Swallowtail caterpillars and rue

Swallowtail caterpillars are decorating, and eating, the rue planted here and there in my garden beds.


The caterpillars are beautiful, and contrast so well against the blue green foliage of the rue. The yellow on the caterpillars’ body even matches the shade of the rue blossoms.


I don’t mind that they are making a meal of the rue’s tender leaf tips or have munched off some of the flowers. Rue (Ruta graveolens) easily self-sows in my Connecticut gardens. A few volunteer rue have sprung up here and there from seeds dropped by the mother plants last year. These caterpillars are actually doing me a favor. Their meal of rue flowers and leaf tips means less deadheading for me later this season. Plus, I anticipate the joy of watching black swallowtail butterflies (Papilio polyxenes) flit about the gardens after the caterpillars have their fill of food and undergo their amazing transformation.

Rue is an aromatic, shrubby perennial preferring dry, rocky soils. It’s a perennial with both positive and negative attributes. Rue has dainty, rounded, blue-green leaves and, with a small bit of shaping, grows into a 1-2 foot rounded form. It’s yellow flowers attract pollinators and, in my area, one big plus is that deer do not browse rue shrubs.

Rue is often mentioned as a traditional herb garden plant. While historically listed as a medicinal herb, rue leaves can be toxic if ingested (seems that deer know this!), and the sap can cause a blistery skin rash.  If you have sensitive skin, do not work around rue unless your hands and arms are well protected. I’ve grown rue for years and, though very sensitive to poison ivy, I have not developed a rash from rue. Still, when pruning rue I’m careful to keep sap from contacting my skin.

According to the Missouri Botanical Garden website, rue is native to Southern Europe. It’s self-sowing habits have allowed it to spread in some areas. It’s best to deadhead rue flowers to prevent seed production. Plants will self-sow if seeds are left to form and fall. Visit  the Go Botany page about rue to learn more.

Fortunately, black swallowtails use plants besides rue as hosts. If you rue the thought of growing rue, you can attract black swallowtails with plants in the parsley (Apiaceae) family such as Queen Anne’s Lace, carrots, dill, and celery.

Have you seen any of these caterpillars in your garden this year?

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2 comments for “Swallowtail caterpillars and rue

  1. June 13, 2013 at 9:08 pm

    I don’t grow rue, but I do see these funny striped guys on my dill and they are out in the meadow where the Queen Anne’s Lace grows. I’m looking forward to seeing the butterflies when the time comes!

    • June 14, 2013 at 9:09 am

      Laurrie, I see the same caterpillars on Queen Anne’s Lace during the summer. This is the first I’ve noticed them this early on rue.

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