Regional Gardening Reports :: National Gardening Association

In the Garden:
Northern California Coastal & Inland Valleys
August, 2007
Regional Report

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This handsome fellow is munching his way to beauty in the Cal Train parking lot!

Be a Friend to Fennel

I see people busy clearing the wild fennel from their yards and empty lots. It breaks my heart because if you look closely at the elegant, ferny plants, you will see a multitude of Anise swallowtail caterpillars (Papilio zelicaon) munching away at the foliage. Wild fennel (Foeniculum vulgare) is often mistaken for anise or dill. It is prevalent along roadways and in open fields. You can recognize it by its towering height (up to 10 feet!), the cap of lacy yellow flowers, and the foliage that's tasty to humans and swallowtails alike.

Wild fennel seems to thrive on neglect, needing neither water nor care of any kind. To survive the long, dry California summer, it has a tap root that forges through even the hardest adobe clay soil. Try to dig one of these hardy plants from the ground and you will see what I mean.

If you brush the foliage with your hand, the plant exudes a pleasing licorice scent. You can eat the fern-like foliage in spring, dig tender roots in early summer, and harvest the seeds in fall. No wonder the swallowtail butterfly finds refuge here -- it's delicious!

Wild fennel has been used for medicinal purposes since ancient times. The Egyptians used it as a diuretic and to solve digestive problems. The Greeks also used it medicinally as a natural antacid.

How it Begins
In the early part of summer, a female swallowtail butterfly lays her eggs on the fennel plant. The eggs hatch into tiny caterpillars that look more like ladybug larvae in their early stages. As the tiny caterpillars much on the sweet fennel, they grow larger and larger, casting off their old skins as they grow. The caterpillars are camouflaged to protect themselves from predators. I imagine that a nice fat caterpillar would be a yummy treat for a hungry bird. It may be difficult to spot them right away, but look carefully among the foliage and you will find them.

A swallowtail caterpillar sheds its skin four or five times during this stage of life. Eventually, when fully grown, the caterpillar creates a silk pad on a sturdy twig and attaches itself to the plant. The skin splits for the last time as the caterpillar enters the pupa stage of life. It doesn't spin a cocoon like a moth; in the final stage of the shedding process the skin hardens to form a case around the caterpillar. It remains in this pupae state until it unfurls its wings and emerges as an anise swallowtail butterfly.

Live and Let Live
Now here's the rub: Those caterpillars have gone to all that trouble to turn themselves into beautiful butterflies. They aren't bothering anybody; they have made their homes in the weeds and are not eating your good garden plants. But all of a sudden, somebody gets a bee in their bonnet that they are going to "clean up" the yard and the next thing you know, the fennel plants have been chopped down and tossed into the compost pile, along with the butterfly chrysalis. Or worse still, sent off in a garbage truck!

Please, if you have wild fennel on your property, wait until the foliage dies back before you do your clean-up job. The anise swallowtails will thank you, and so will I!

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