Rue (Ruta graveolens)

Common Rue, Garden Rue, Herb of Grace, Rue

Rue – Ruta graveolens is a beautiful, undemanding and evergreen perennial with lots of health benefits. As early as the Roman Empire and throughout the Middle Ages, rue (Ruta graveolens) was a popular spice and, most importantly, a common medicinal herb. Some traditional rue recipes from these times have even been preserved. Nowadays, rue is mainly cultivated as an ingredient used in grappa (a kind of liqueur), as well as a heat and drought tolerant aromatic herb and as a decorative perennial in home gardens.

I. Appearance and Characteristics 

Ruta graveolens, commonly known as rue, common rue or herb-of-grace, is a species of the genus Ruta grown as an ornamental plant and herb. It is native to the Balkan Peninsula. It is grown throughout the world in gardens, especially for its bluish leaves, and sometimes for its tolerance of hot and dry soil conditions. It is also cultivated as a culinary herb, and to a lesser extent as an insect repellent and incense.

The specific epithet graveolens refers to the strong-smelling leaves.

Rue is a woody, perennial shrub. Its leaves are oblong, blue green and arranged pinnate; they release a strong aroma when they are bruised.

The flowers are small with 4 to 5 dull yellow petals in clusters. They bear brown seed capsules when pollinated.

Rue is generally safe if consumed in small amounts as an herb to flavor food. Rue extracts are mutagenic and hepatotoxic. Large doses can cause violent gastric pain, vomiting, liver damage, and death. This is due to a variety of toxic compounds in the plant’s sap. It is recommended to only use small amounts in food, and to not consume it excessively. It should be strictly avoided by pregnant women, as it can be an abortifacient and teratogen.

Exposure to common rue, or herbal preparations derived from it, can cause severe phytophotodermatitis, which results in burn-like blisters on the skin. The mechanism of action is currently unknown.

II. How to Grow and Care

Sunlight

Rue grows best in full sun, meaning at least six hours of direct sunlight on most days. But partial shade is also tolerated. However, plants will produce fewer flowers in the shade.

Temperature and Humidity

Rue plants thrive in hot weather and low humidity, similar to their native habitat of Greece, Turkey, and Italy. However, the plants are tolerant of humidity as long as they have good soil drainage and air circulation around them.

Watering

Once established, common rue is very drought tolerant and is a good candidate for a xeriscape or rock garden. You won’t need to water except for periods of extensive dry weather. Avoid overwatering, which can cause root rot.

Soil

Sharp drainage is important for healthy rue plants. Add sand, perlite, or vermiculite to the soil to help drainage. Or use raised beds with prepared soil in gardens where heavy clay dominates. Rue likes a moderately rich soil but can tolerate poor soils. And it can grow in a slightly acidic to slightly alkaline soil pH.

Fertilizing

Do not fertilize rue plants. Excess nutrients will cause the plants to produce more foliage at the expense of the flowers.

Pruning

Rue is a semi-woody perennial that flowers on new growth. To keep the plant vigorous and looking its best, cut stems back to around 6 inches in the early spring. Don’t wait too long, or you’ll end up pruning off some flower buds. You also can prune in the fall after flowering is finished.

Propagation

It’s easy to make new rue plants via stem cuttings. This is a quick and inexpensive way to replace mature plants that are nearing the end of their life cycle, as rue plants only live around five years. The best time to take cuttings is in the late summer from new growth, but be sure to wear protective clothing during the process. Here’s how:

  • Cut roughly a 6-inch piece of stem from new growth.
  • Remove any foliage on the lower half of the cutting.
  • Plant the cutting in a container of moistened soilless potting mix.
  • Place in a clear bag to maintain moisture.
  • Keep the mix moist but not soggy. Once you feel resistance when you gently tug on the stem, you’ll know roots have developed.

How to Grow fFrom Seed

Rue is easy to start from seeds in the garden or in trays. The soil must be at least 68 degrees Fahrenheit for germination, and some light must reach the seeds. When the seedlings develop at least two sets of true leaves, they can be transplanted into larger pots. Harden off seedlings before planting in the garden.

Rue plants will self-seed, sometimes aggressively, in warm regions. You can collect the brown seed capsules in late summer after flowering to plant elsewhere.

How to Grow in Pots

If you don’t have garden space or have heavy soil, container growth is a good option for rue. Choose a pot that’s around 12 to 16 inches wide and deep, and make sure it has drainage holes. An unglazed clay container is ideal because it will allow excess soil moisture to escape through its walls.

Pests and Diseases

Rue doesn’t have any major pest or disease issues. In fact, if you see caterpillars feeding on your rue plants, don’t spray them. It’s likely they are swallowtail butterfly caterpillars, which use rue as a host plant and benefit your entire garden. The primary disease issue that can affect rue is root rot from wet soils. So ensure that your plants are never waterlogged.

Potting and Repotting 

You can use any well-draining potting mix for rue in containers. Repotting is necessary when you see roots coming out of the drainage holes of the pot. Remember to wear protective clothing when repotting.

The bluish foliage of rue plants marries well with plants that have golden foliage, such as the gold cultivars of oregano, sage, or thyme. These herbs all like the same sunny, dry conditions and well-drained soil that rue thrives in, so they blend well in mixed containers.

Overwintering

In the northern portion of rue’s growing zones, add a layer of mulch around the plants to protect them over the winter. Aim to do this before frost hits in the fall.

III. Uses and Benefits 

Traditional use

In the ancient Roman world, the naturalists Pedanius Dioscorides and Pliny the Elder recommended that rue be combined with the poisonous shrub oleander to be drunk as an antidote to venomous snake bites.

The refined oil of rue is an emmenagogue and was cited by the Roman historian Pliny the Elder and Soranus as an abortifacient (inducing abortion).

Culinary use

Rue has a culinary use, but since it is bitter and gastric discomfort may be experienced by some individuals, it is used sparingly. Although used more extensively in former times, it is not a herb that is typically found in modern cuisine. Due to small amounts of toxins it contains, it must be used in small amounts, and should be avoided by pregnant women or women who have liver issues.

It has a variety of other culinary uses:

  • It was used extensively in ancient Near Eastern and Roman cuisine (according to Ibn Sayyar al-Warraq and Apicius).
  • Rue is used as a traditional flavouring in Greece and other Mediterranean countries.
  • In Istria (a region spanning Croatia and Slovenia), and in Northern Italy, it is used to give a special flavour to grappa/raki and most of the time a little branch of the plant can be found in the bottle. This is called grappa alla ruta.
  • Seeds can be used for porridge.
  • The bitter leaf can be added to eggs, cheese, fish, or mixed with damson plums and wine to produce a meat sauce.
  • In Italy in Friuli Venezia-Giulia, the young branches of the plant are dipped in a batter, deep-fried in oil, and consumed with salt or sugar. They are also used on their own to aromatise a specific type of omelet.
  • Used in Old World beers as flavoring ingredients.
  • The rue that is widespread in Ethiopian culture is a different species, R. chalapensis.

Other uses

Rue is also grown as an ornamental plant, both as a low hedge and so the leaves can be used in nosegays.

Most cats dislike the smell of it, and it can, therefore, be used as a deterrent to them (see also Plectranthus caninus).

Caterpillars of some subspecies of the butterfly Papilio machaon feed on rue, as well as other plants. The caterpillars of Papilio xuthus also feed readily on it.

Hasidic Jews also were taught that rue should be placed into amulets to protect them from epidemics and plagues. Other Hasidim rely on the works of a famous Baghdadi Kabbalist Yaakov Chaim Sofer who makes mention of the plant “ruda” (רודה) as an effective device against both black magic and the evil eye.

It finds many household uses around the world as well. It is traditionally used in Central Asia as an insect repellent and room deodorizer.

IV. Harvesting and Storage

Rue is often harvested to use as dried flowers. And some people make sachets out of rue and use them to deter pests, including fleas and ants. Wear gloves and long sleeves when working with rue to protect your skin. Cut a mature plant at ground level with pruners. Then, hang it in a dark, dry place to dry until the leaves become brittle. Keep the fully dried rue in an airtight container until you’re ready to use it for sachets or other purposes.

Rue (Ruta graveolens) Details

Common name Common Rue, Garden Rue, Herb of Grace, Rue
Botanical name Ruta graveolens
Plant type Herb
Hardiness zone 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b
Growth rate Medium
Harvest time Fall
Height 2 ft. 0 in. - 3 ft. 0 in.
Width 2 ft. 0 in. - 3 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Gold/Yellow
Leaf color Blue