Horseflyweed is a perennial legume growing on erect, smooth, succulent branching stems with ultimate size of 2 to 4 feet high.
The leaves are tripartite and alternate, with oblanceolate stalkless (or with very minute stalks) 1 inch long leaflets that have bluntly pointed tips and smooth margins, and a gray-green color on the upper side, the entire leaf on a short stalk. The leaf underside is paler in color, showing a fine vein network between the lateral veins. There is a pair of small stipules at the base of the leaf stalk. Leaves appear about one month before the flowers. Leaves turn black upon drying.
The inflorescence is a loosely constructed terminal raceme of a few flowers at the top of stems above the leaves. Each plant can have numerous racemes.
The flowers are perfect, to 1/2 inch long (smaller than other Baptisias) and are on short stalks with corollas in bright yellow, but like most Baptisias, there can be significant variation in color. The green calyx is tubular with 5 pointed lobes while the corolla forms a pea-type flower consisting of 5 petals with the large banner petal turned upward with a notch at the center, and the sides reflexed backward. There are two lateral petals projecting forward which enclose the two keel petals that are usually of a lighter shade, which in turn, house the reproductive parts, which include 10 stamens with yellow anthers and a single style.
Seed: Fertile flowers produce a small elliopsoid shaped inflated seed pod about 3/4 inch long, with a strong ridge line, and with the calyx firmly attached to the flower stalk at one end, but separated on the stalk from the pod itself, and the remains of the style at the other. The pod is green at first then turning black at maturity. The pod contains a number of brown kidney shaped seeds which are loose in the pod when mature (causing a rattle - hence one of the alternate names of Rattleweed). The pod splits open along its ridge line at maturity to release the seeds by wind or bird dispersion. As the stems and racemes become somewhat woody, pods frequently over-winter and provide winter interest. Seeds can be germinated in the spring after cold storage and stratification, but not all will be viable.
Toxicity: See notes at bottom of page:
Habitat: Horseflyweed grows in mesic to dry soils in full sun, but accepts partial shade. There are few pests. The root system consists of a stout brown to black rhizome, yellow inside, and fibrous side roots. Once established, plants will last for years. Baptisias tend to be shrubby with a well developed root system, so plant it where it won't interfere with more formal plants and where you don't have to move it as Baptisias do not like being moved. As a legume it fixes nitrogen in the soil.
Names: The common name of Horseflyweed comes from the old folk use of tying bunches of the plant to the harness of horses where it was said to repel horseflies. The genus name Baptisia is from the Greek word bapto, meaning 'to dye' as a dye can be made from the plant but it is inferior. The species name tinctoria, also means 'used in dying'. The author name for the plant classification, [following the original work of Linnaeus ( the 'L.")], ‘R.Br.’ is for Robert Brown (1773-1858), Scottish botanist for whom ‘Brownian motion’ is named, and who provided names and descriptions of various plant families and was the first keeper of the Botanical Dept. of the British Museum.
Comparisons: A similar plant is False Blue Indigo, B. australis, but there the plant is less branched, the flowers blue, the leaves larger and the pod bigger. The False White Indigo, B. alba, which has white flowers, larger leaflets, is branched, and is a taller plant with the flower raceme held higher with many more flowers and much larger seed pods.
Above: The inflorescence is a loose raceme with individual flowers on long stalks. These appear at the growing tips of the branches. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: The calyx is short with 5 pointed lobes which reflex when the flower opens.
Below and Above:The typical pea family flowrs have an upright banner petal, notched at the center, whose wings reflex back. Two lateral petals project forward completely enclosing the two keel petals.
Below: The tripartite leaf is smaller than other Baptisia's and pale in color on the underside.
Below: The pods are much smaller than other Baptisia's and the remains of the calyx is separated from the base of the pod.
Below: The mature seed pod is blackish in color. The seeds are ovoid with a beak at one end and will turn dark brown when fully mature.
Below: A root section of a young plant.
Eloise Butler introduced Horseflyweed to the Garden in 1913 with plants obtained from Kelsey's Nursery in North Carolina. Martha Crone planted it in 1950 with plants from Lounsberry in Ashford, IL, and 1951 with plants from Robbins Blue Ridge Nursery, and sowed seeds in 1953. Horseflyweed is native to a triangular section of the entire eastern U.S. from the coast inward, starting with Georgia in the south then Northwestward to Tennessee, Illinois and Iowa and Wisconsin. It is not considered today to be native to Minnesota as there was only one historical collection of the plant from Lake City MN in 1882. It is also known in Ontario.
Only two species of Baptisia are considered to be native to Minnesota: B. bracteata, the Plains Wild Indigo and B. lactea, Wild White Indigo. Both of these on listed on the DNR Special Concern List due to habitat loss. The other indigos, B. australis, False Blue Indigo and this species, B. tinctoria, are not considered native to the state.
Toxicity: Animals can be poisoned but typically find B. tinctoria unpalatable due to the presence of the alkaloid cytisine and the acrid poison baptisine. In humans, eating shoots just turning green will cause dramatic purgation, and plant foragers should be aware that young shoots of the Baptisia's resemble Asparagus shoots. These shoots have also been known to poison browsing cattle. Nevertheless, humans have used the bark of the root for medicinal purposes as and antiseptic and stimulant and purgative. (see Hutchins, Ref. 12). It is also used for colds and flue but those herbalists who do use the root tend to make tinctures in combination with other herbs such as Echinaceas and Joe-Pye Weed. Even they consider it too strong by itself.
Uses: All parts of the plant will yield a blue dye but it is inferior to the true indigo, Indigofera tinctoria L.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"