Hundreds of years ago, before all things herbal was a trend, people were growing rue as a medicinal plant. Rue is a mysterious plant with broad-ranging and seemingly oppositional 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. Even if you don't explore the herbal uses of this strong-smelling plant, you will appreciate the way its summer blooms draw butterflies and beneficial parasitic wasps to the garden. When not in bloom, the bluish-green petite foliage is a handsome asset in the flower and herb garden.
|Botanical Name||Ruta graveolens|
|Common Name||Common rue, herb-of-grace, herby grass|
|Plant Type||Perennial herb|
|Mature Size||18 to 24 hours|
|Sun Exposure||Full sun|
|Soil Type||Average to poor|
|Soil pH||Slightly acidic to alkaline; ph 6.5 to 8.5|
|Hardiness Zones||USDA growing zones 6 to 11|
|Native Area||Southern Europe|
How to Grow Rue Flowers
Choose a sunny site with good drainage for your rue flowers. If your garden has heavy or wet soil, consider container culture. Rue flowers are good candidates for tough sites, and will even grow in gravel.
Rue flowers grow well in full sun, but partial shade is also tolerated. Plants will produce fewer flowers in the shade.
Sharp drainage is important for healthy rue flowers. Add sand, perlite, or vermiculite to the soil to help drainage. Use raised beds in gardens with heavy clay. Mulch plants in the winter in growing zones 4-6 to help plants survive the winter.
Common rue is very drought tolerant, and is a good candidate for the 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, which resembles its native habitat of Greece, Turkey, and Italy.
Do not apply fertilizer to rue flowers. Excess nutrients will cause the plants to produce more foliage at the expense of the flowers.
Potting and Repotting
Wearing gloves and long sleeves, pot up your rue in a sandy loam or other chunky, well-draining soil. Repotting is necessary when you see roots coming out of the drainage holes of the pot.
Propagating Rue Flowers
It's easy to make new rue flower plants through stem cuttings. The stems root quickly in moist sand in warm weather. Take care not to come into contact with the sap when taking cuttings.
Toxicity of Rue Flowers
Rue has toxic properties both from external contact and from ingestion. The plant's oils can cause skin blistering similar to a poison ivy rash. When ingested, the herb can cause severe gastrointestinal upset, and is especially unsafe for pregnant women.
Time you pruning to your desire to have flowers. To prevent flowering, prune plants hard in the spring. If you desire flowers, prune plants to shape after flowering. Old, woody plants benefit from a hard pruning
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, its toxicity is significant enough that the FDA prohibits its use in food products.
Wear gloves to handle rue to avoid skin irritation. 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.
Being Grown in Containers
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.
Growing From Seeds
Rue plants will self-seed, sometimes aggressively in warm areas. You can collect the brown seed capsules in late summer after flowering. Rue seeds need light to germinate, so don't cover the seeds. Place them on moist sand, and keep at about 70 degrees F for germination to occur in one to three weeks.
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 flowers 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 flowers. Fenugreek is an annual legume, and does not have the toxic properties that rue flowers do. You can grow fenugreek in the sunny garden after all danger of frost has past, and use the ground seeds in curries, or use the leaves in salads.