Autumn sneezeweed is a late-blooming perennial with branching, winged stems. Flowerheads are many, all yellow, with 10–18 ray florets fan-shaped, notched, reflexed downward. The large disk is dome-shaped. Blooms August–November. Leaves are alternate, well-developed along the stem, with the basal and lower stem leaves usually somewhat smaller than the median ones and absent at flowering time; usually oblanceolate to elliptic to lance-shaped, entire or with teeth (often above the midpoint); the leaf tissue extending down the stem as wings.
Similar species: Four heleniums grow in Missouri. Bitterweed and purple-headed sneezeweed have their own entries in this guide. The fourth, Virginia sneezeweed (H. virginicum) is the most like autumn sneezeweed. A state endangered and federally threatened species, it only occurs in about 9 of our southern Ozark counties, primarily in boggy, sinkhole pond habitats. Oddly, the only other populations in the world are in the state of Virginia, and nowhere else. It is found in moister soils than autumn sneezeweed, and its leaves are mostly basal, with the basal and lower stem leaves significantly larger than the middle and upper stem leaves; the basal and lower leaves are usually persistent at flowering time; it blooms July–September.
Height: to 6 feet.
Scattered nearly statewide except Southeast Lowlands and the northwestern section of the state.
Habitat and Conservation
Occurs on banks of streams, rivers, and spring branches, margins of ponds, lakes, and sinkhole ponds, sloughs, fens, and seeps, marshes, bottomland prairies, moist depressions of upland prairies, and bottomland forests; also pastures, ditches, railroads, roadsides, and moist, open, disturbed areas.
Collections made by Julian Steyermark in Howell County in 1960 of unusual but similar plants were long thought to be oddball hybrids of autumn sneezeweed and purple-headed sneezeweed. But in 2000 DNA testing proved they were not descendants of those species and showed instead they were Virginia sneezeweed, until then known only as an endangered plant growing along sinkhole ponds in the Shenandoah Valley. How did this plant come to have such widely separated populations? Apparently they are relict ranges of what had long ago been a single, broad range, before ice-age glaciers split it up, and the populations shrank to their current tiny ranges.
Sneezeweeds were used historically by Native Americans and pioneers as snuff. Inhaling the dried, powdered disk florets caused violent, prolonged sneezing, and people did this as a way of alleviating colds, stuffy noses, headache, and other maladies.
Numerous bees, wasps, flies, butterflies, and beetles visit the flowers for nectar and pollen. Aphids suck the sap, and moth caterpillars bore in the stems. Sneezeweeds contain toxic, bitter substances, and grazing mammals, including cattle, avoid eating them.