keep a uniform, non-segregating ornamental line, and the chemistry helps explain why few herbivores browse the foliage.
Uses & Benefits
In the garden rue is grown for its colour and architecture: the silvery blue mound makes a fine edging against brick or warm stone, and ‘Jackman’s Blue’ is the standard for that effect. A few leaves were traditionally added to strong cheeses, grappa, and bitters, and the flower heads dry for arrangements, but the flavour is powerful and the skin risk real, so most modern cooks admire rue more than they eat it. It also has a long symbolic history in European gardens as the herb of grace, planted near doorways in older cottage layouts.
Rue was valued by the Romans and is discussed at length by Pliny, and in later centuries it was planted in knot gardens and used as a strewing herb for its strong scent. Its bitterness kept it a symbolic and medicinal plant more than a food, and the phototoxic sap is the reason modern handling stays cautious; the blue foliage remains the safest and most rewarding part to enjoy. In the kitchen a single leaf flavours a jar of pickled beans or a bottle of grappa, and the blue form is the one to grow for ornament, since rue also does well in a container where its spread stays contained and the gloves stay close at hand.
Growing from Seed
Sow the seed on the surface of a free-draining seed compost and press it in lightly, as light helps it start, then keep the medium just damp. Transplant or thin seedlings once they reach four to six true leaves, setting plants about 35 to 45 cm apart in a row so the mounds have room to spread. Rue wants full sun and a sharp, well-drained soil; it thrives on poor, rocky, alkaline ground and resents rich, wet earth where the base can rot. Water young plants to establish them, then cut back sharply because established rue is drought tolerant. Trim the plant back in early spring to keep it compact, and wear gloves when cutting because the sap can mark skin in sun. Propagate choice forms by heel cuttings or division rather than by seed to keep the blue colour true, and avoid seating yourself among the plants on a hot, bright afternoon.
Our Take
Rue is a look-don’t-touch plant in my garden: glorious blue foliage, gloves on for any pruning. For other strongly scented, sun-loving herbs see English Sage, Syrian Rue, and Sweet Annie.
Related Reading
More species in the same orbit as Rue: