Iva annua var. macrocarpa

(S.F. Blake) R. Jackson

[Steyermark: Iva ciliata Willd.]

Sumpweed, marshelder

Asteraceae (Compositae)

       Sumpweed, like sunflower (Helianthus annuus var. macrocarpus), is a member of the aster family that was domesticated in eastern North America before the introduction of corn. Few people today are familiar with the wild plant (Figure 1), and use of domesticated sumpweed did not survive into modern times. The archaeological record, however, indicates that sumpweed was an important food for some hunter-gatherer-gardeners in the Midwest and Midsouth. Its production apparently declined after A.D. 1200, and early Europeans left no known written descriptions of how it was grown or processed.


       The fruit of Iva annua is an achene that consists of a single seed inside a dry pericarp. The dark brown achenes from wild plants are rarely longer than 4 mm in length. The shape roughly resembles a heart or triangular tear-drop with a narrower, rounded tip or "beak" at one end (Figure 2). Domesticated archaeological Iva annua var. macrocarpa has achenes that vary in color from tan to medium brown and range from ca. 4 to 10 mm in length and ca. 1.5 to 6.5 mm in width (Yarnell 1978). The average length of achenes from some sites exceeds 7 mm. Therefore, wild Iva annua is easily distinguished from Iva annua var. macrocarpa on the basis of size.

       Several features can be used to distinguish between domesticated archaeological sumpweed and sunflower specimens. Sumpweed has beaked, heart-shaped achenes and kernels, both of which frequently have between three and five longitudinal ridges (Figures 4 and 5). Sunflower achenes are obovoid and lack these prominent ridges. Sumpweed achenes and seeds are less elongate (have greater width:length ratios) than their sunflower counterparts. The kernels of wild-sized Iva annua can be wider than they are long (Figure 3).
       Archaeobotanists reporting the sizes of charred sumpweed kernels and/or achenes usually apply a correction factor to adjust for shrinkage due to carbonization.  Asch and Asch (1985:163) developed the following equations to estiimate uncarbonized achene dimensions from carbonized Iva annua kernels:


            Uncarbonized achene length = 1.36 x (carbonized kernel length) + 0.17 mm

            Uncarbonized achene width  = 1.45 x (carbonized kernel width) - 0.06 mm


To estimate uncarbonized achene length and width when dealing with carbonized achenes rather than kernels, both length and width are increased by 10% (i.e., divided by 0.9 or multiplied by 1.1).

Archaeological Distribution

       Domesticated sumpweed specimens have been recovered from sites in the eastern Great Plains, Midwest, and Midsouth, with a late (protohistoric), disjunct record from central North Carolina (Gremillion 1993:382). Recognition of sumpweed as a domesticate began with excavations of dry rockshelter sites in the Ozarks and in Kentucky during the 1920s and 1930s. Gilmore (1931) noted that achenes from stored deposits were much larger than those produced by wild plants, and he inferred they had been cultivated. Jones (1936) found an abundance of large sumpweed seeds in human paleofeces from Newt Kash Hollow Shelter in Kentucky, strengthening the argument for sumpweed's prehistoric dietary significance. Using archaeological specimens from six sites, Blake (1939) formally designated a distinct variety; "an ancient cultivated strain obtained by selection and now extinct." This view is accepted today.

       Sumpweed was domesticated long before maize was introduced into the Eastern Woodlands. An AMS radiocarbon date on charred sumpweed from the Napoleon Hollow site in Illinois documents that size increase resulting from domestication occurred by 2000 B.C. (Asch and Asch 1985). By 1000 B.C., sumpweed was being stored along with sunflower, squash (Cucurbita pepo ssp.

ovifera), and thin-testa chenopod (Chenopodium berlandieri ssp. jonesianum) seeds, all probably set aside for planting (Fritz 1994). Sumpweed seeds and achenes have been recovered from caves and rockshelter deposits dating to the first millennium B.C. and from open sites dating to the first and early second millennia A.D., but the crop apparently declined in importance after the intensification of maize agriculture at about A.D. 1000-1200.

The Modern Plant and Its Distribution

       Sumpweed occurs in the middle and lower Mississippi drainage system and westward onto the plains. It grows in disturbed, treeless habitats, such as river bottoms and wet prairies that flood annually and stay moist throughout the growing season. The mature plan tends to be waist-high or chest-high, lacks showy flowers, and bears its fruits on elongated inflorescences. Sumpweed is hindered by competition with other weeds and tall grasses, but does well in open conditions maintained by mowing or grazing.


       Harvesting experiments using wild stands show that sumpweed holds considerable economic potential. The oily seeds are a concentrated energy source, being high in protein, calcium, iron, phosphorus, potassium, thiamine, and niacin (Asch and Asch 1978). However, for reasons that we cannot explain, sumpweed fell out of favor late in prehistoric times.


Asch, D. L., and N. B. Asch

    1978   The Economic Potential of Iva annua and Its Prehistoric Importance in the Lower Illinois
            Valley. In The Nature and Status of Ethnobotany, edited by R. I. Ford, pp. 301-341.
            Anthropological Papers No. 67. Museum of Anthropology, University of Michigan, Ann

    1985   Prehistoric Plant Cultivation in West-Central Illinois. In Prehistoric Food Production in                    North America, edited by R. I. Ford, pp. 149-203. Anthropological Papers No. 75. Museum
            of Anthropology, University of Michigan, Ann Arbor.

Blake, S. F.

    1939   A New Variety of Iva ciliata from Indian Rock Shelters in the South Central United States.
            Rhodora 41:81-86.

Fritz, G. J.

    1994   In Color and In Time: Prehistoric Ozark Agriculture. In Agricultural Origins and
            Development in the Midcontinent, edited by W. Green, pp. 105-126. Office of the State
            Archaeologist, University of Iowa, Report 19. Iowa City.

Gilmore, M. R.

    1931   Vegetal Remains of the Ozark Bluff-Dweller Culture. Papers of the Michigan Academy of
            Science, Arts, and Letters 14:83-102.

Gremillion, K. J.

    1993   Botanical Remains [from the Jenrette Site]. In Indian Communities on the North Carolina
            Piedmont, A.D. 1000-1700, edited by H. T. Ward and R. P. S. Davis, Jr., pp. 373-384.
            Research Laboratories of Anthropology, Monograph No. 2. University of North Carolina,
            Chapel Hill.

Jones, V.

    1936   The Vegetal Remains of Newt Kash Hollow Shelter. In Rock-Shelters in Menifee County,
            Kentucky, edited by W. S. Webb and W. D. Funkhouser, pp. 147-165. Reports in
            Anthropology and Archaeology 3(4). University of Kentucky, Lexington.

Radford, A. E., H. E. Ahles, and C. R. Bell

    1964   Manual of the Vascular Flora of the Carolinas. University of North Carolina Press, Chapel

Yarnell, R. A.

    1978   Domestication of Sunflower and Sumpweed in Eastern North America. In The Nature and
            Status of Ethnobotany, edited by R. I. Ford, pp. 289-299. Anthropological Papers No. 67.
            Museum of Anthropology, University of Michigan, Ann Arbor.

Written by:  Gayle Fritz, Gina Powell, and Katherine Elson