Rue: The Benefits (and Dangers) of this Lesser-Known Herb

Several years ago, I picked up a small herb plant at a local nursery. The bluish-green foliage with its signature three-pinnate, spatulate leaves caught my attention initially. The plant tag identified it as rue (Ruta graveolens). I wasn’t familiar with it at the time but I brought it home and planted it in one of my herb beds to observe and study.

I had no idea how much I would come to enjoy rue in the garden and what an important role it would play in my garden. It adapted to the hot climate well, and quickly transformed from a modest herb into an expansive shrub that later bloomed with yellow starburst-like flowers. 

Those bright flowers acted as a magnet for so many pollinators including bees, butterflies, flies, and wasps. But it wasn’t just the flowers that brought in pollinators. I soon discovered its role as a host plant for certain swallowtail butterflies.

Yellow rue flowers
In the summer rue blooms with small, delicate yellow flowers that have a green center.

A Surprising Discovery

One morning on a stroll through the garden I noticed something on the rue plant that had become a familiar sight on other herbs in my garden over the years – black swallowtail caterpillars. Dill was growing nearby, which they typically would have been devouring. 

Black swallowtails still lay eggs on those other herbs but they seem to favor the rue. The next spring, I saw a very large butterfly floating around the rue plant and then landing on it and laying eggs. 

When I looked closer, I saw that it was a Giant Swallowtail laying her eggs on the rue. That was the first time that particular butterfly species had laid eggs in my garden. She definitely came for the rue as it’s one of their favored host plants.

Swallowtail butterflies are a favorite sight in the garden so I was overjoyed to find that this plant added additional support for them.

Rue is a host plant of the Giant Swallowtail caterpillar. This one must have felt threatened by my presence - it has its osmeterium in full display.

More Than Just Pretty Flowers

We often value a plant for its showy blooms. I have learned over many years of gardening that when the flowers go to seed, the seed heads can offer just as much visual interest.

That first year that I added rue to the garden, I also noticed that as summer ended and autumn drew closer, those yellow flowers became attractive seed heads, adding color and texture to the fall landscape. 

After observing it in its full lifecycle and watching it support a variety of garden life, I knew I needed to learn more about this herb.  I was surprised by what I discovered about the benefits of rue, its storied past, and a few hidden dangers. 

The beautiful seed heads in the late summer and fall are one of my favorite things about rue.

A Journey Through Time: The History of Rue

Rue (Ruta graveolens) is native to the Mediterranean, as many of our beloved herbs are, and so it’s very tolerant of hot and dry soil conditions. With a rich history that spans back to ancient times, it was an important culinary and medicinal herb, known for its unique flavor and medicinal properties. It boasts a bitter and somewhat unpleasant pungent scent and flavor, which led to it being associated with the verb rue – “to regret”. 

As a culinary herb, rue has fallen out of favor in modern cooking. Our taste preferences and choices have evolved, and the use of an herb that imparts a bitter undertone to a dish is less common in the American palette today. However, it can still be found in some traditional Italian recipes, passed down through generations of cooks. 

Fascinating Folklore

In addition to its culinary uses, rue held a significant place in folklore and religious practices. It was believed to be a talisman against witchcraft. This belief evolved into the Catholic Church’s practice of dipping branches of rue into Holy water and sprinkling it over the heads of parishioners as a blessing. This practice earned it the common name of “herb of grace.”

The botanical, Latin name of “Ruta” comes from Greek, translated as “to set free,” referring to its use as a chief ingredient in mixtures used as antidotes to poisoning.

In medicinal traditions, rue was often used for a variety of maladies such as a treatment for varicose veins, uterine disorders, and nervous complaints.

Rue foliage
Rue's pale green spatulate leaves add ornamental interest to the garden, but handle with care! Rue's sap can cause rash and blisters in some individuals when exposed to the sun.

The Dangerous Toxicity of Ruta Graveolens

While rue has a long history of folk medicine, it is essential to exercise caution if using this herb. There have been some interesting studies on its possible medicinal use in restoring neural function, but the safe dosage for human consumption has not been determined. Many medical sources advise against using rue due to the potential dangers of toxicity in large amounts. 

Rue is still used as a cooking spice and beverage flavoring in some cuisines, but ingesting it in higher doses has been reported to cause gastric distress. It can also be toxicity to those with liver and kidney problems, and can even lead to the termination of pregnancy. For these reasons, I use it as an ornamental herb only. 

It is also crucial to handle this plant with care. Because rue has a phototoxic sap, many individuals experience skin allergies in the form of burning sensations and blisters when exposed to rue in the sun. It is advisable to wear gloves and long sleeves and only work with or near the plant during cooler hours to minimize the risk of skin irritation.

The Ecological Benefits of Growing Rue

Besides culinary and ancient medicinal and magical uses, rue offers a range of ecological benefits, making it a valuable addition to any garden. As an evergreen herb or small shrub with bluish-green leaves, rue adds beauty and texture to the landscape. Its clumping habit and compact size make it suitable for various garden designs, from rock gardens to borders.

Rue is adaptable to different soil conditions, including poor, sandy, and rocky soil. Once established, it’s a drought-tolerant plant, making it an excellent choice for gardens in hot and dry climates. It is hardy from Zone 6 and warmer, making it suitable for a wide range of regions.

Growing rue revealed to me that it serves as a host plant for specific butterflies. As I discovered, both the Black Swallowtail and Giant Swallowtail butterflies rely on rue as a host plant for their caterpillars. It’s also a favorite host plant of the Anise Swallowtail. 

In addition, the flowers provide pollen to a variety of insects including wasps, flies, and bees. Rue’s ability to attract and support pollinators adds vibrancy and life to the garden. 

Fraternal potter wasp on rue flower
Wasps are pollinators too! This fraternal potter wasp is one of many insects that visit the rue flowers in spring and summer.

Cultivating Rue: Tips for Successful Growth

Growing rue is a rewarding experience, and with the right conditions and care, it can thrive in the garden. Whether starting from seeds or cuttings, rue is relatively easy to propagate. Surface-sow the seeds in a warm, sunny area, as they require light for germination. The germination process typically takes one to four weeks.

Once the rue plants are big enough, they can be transplanted into well-drained soil in full sun. Rue’s adaptability to poor soils, makes it an ideal choice for challenging gardening conditions.

It is important to avoid over-watering, as rue is susceptible to root rot. Established rue plants are drought-tolerant and can survive in extremely dry conditions. 

The Potential to Become an Invasive

Rue grows so effortlessly in my garden and tends to want to fill up the raised bed it’s in. It has the potential to become invasive if not properly managed.

While it typically does not spread aggressively in my garden compared to other herbs, allowing the plant to reseed itself without control can lead to unwanted proliferation. Removing seed heads after blooming can prevent the plant from uncontrolled growth.

I prune it back in late winter or early spring and pull any new seedlings that have come up around it. Cutting the plants down to 3-4 inches also allows for rejuvenation. Within a couple of weeks, the plants will rebound, appearing strong and healthy.

Rue seed heads
If rue begins to spread too agressively, you can remove seed heads to prevent uncontrolled growth.

Rue: An Undervalued Addition to an Ecological Garden

Rue is an often overlooked plant for the herb garden with a fascinating history and a range of ecological benefits. 

Fortunately, I don’t experience skin allergies from this plant but many people do.  So be careful if you try to grow rue, as the skin reactions can be quite severe and scarring in some folks.

Even though I don’t use it for any culinary purposes, for me, its role as a host plant, a pollinator magnet, its ornamental properties, and its adaptability to various growing conditions make it a perfect addition to the garden.

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Cultivating Nature's Wisdom

I’m a nature photographer and gardener sharing how I created an ecological garden in a small suburban backyard. I also share a few tips for growing and using herbs to craft your own homegrown spice blends.

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