Rue (Ruta graveolens), also called herb-of-grace, is a pretty subshrub with attractive blue-green cut foliage and yellow flowers that seems to be increasing in popularity these days.
While rue was once used as a medicinal plant, notably as an abortive, the unpleasant reactions that follow its use (severe abdominal contractions, vomiting, bleeding, and sometimes death), as well as its highly unpleasant smell, mean that it is now rarely if ever used in medical treatments. In small quantities, the foliage was also once used as a culinary herb, in small quantities, for its bitter taste, a practice still in use in some European and northern African countries, but even there, it is less and less popular.
Rue would probably have been mostly forgotten had it not be “resurrected” by companion planting. It is said to repel cats and certain insects, although my own cat, the dearly departed Geisha, used to sleep right under a rue plant and wasn’t bothered in the least.
Rue can also be quite ornamental, with very attractive foliage and reasonable flowers (personally I find they distract from the foliage, though); a plant you might want to use in a dry, sunny spot, as it tolerates those conditions.
It’s really a subshrub, with branches that are woody at the base, but is grown as a perennial. Under most garden conditions, it reaches about 18 to 24 inches (45 to 60 cm) tall with a spread of 8 to 12 inches (20 to 30 cm), but it can grow taller in milder climates where its woody stems are not cut back by frost. It is hardy to about USDA zone 5 (AgCan zone 6), although with good snow cover, you can get it to grow well beyond its normal zone.
Noli me tangere
Pretty or useful as you may find rue, you won’t want to handle it much, especially if you have sensitive skin. That’s because it is phototoxic, that is to say, if you touch it or rub against it on sunny day, it could lead to a very unpleasant skin reaction: redness, irritation, burns, blisters, etc.
Note the term “photo” in the word phototoxic: it means that the skin must be exposed to sunlight (especially ultraviolet light) following contact for a reaction to occur. It you touch the plant on a cloudy day, or early in the morning or late in the afternoon when the sun is low, for example, there will be no reaction. But when the sun is out, be careful!
Note too that sensitivity to rue sap increases with the number of exposures. You may not react at all at first, but irritation can appear after repeated exposures and from then on, becomes increasingly severe.
What to Do?
If you touch rue by accident, just wash your skin just with soap and water. If you have to actually handle rue (planting or pruning, for example), do it on a cloudy day or wear long-sleeved gloves. Especially avoid getting any sap in your eyes.
It’s important to be aware of the less positive aspects of the plants we grow: after all, forewarned is forearmed!