Ipomoea spp. L.

Morning Glory, Wild Potato Vine

Convolvulaceae

       Ipomoea plants are indigenous to many areas of the world, and several varieties, most notably the tropical species Ipomoea pupurea and I. coccinea, have been spread around the globe as ornamental vines. Characterized by their heart-shaped leaves and large showy flowers, morning glories are commonly grown in gardens across the United States. While rare in archaeological contexts, historical ethnographic studies indicate that the roots of Ipomoea pandurata and I. leptophylla were eaten as cooked vegetables and were used medicinally, predominantly as purgatives.


Description
       Ipomoea seeds can differ widely in morphology between species. Ipomoea lacunosa (Figure 1) displays a common shape for Ipomoea seeds, almost triangular in appearance and cross section. The seeds range from 3.5 to 5 mm in length, and 3 to 4 mm in width, and bear an embryo that is clearly visible at the base of the seed. Seeds of this and several other species have a central division running lengthwise from the embryo, and have a tendency to “pop” open along this division during experimental charring if cooked at a high temperature (above 250º C). Ipomoea pandurata (Figure 2) seeds are much larger (5.5 to 7 mm in length, 3.5 to 5 mm in width) and are surrounded by a seed coat with long (up to 10 mm) hairs around the rim. These seeds are more ovoid in shape and lack the central division of I. lacunosa, although the round embryo (up to 1 mm in diameter) is still visible at the base of the seed. They do not pop open at high temperatures, but the seed coat hairs are fragile and may be absent from seeds recovered in archaeological contexts.
       Plants in the genus Convolvulus have a similar appearance, with the same distinctive flowers and leaves of Ipomoea. However, the seeds of these plants, such as Convolvulus sepium (Figure 3), appear very different. While Convolvulus seeds also have a distinctive embryo similar in appearance to those of Ipomoea, the Convolvulus seeds are somewhat irregular in shape and are covered in small raised bumps, unlike the smooth or hairy surfaces of Ipomoea seeds. Fragments of Convolvulus should appear very different from those of Ipomoea due to this surface texturing. Unless a seed fragment contains only the area right around the embryo, it is unlikely that Convolvulus seeds or seed fragments could be mistaken for Ipomoea in archaeological samples.

Archaeologica Distribution
       Ipomoea seeds are uncommon in archaeological assemblages. They have been found in several areas of the modern range of the genus, particularly in the Middle and Lower Mississippi Valley. They were recovered from several American Bottom sites, including the Robinson’s Lake, Lohmann, and BBB Motor sites, and most often from the Emergent Mississippian period (Johannessen 1984). Thirty-five carbonized Ipomoea seeds were recovered from Feature 7 at the Olszewski Site, a large pit filled with an huge variety and number of seeds dated to the Lohmann Phase (1000-1050 A.D.). These Ipomoea seeds had sprouted, implying that they had been stored for a period of time. This feature may represent remains of a medical or ceremonial occasion (Dunavan 1990). A cache of 57 carbonized Ipomoea seeds was recovered from two pits excavated at the Spoonbill site in northeastern Texas, which was occupied from 800-1300 AD. Several of the seeds from Spoonbill are pictured in Crane’s article (1981), and from the photographs appear to be from Ipomoea lacunosa or a species with a similar seed morphology; they are certainly not I. pandurata or I. leptophylla, and so it is unlikely that this cache represents seeds stored for propagation of the vegetable. According to Crane (1981:86), the pits or seeds possibly represent storage for use as hallucinogens, as several species contain amides of lysergic acid related to LSD. This suggestion is based on ethnographic accounts of the Aztecs eating the ground seeds of I. tricolor as hallucinogens. A large number of carbonized Ipomoea seeds have been recovered from Early and Late Mississippian contexts in the Lower Little Tennessee River Valley in eastern Tennessee. These seeds are associated with the advent and intensification of maize agriculture, and may represent Ipomoea growing as a weed in agricultural fields and gardens (Chapman and Shea 1980:76).

The Modern Plant and its Distribution
       Ipomoea species are twining vines with thin, green stems, heart-shaped leaves, and showy flowers (Figure 4). Native species flower from May to October and leave capsules of seeds. Only two species of Ipomoea are native to Missouri, with twice that number introduced from tropical America. Both of these native species range from Florida to Texas in the south, to Connecticut and New Jersey in the north, and throughout the midwest to Michigan and Iowa. Ipomoea species grow in moist alluvial areas along streams, in wet meadows, and in many disturbed areas, including roadsides and along railroad tracks (Steyermark 1963:1212-1217).

Discussion
       Ipomoea is currently grown around the world as an ornamental climber. Historically, however, the plants were used by Native American peoples in a variety of ways. The large tuberous root of Ipomoea pandurata, which grows up to 11 kilograms in weight, was eaten as a cooked vegetable by historic Indian groups (Steyermark 1963:1216). Carolina Indians used the root for kidney troubles, rheumatism, and as a purgative (King 1984). The medicinal properties of Ipomoea pandurata did not go unnoticed by early American scientists. William Bartram, the famous early botanist, noted that “the dissolvent and diuretant powers of the root... so much esteemed as a remedy for nephritic complaints, were discovered by the Indians to the inhabitants of Carolina” (qtd. in Kindscher 1992:128). Ipomoea leptophylla, native to the prairie habitats of the Great Plains, has a root similar to that of I. pandurata that was roasted in famine periods by the Indians of Montana and Wyoming (Yanovsky 1936). One paleoenvironmental study suggests that Ipomoea pandurata was a common plant in the middle Ohio Valley for much of prehistory (Reidhead 1984).
       Although Ipomoea seeds do not appear frequently in archaeological contexts, if used primarily as a root vegetable and medicinal plant, Ipomoea remains would be less likely to be carbonized and preserved in an identifiable state. The uses of this plant historically suggests that I. pandurata was not a preferred food, but it was a part of prehistoric subsistence patterns, mainly utilized in times of famine.  The medicinal uses of the root were likely similar in the prehistoric period to those documented from more recent times, although it is difficult to say how important Ipomoea might have been in a prehistoric pharmacopoeia. Hallucinogenic use of the seeds could result in carbonized caches, such as that at Spoonbill, but further chemical analysis of North American Ipomoea species is necessary to evaluate that possibility. While relatively abundant in certain habitats, the significance of Ipomoea species in prehistory remains unclear, and certainly could have varied significantly over time and space.

References
Chapman, J., and J. B. Shea
    1981   The Archaeobotanical Record: Early Archaic to Contact in the LowerLittle Tennessee River
            Valley. Tennessee Archaeology 6(1): 60-84.
Crane, C. J.
    1982   Plant Utilization at Spoonbill, an Early Caddo Site in Northeast Texas. Midcontinental
            Journal of Archaeology 7(1): 81-97.
Dunavan, S. L.
    1990   Floral Remains. In Selected Early Mississippian Household Sites in the American Bottom,
            Part 5-The Olszewksi Site (11-S-465), by J. K. Douglas. University of Illinois Press, Urbana
            and Chicago. pp. 389-403.
Johannessen, S.
    1984   Paleoethnobotany. In American Bottom Archaeology: A Summary of the FAI-270 Project
            Contribution to the Culture History of the Mississippi River Valley, edited by C. J. Bareis and
            J. W. Porter. pp. 197-214. University of Illinois Press, Urbana.
Kindscher, K.
    1992   Medicinal Plants of the Prairie: An Ethnobotanical Guide. University Press of Kansas,
            Lawrence.
King, F. B.
    1984   Plants, People, and Paleoecology: Biotic Communities and Aboriginal Plant Usage in Illinois.
            Illinois State Museum Scientific Papers, Vol. 20. Illinois State Museum, Springfield.
Reidhead, V. A.
    1984   A Reconstruction of the Presettlement Vegetation of the Middle Ohio Valley Region. In
            Experiments and Observations on Aboriginal Wild Plant Food Utilization in Eastern North
            America. edited by P. J. Munson. pp. 386-426. Indiana Historical Society Prehistory
            Research Series, Vol. 6, No. 2. Indiana Historical Society, Indianapolis.
Steyermark, J. A.
    1963   Flora of Missouri. Iowa State University Press, Ames.
Yanovsky, E.
    1936   Food Plants of the North American Indians. U.S. Department of Agriculture Miscellaneous
            Publication 237.

Written by: Mac Marston