Dogfennel Indicates The Arrival of Cold Weather
The official beginning of winter is a little under six weeks away and Wakulla County has had a few cooler, but not cold, mornings so far this November. Still the landscape reflects the diminishing hours of daylight and the impending winter’s nap for many plant species.
Sweetgum, dogwood and hickory leaves have changed from their summer green to traditional autumn hues. All are dropping seed which are being plundered by the birds and squirrels who are preparing for the looming season of privation.
The wildflowers are fading, too. Partridge pea’s blooms are now seedpods and golden rods are quickly converting to fluffy down covered seed for scattering by the wind.
However, one native plant is still producing big clusters of tiny white flowers. The perennial dogfennel is adding a cloudlike texture to open areas in in the county, and the southeast.
Dogfennel (Eupatorium capillifolium) is not in the plant family with the herb fennel, nor is it of particular interest to dogs. This herbaceous plant, having green stems and no bark, is in the family with sunflowers.
This time of year dogfennel is commonly between two to seven feet in height with several stems which fork from a sturdy and securely rooted base. The stems and base are covered in fine leaves which resemble branching green threads projecting outward in a delicate drooping mass.
Fallow fields, road shoulders, and other disturbed sites are ideal spots for dogfennel to flourish. This plant’s population is denser in full sun, but it will grow in partial shade.
When the thick foliage and flowers are crushed, they produce an unpleasant acrid odor. This negative trait and quickly wilting blooms have eliminated this plant’s potential use as a cut flower source.
This plant is exclusive to North America and several Caribbean islands, but has been introduced out of its native range as an ornamental. While it is normally considered a nuisance weed to agricultural producers, it does have its place in folklore and the native environment.
There is the belief that the first frost of the season is just a few weeks away when dogfennel blooms. The excellent odds of this being factual is based on dogfennel’s late season flowering genetics, not some unknown stimulus which causes a weather forecast from this weed.
The environmental importance of dogfennel is its use by the Scarlet-bodied Wasp Moth, (Cosmosoma myrodora). Only the males of this insect species consumes this plant as a means of repelling hungry prey.
The plant tissue of dogfennel contains an alkaloid toxin, pyrrolizidine. In mammals this compound causes liver damage and potentially fatal fluid retentions.
A bitter taste is present in the adult male Scarlet-bodied Wasp Moths which consume the toxin laden leave tissues. The female moths do not eat dogfennel, but they are showered with the chemical from the males as part of the reproductive process.
If dogfennel was not consumed by this brightly colored and gregarious moth, many more would fall prey to predators. They are potentially on the menu for large spiders, birds and small mammals.
Soon the wispy white blooms will be replace by sparkling frost in the early light of day.