Marshelder or Sumpweed

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Marshelder (Iva annua var. macrocarpa)

Marshelder also called sumpweed, is a member of the aster family. The domesticated var. macrocarpa is extinct, but the wild variety of the plant still thrives. Today, wild marshelder grows on open, moist, and recently disturbed ground in the flood plain of southern Iowa. Flowering occurs in August, and seeds ripen in October. The flowers are borne compactly on several spikes, and harvesters can easily strip the seeds from the spikes.

Marshelder appears in the Upper Midwest as a domesticated plant over 4,000 years ago. Prehistoric people developed wild marshelder into a domesticated variety with larger seeds and greater yields. The size of the seeds increased about 1,000 percent as the result of domestication.

The earliest specimens in Iowa reported as possible cultigens come from a Late Archaic context at the Sand Run West site (13LA38) in Louisa County and at site 13CT228, a Terminal Archaic or Early Woodland site in the Turkey River valley dated to 2,600 years ago. Native people in Iowa grew marshelder into the Late Prehistoric period although its use apparently declined following the introduction of maize. There are no historic descriptions of how it was grown or processed.

Marshelder is similar to wheat in that it needs to grow in large amounts in dense stands in order to produce a sufficient crop to be harvestable. The oily seed is covered with a thin, dry pericarp (protective covering) that is difficult to remove. The seeds are a concentrated energy source— high in protein, calcium, iron, phosphorus, potassium, thiamine, niacin, and B-complex vitamins. Its has been discovered mixed with other oily seeds such as squash and sunflower in Late Prehistoric Glenwood storage pits at sites such as Johnson Farm (13ML129) and Kuhl (13ML138) in Mills County. Researchers suggest that the inhabitants at these sites may have used these plants interchangeably, were storing them together for seed, or perhaps had been mixing them to prepare a type of prehistoric succotash.

Major References

Asch, David L. and William Green 1992
Green, William and Shelly Gradwell 1995
Lopinot, Neal H. 1987

Map of Iowa with olive dots that indicate prehistoric sites known to have cultivated sumpweed

Iowa Sites
Site Number Major Reference Family Genus and Species Iowa Culture
13CK15 Jones, 1993 COMPOSITAE or ASTERACEAE Iva annua var. macrocarpa MC
13CT228 Asch and Green, 1992 (Green) COMPOSITAE or ASTERACEAE Iva annua LA/EW
13LA12 Dunne, 2002 COMPOSITAE or ASTERACEAE Iva annua var. macrocarpa MW/ELW
13LA38 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua LA/MW
13LE110 Zalucha, 1999 COMPOSITAE or ASTERACEAE Iva annua var. macrocarpa O
13LE117B Zalucha, 1999 COMPOSITAE or ASTERACEAE Iva annua var. macrocarpa ELW
13MA207 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua O
13MA209 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua macrocarpa O
13ML129 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua G
13ML130 Adair, 2010 COMPOSITAE or ASTERACEAE Iva annua G
13ML131 Adair, 2010 COMPOSITAE or ASTERACEAE Iva annua G
13ML136 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua G
13ML138 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua G
13ML139 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua G
13ML361 Green and Billeck, 1993 COMPOSITAE or ASTERACEAE Iva annua var. macrocarpa G
13PM1 Adrain, 2003 COMPOSITAE or ASTERACEAE Iva annua MC
13PM25 Asch and Green, 1992 COMPOSITAE or ASTERACEAE Iva annua GO
13WD88 Dunne, 2005 COMPOSITAE or ASTERACEAE Iva annua GO

 

Key
LA Late Archaic
EW Early Woodland
MW Middle Woodland
ELW Early Late Woodland
GO Great Oasis
MC Mill Creek
G Glenwood
O Oneota

Two photographs of marshelder or sumpweed

Two photographs of marshelder or sumpweed

 

Image Credit:
Larry Allain @ USDA-NRCS PLANTS Database
Jeff McMillian @ USDA-NRCS PLANTS Database
Melanie Riley and Mary Kathryn Rocheford, OSA (map)