Hundreds of years ago, before all things herbal were a trend, people were growing rue as a medicinal plant. This short-lived woody perennial herb is a mysterious species with broad-ranging and seemingly contradictory uses and applications: It has been used both as a witchcraft ingredient and a holy water additive, and it is touted as a flea repellant as well as a desirable seasoning for sausage and fish. But despite its traditional culinary use, it can be a dangerous plant to use for your own homemade preparations; rue can be quite poisonous when eaten in raw form or even when touched.
But even if you don't explore the herbal uses of this strong-smelling plant, you can still appreciate the way its summer blooms draw butterflies and beneficial parasitic wasps to the garden. When not in bloom, the bluish-green fern-like foliage is a handsome asset in the flower and herb garden.
Rue is normally planted from potted nursery starts or from seeds planted in the garden once spring soil temperatures reach 68 degrees Fahrenheit. It germinates in one to four weeks and quickly grows to its mature size as a shrubby plant.
|Botanical Name||Ruta graveolens|
|Common Name||Rue, common rue, herb-of-grace, herby grass|
|Plant Type||Perennial herb|
|Mature Size||2–3 feet tall, similar width|
|Sun Exposure||Full sun (tolerates some shade)|
|Soil Type||Average to poor soil|
|Soil pH||6.5 to 8.5 (slightly acidic to alkaline)|
|Hardiness Zones||4–8 (USDA)|
|Native Area||Southern Europe|
|Toxicity||In raw form, highly toxic to people and animals|
If you choose a sunny site with good drainage for your rue plants, they almost certainly will thrive with virtually no care. Rue flowers are good candidates for tough sites, and will even grow in gravel. If your garden has heavy or wet soil, consider container culture.
These woody perennials should be cut back to old wood in the spring before new growth starts. Although short-lived (about five years is average), rue self-seeds readily, so a patch is generally self-sustaining.
Rue is more often grown as an ornamental plant than in its traditional role as an herb. It is frequently used in borders and screens, or to lure butterflies (especially swallowtails) to the garden. It also has a reputation for repelling cats, so it is sometimes planted for this purpose.
Rue flowers grow best in full sun, but part shade is also tolerated. Plants will produce fewer flowers in the shade.
Good, fast drainage is important for healthy rue plants. Add sand, perlite, or vermiculite to the soil to help drainage. Use raised beds with prepared soil in gardens where heavy clay dominates.
Common rue is very drought tolerant and is a good candidate for a xeriscape or rock garden. Do not irrigate rue, except for periods of extensive dry weather.
Temperature and Humidity
Rue flowers thrive in hot weather and low humidity, similar to its native habitat of Greece, Turkey, and Italy.
Do not fertilize rue plants. Excess nutrients will cause the plants to produce more foliage at the expense of the flowers.
Rue is a woody perennial that flowers in late spring on fresh, new wood, so the standard practice is to trim the stems down to old wood in early spring, before new growth begins. Old, woody plants benefit from especially hard pruning.
It's easy to make new rue flower plants through stem cuttings. The stems root quickly in moist sand in warm weather. Take cuttings from fresh new growth in late summer, but take care not to touch the sap when handling the cuttings.
How to Grow Rue From Seed
Rue is easy to start from seeds in the garden or in trays. Sow the seeds on the surface of the soil or coarse potting mix under conditions that are at least 68 degrees Fahrenheit. The seeds need light to germinate, so don't cover the seeds. When the seedlings develop at least two sets of true leaves, they can be transplanted into the garden or into larger pots.
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.
Potting and Repotting Rue
The bluish foliage of rue plants marries well with plants that have golden foliage, like 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, and blend well in mixed containers.
You can grow rue in just about any pot filled with sandy or chunky well-draining soil. Make sure to use a well-draining container and wear gloves and long sleeves when handling these plants. Repotting is necessary when you see roots coming out of the drainage holes of the pot.
When it comes to harvesting rue, it is best to limit its use to pest repelling, for safety reasons. Although rue is still used in minute quantities to flavor food, the FDA prohibits its use in food products.
Wear gloves to avoid skin irritation when handling rue. Harvest rue by cutting down the entire plant at ground level. Hang the plant in a dark, dry place until the leaves become brittle. You can make rue sachets to discourage fleas and ants, but don't place the sachets in pet beds, as the smell is unpleasant to cats and dogs as well.
Common Pests & Diseases
If you see caterpillars feeding on your rue flower plants, don't spray them. It's likely that they are swallowtail butterfly caterpillars, which use rue as a host plant. Rue plants can get root rot in wet soils, but seldom suffer from other pests or diseases.
Rue vs. Fenugreek
As another bitter herb that bears small yellow flowers, it's easy to confuse fenugreek (Trigonella foenum-graecum) with rue. Fenugreek, however, is an annual legume and does not have some of the properties that rue flowers do. You can grow fenugreek in the sunny garden after all danger of frost has passed, and use the ground seeds in curries, or use the leaves in salads.