Don't Kill That Caterpillar!

Black Swallowtail on Butterfly Weed (Asclepias tuberosa)

Butterflies look so slow and docile, gently flitting about the garden. Just get our your camera and try to catch them in their daily duties of sipping nectar out of flowers; you'll quickly see they are shy, move fast and don't like being photographed.

I doubt their eyesight is so great they can see me, but maybe they can. I guess if you're an inch tall and a looming giant, 500 times bigger than you are and carrying a menacing black box with a big moving eye-lens, you might run, too.
Weak, tired and with much of her color worn down, she drank nectar for a day before laying eggs.

Maybe they simply sense a person following them in the garden. After all, their senses must be impeccable, or else they couldn't travel great distances. This Monarch butterfly, above, on the white flowered chives, showed up just as the chives were blooming. As you know, Monarchs spend their winter in South America and manage to navigate northward as the weather warms in spring. This one was worn to a frazzle, weak, but sipping nectar in order to regain her strength for laying eggs for another generation of Monarchs.

A Tiger Swallowtail, dishing up breakfast from dianthus in my edible flower garden.
Most people seem to like butterflies, but many of those same folks have no hesitation for stomping caterpillars. This time of year you'll notice what we always called "dill worms" when I was growing up.
The caterpillar of the Black Swallowtail Butterfly on a fennel leaf.
Black Swallowtail butterflies lay eggs on: fennel, dill, parsley and related plants. Those hatch into the caterpillar you see above. The caterpillar hangs around on one leaf and eats most of it, then pupates, building a little cocoon around itself and hanging there in a little hammock until it has grown. The cocoon splits and out comes the adult Black Swallowtail.
The majestic Black Swallowtail, newly hatched.
An older Black Swallowtail, on oregano.
The list of herbs that attract butterflies is long and extensive. A few you might want to plant if you wish to attract butterflies: Mint, oregano, butterfly weed, Mexican butterfly weed, rue, dill, fennel, parsley, sage, rosemary, thyme, lemon balm, roses, sweet marjoram, hyssop, chives, monarda, yarrow - the list really is quite long.
Monarch caterpillar, see how different they look from the Swallowtail caterpillar?
Monarch caterpillars, however, hang out, sip nectar and lay eggs on butterfly weed (Asclepias tuberosa) which is in bloom right at the time Monarchs are looking for food and home. In case you don't recognize butterfly weed, here's a picture, below. Note that lots of butterflies like the nectar from this plant but it's the Monarch that likes to hang its hat there.

Fritillary butterflies on butterfly weed.
Here in the Ozarks, the butterfly weed is a common roadside plant, starting its bloom around the end of May. This is an old-time medicinal plant, sometimes called, "pleurisy root" because of its use in treating that ailment.

So, if you see, "worms" in your herb plants, let them be, they turn into butterflies or moths and they're not going to ruin your plants. You'll be glad you left them alone when they turn into butterflies! And if you're going to photograph them, well, give yourself more time than you think you will need, they can run faster than you can.


Sharon Lovejoy said...

Dear Jim,

Thank you for this posting, which is marvelous and timely. Isn't it amazing that folks will kill caterpillars without a second thought? But then, many just don't realize what they're doing.

I love this posting.

All joys,


Myra Stiles said...

Great pictures!

CDfolia said...

Wonderful photo's. I'm envious of the range of butterflies you have. Our Scottish selection is much smaller and the colourful ones have declined drastically in the last 30 yeas (due in part to stomping by overzealous gardeners no doubt).

In my area every seems to be paving their gardens so they can park their cars so there is very little habitat for wildlife, though my own garden is full of insect delights (and, to be fair, horrors, which I'm sure you'd be able to fry up for lunch if you were my neighbour).

I'd love to invite you to join the Folia garden tracking website, you'd be an absolute boon on their and I imagine you'd be a hit on the their wildlife forum groups too.

I'd love to see you on there so here's an invite so you can look at my page to get an idea how it works and if you want to join (it's free) you can do so via the menu at the top. http://www.myfolia.com/gardener/CDfolia/invite

It lets you add links to all other places you can be found on the web so more people would find your blog as well.

Lemon Verbena Lady said...

I had to get up in front of my herb club and announce that members were killing caterpillars when they were working in the herb garden! We were trying to attract them with a pollinator and butterfly herb garden and it worked, but we should have been doing ID of caterpillars as well! Great information as always Jim!

Dylan said...

I have grown herbs for about 6 years now and have never noticed any caterpillars on them until this evening I saw a Black Swallowtail Butterfly caterpillar on my fennel. I grow Mint, oregano, dill, fennel, sage, rosemary, thyme, lemon balm, sweet marjoram, chives, and yarrow. From reading the information on your blog, it seems that they will not harm the herbs, and I'm hoping that's the case. Can you please verify if that's so? Thank you!

Jim Longs Garden said...

Congratulations! Having black swallowtails is one of the joys of summer. And you're correct, the caterpillars are not harmful. On fennel, the caterpillar will eat one leaf. On parsley it may eat 2 or 3 leaves, but the leaves quickly grow back.

To have more black swallowtail butterflies, plant some more parsley, dill or fennel. That one caterpillar, when it turns into a butterfly, will come back and lay eggs to make more caterpillars, and you will soon have lots of these beautiful butterflies in your garden. No matter how many butterflies you have, the enjoyment of having them in your garden far outweighs the few leaves they eat.

Happy gardening!