Nature Notes
Intriguing Use for Smartweed Found in 1891 News Account
By Patricia Martin

A couple of days ago a neighbor of mine called to me from the street and asked me if we had "smartweed" on the Island. I replied yes, and he went on to say that in the paper it was written that smartweed used to be used to keep flies away from horses. As both of us are horse people and flies have been a problem this year, I figured this should be looked into. In last week's paper the reference to smart weed occurred in the "Looking Back" column under the section for July 25, 1891. In case you missed the column, it said "to keep flies from horses, bruise a

bunch of smart weed until the juice exudes, and then rub the animal with the bruised weed, paying special attention to the legs, neck, and ears. When it's cold, apply with a sponge." Now I had never heard of this use for smart weed and so I was intrigued.

Smartweed is a common name that refers to several species of plants in the Polygonaceae, otherwise known as the smartweed or buckwheat, family. On Mackinac we have four species of plants in the genus Polygonum, which some might have referred to as smartweed. The knotweeds or smartweeds are a large group of often weedy plants with very small flowers of five petal-like sepals which grow in spikes or spike-like racemes or in the leaf axils. The stems are jointed and the stems immediately above each joint are surrounded by a membrane called a sheath.

One species, which I'm pretty sure was not the one referred to in the paper, is well known to gardeners around here and is commonly known as blackbindweed or false buckwheat (Polygonum convolulus). This plant is a small vine with heartshaped leaves and small greenish flowers. It likes gardens and often is a weed entwining flowers or vegetables.

A second possible candidate for the "smartweed" referred to in the column is usually called bushy knotweed (P. ramosissium). It is an erect plant with many simple or bushy forking firm upright corrugated branches. It can stand up to six feet tall and looks yellowish green. The leaves are lanceolate to linear with a point on the end. The small green flowers are found one to several in the axils of the upper leaves. This plant is found on sandy or gravelly shores along the Great Lakes or disturbed sandy sites slightly inland.

One species that could very well be the one used on horses is known as water smartweed (P. amphibium). These plants generally, as their name suggests, live in water or in wet soil. This perennial plant has a slender and tough forking rhizome, stolons, and rooting system. Its branches are elongated, simply leafy to the top, and the leaves are elliptical oval to lanceolate with petioles, but the shape is somewhat variable depending if they live on land or in the water. Those that live on land have leaves that are more slender and pointed. Those that live in the water have more blunted leaves or one with short points. Like all the knot or smartweeds, the stems are jointed. The flowers are rose-colored and grow in blunt spikes about one inch long by one-half inch wide.

Another very similar species to water smartweed that grows on Mackinac is known as willow-weed or nodding smartweed (P. lapthifolium). It is again a species of moist shores, marshes, river margins, and damp waste ground. These plants may grow one to six feet high. Their flowers are in long dense spikes that are only one quarter to one third of an inch wide and the ends of the spikes droop or nod. In most cases, the flowers are again pink, but they sometimes may be white or even purplish. The stems are smooth and the sheaths are mostly without fringe.

I've found a variety of uses for different smartweeds. For instance, water smartweed was used as an antidote for poison. The root has been used for an astringent, a blood purifier, and for treating sores of the mouth. One record states that the flowers were dried and smoked to attract deer to a hunter. In some areas, it was used as an aromatic hay but only that which was taken from the water, not from the land, and it was thought to have higher protein value than other fibers.

In addition, other knotweeds or smartweeds have been used for treating arthritis, lung problems, diarrhea, jaundice, and chronic eczema. The juice is sometimes applied to wounds, bruises, and cuts, and for drawing pus out of sores, but it's irritating to sensitive tissue and must be used with care. There are a number of other uses as well.

Despite looking in all of my many herbals and other plant books, I've not found any reference to the use of smartweed as a fly repellent for horses, other than the aforementioned note in the paper. If anyone knows of such a source, or remembers this plant being used in such a way, I would appreciate it if you would contact me.

Trish Martin is a yeararound resident of Mackinac Island, has earned a master's degree in botany from Central Michigan University, and owns Bogan Lane Inn.