Rue for Giant Swallowtails

Common Rue, Ruta graveolens, is not grown in our area very often because its native environment is warmer and it can be fussy about surviving an unusually cold winter.


Rue gets special treatment in our garden is because it is the only plant we grow that is used by Giant Swallowtail butterflies to raise their caterpillars. Rue’s poisonous leaves make the caterpillars taste bitter to predators so they are left alone.

Giant Swallowtail in our garden last summer

The expression, you will rue the day came from the plant’s less desirable characteristic of causing rashes and blisters on some people. Families with young children and gardeners with sensitive skin should avoid all parts of Rue plants.


Greek, Mediterranean and Chinese cooking use Rue as a culinary herb. It provides the bitter flavor in grappa con ruta and in Ethiopia it is added to coffee. The Chinese add it to mung bean soup.

Historically, Rue was used as a medicinal herb. It was taken daily in small doses to prevent sorrowful events such as assassinations. It was called the Herb of Grace when its leaves were added to holy water to bless sinners and keep them safe.

In Shakespeare’s garden, Rue was a sign of joy. In England it was called the judge’s plant because it was suspended over judges’ heads or on their desks to protect them from jail fever.

Rue has been used by and against witches, according to Michael Drayton. Aristotle said that the Greeks used Rue as an antidote to indigestion that bewitched them. A bundle of Rue was used as a witch finder.

Michelangelo, da Vinci and other Italian artists ate rue to sharpen their creativity and eyesight during prolonged working periods. The bitter taste was said to awaken their senses.

In World War Two, rutin, an extract of Rue, was used to treat high blood pressure and Rutin tea is still available. Rutin is also found in watercress, capers and orange peel. Crushed Rue leaves are used to cure skin problems such as cysts.

Rue is a member of the citrus plant family so it is its citrus oil that causes skin rashes. The same is true of orange, lemon, kumquat and lime oils. Rue’s cintronella scent repels dogs and cats.

As a garden plant Rue is a beautiful asset. The leaves are blue-grey and the flower clusters are bright yellow. It is suitable for a sunny, dry, xeriscape bed where it would receive regular but minimal water.

Giant Swallowtail caterpillar on Rue

Ruta graveolens has become naturalized and grows in the wild in many states, including TX, NC, AL, and CA.


Rue grows reliably from fresh seed so buy seeds marked for this year. The seeds can be planted directly into the flower bed in the fall or after the last frost. Usually the seeds are sown indoors over the winter and small plants are put out after the last spring frost.

I’ve also had some success taking cuttings in the fall and rooting them over the winter.

The plant is a great blue border plant that will grow to about 3-feet tall with woody stems. Prune the growing tips back after the summer flowers fade, to keep it bushy and full.

The Giant Swallowtail butterfly lays eggs on trees and herbs in the citrus or Rutaceae family including Navel orange, Rue, and Meyer's lemon.

Giant Swallowtail lays a single egg at a time.

The female Giant Swallowtail lays single eggs on the top of young leaves.

Here you can see the single egg laid on top of the leaf.

These butterflies have a wingspan of 4 to 6-inches. Their upper-side is dark with a yellow chevron and the wing’s under-side is yellow.

The caterpillar is called an Orange Dog by the citrus industry.

Plant source: www.mountainvalleygrowers.com; seed source: http://www.seedaholic.com/.