Like some people, some plants don’t get the respect they deserve. One of these is Dog Fennel. The name suggests an inferior type of fennel, but it’s not at all related to fennel, which is a culinary herb imported from the Mediterranean. Dog Fennel is a native plant that grows mostly in the southeastern United States. You should not eat Dog Fennel because it contains a toxic chemical called pyrrolizidine. This won’t kill you right away but it can cause liver damage, and you don’t want that.
The plant I’m talking is Eupatorium capillifolium. The Latin name is important because there are three other plants called dog fennel that also are not related. If you google either name you will find scads of information on how to eradicate this plant. It’s considered a nuisance weed which will overtake pastures, hay fields, and cropland if not kept in check. If you don’t watch out, it will also invade your yard and garden.
However, I let a few plants grow in my yard and along my driveway. I’ve always liked Dog Fennel, in moderation. In spring, feathery green shoots emerge from last years’ roots or seeds. Over the summer they grow into graceful fountains, three or four feet high, or taller. Sometime in October, tiny white blossoms burst out, abuzz with bees, butterflies, and other insects. If you get close enough, you can detect the flowers’ delicate scent. When winter comes, Dog Fennel is reduced to brown skeletons that persist until you, or time, knock them down. I break off any stems that are in my way, but I leave a few to shelter beneficial insects and their larvae during the winter.
There is an old saying that when the Dog Fennel blooms we have six weeks until frost. Over the years I have observed this and found it to be generally true. The past two or three years I’ve recorded the time of blooming on my calendar and found it to be uncannily accurate. In fact, Dog Fennel blooms earlier in open areas than in more sheltered ones and the frost follows accordingly, within a few days of the six weeks’ date.
A few years ago, a dog fennel seed landed inconspicuously on one of the garden beds at the elementary school. That compost-rich soil nurtured it through the summer. By the time school started, it towered over all else in the garden beds. When we weeded the gardens in preparation for fall planting, I left it alone, for a time, because it looked nice and wasn’t in the way, yet. When I tried to pull it out, I found that the root system was as massive as the upper part. The time came to use extreme measures to get this weed out of the garden, but first I wanted to know if it had any redeeming qualities other than those I already mentioned.
Googling and following links, I came across a reference to the Scarlet-bodied Wasp Moth. This colorful insect may look like a wasp but it’s really a moth and doesn’t sting. In fact, it is not known to cause any damage to nature or mankind. The larvae feed on wild hempvine, a plant with heart-shaped leaves and white blossoms.
Be on the lookout for this beauty if you live in Florida, along the Gulf Coast or in coastal Georgia or South Carolina.
Here’s where things get interesting. Adult butterflies and moths usually feed on nectar. That’s why they are considered pollinators. The adult male of this species feeds on Dog Fennel. He pierces the stems with his proboscis to obtain the toxic pyrrolizidine alkaloids. These chemicals do not poison our moth but make him distasteful to whatever would otherwise eat him. He also stores the chemical in little pouches under his abdomen.
The story gets more interesting. When he finds a lady friend, our gallant moth showers her with these compounds, which in turn protects her from predators. And even better, when she lays her eggs, they will contain these protective chemicals. The Scarlet-bodied Wasp Moth is the only insect known to transfer a chemical defense in this manner.
The caterpillar is quite harmless.
So, if the male doesn’t have Dog Fennel to feed on, his mate and their eggs are more susceptible to being eaten. In other words, no Dog Fennel plants mean fewer Scarlet-bodied Wasp Moths. Doesn’t this earn Dog Fennel our respect? It earned mine, and that of the children at the school. With no other Dog Fennel in the vicinity, we decided to leave the plant alone for the time being.
I don’t mean you should let your garden or pasture become overrun with Dog Fennel. A few plants here and there, along the fence or driveway or roadside, should be enough. These are small moths. They don’t eat much. If you find hempvine on your property, let it grow. If you have none, plant some for their babies. Then be on the look out for this pretty moth. And when the Dog Fennel blooms this fall, make a note of the date and wait to see if it predicts the first frost.
This homeowner understands the beauty of Dog Fennel. Unfortunately, this is not my yard.
marieqrogers 