Fragaria spp.

Fragaria spp. – Strawberry

Rosaceae

Figure 1. Scanning Electron Micrograph (65x) of uncarbonized Fragaria virginiana.

The small, plump achenes of the strawberry plant are not often recovered in archaeological contexts, as they are consumed along with the flesh and therefore are rarely carbonized. Paleofeces containing strawberry remains have been recovered from Salts and Mammoth Caves in Kentucky (Gremillion and Sobolik 1996), and uncharred achenes have been found in the small fractions (<1mm screen size) of bulk samples from submound 51 at Cahokia in Illinois (Fritz 1997; Pauketat et al. 2002). The seeds of Fragaria species are similar in size and shape to those of Duchesnia indica, the false strawberry, therefore special attention is paid to methods of differentiating among the various species of Fragaria and D. indica.

Description

The edible flesh of the plant is not the “fruit” in the true botanical sense: it is the accessory fruit, the large, fleshy receptacle of one flower. The hard seed-like objects on the outer surface are individual achenes, and are the true fruits of the strawberry. These achenes are light brown to dark pink and somewhat shiny, displaying a finely reticulated surface that is best seen using scanning electron micrography (see Figure 1). This reticulation is most prominent on the dorsal surface, but pronounced ridges protrude from the hilum on the ventral surface, possibly obscuring any reticulation present. The achenes are roundedly triangular and somewhat oblong, with a small indentation at the hilum. The length of uncarbonized F. virginiana Duchesne (Virginia strawberry) specimens ranges between 1.05 and 1.30 mm, with widths between 0.80 and 1.15 mm* . The woodland strawberry, F. vesca L.var. vesca Porter ranges from 1.1 to 1.3 mm long and from 0.7 to 0.9 mm wide. Duchesnia indica, the false strawberry, is on average somewhat smaller, being approximately 1.0 mm long and  0.5-0.6 mm wide.

Figure 2. Light microscope photograph of uncarbonized achenes from F. virginiana.

F. virginiana can be distinguished easily from F. vesca var. vesca (woodland strawberry) if the achene is clean and well preserved. F. vesca var. vesca is similar in length to, but on average significantly thinner in ventral aspect than, F. virginiana, and the “nose” of the achene is pointier and more pronounced as the tip angles up (toward the ventral side). The hilum is thinner and less rounded, and extends further towards the “nose” in the woodland strawberry. Surface ornamentation can also aid in identification. F. vesca var. vescapossesses slightly darker veining, noticeably present over the entire achene body, while the veining in F. virginiana radiates from the hilum and does not extend far across the body. D. indica is characteristically a dark pink-red color when uncharred, and the reticulation is deeper and more regular, occuring over the entire achene. The hilum is not raised above the ventral surface, as is discernable in the true strawberry, and there are no ridges emanating from the hilum. There is a slight concavity on either side of the hilum, and the dorsal edge is more rounded in profile than that of Fragaria specimens.

Fragaria are also similar in shape to Potentilla spp. (cinquefoil). Fragaria achenes are generally smaller than Potentilla and are more rounded in top view – Potentilla is characterized by having one side that is straight, or even concave, and one rounded side.

Archaeological Distribution

Strawberries are assumed to have been eaten fresh, and, owing to their restricted fruiting season (late spring to early summer), are employed in palaeoethnobotanical studies as indicators of seasonality. For example, strawberry seeds were found in the fecal remains recovered from Salts Cave and Mammoth Cave, Kentucky, in association with maygrass and blackberry (a late summer fruiting taxa) (Gremillion and Sobolik 1996). In this instance, the presence of Fragaria remains led the investigators to conclude that the maygrass was not stored for winter use but was consumed in the summer months. Fragaria seeds and those of other fleshy fruits were found in abundance in 15 Iroquoian sites in Ontario, leading the researcher to conclude that “the importance of non-cultigens to the Iroquoian diet has been greatly underestimated” (Ounjian 1998)  Remains of the strawberry are so seldom encountered in paleoethnobotanical investigations that a clear view of its prehistoric distribution is not available at present.

The Modern Plants and their Distribution

Strawberry plants commonly reside in fields, on open slopes, and at the edges of woodlands, where sunlight is direct. They are most productive in soil that is fertile, well-drained, and moisture retentive (Gray 1970). This plant produces white flowers and small (up to 20 mm in diameter), sweet, and succulent red fruits. F. virginiana flowers from April to May, and the fruits ripen in late spring/early summer. The Virginia Strawberry, F. virginiana, is found throughout eastern North America, from Newfoundland to Minnesota, south to Florida and Oklahoma. F. vesca var. vesca, the woodland strawberry, is found in the north from Newfoundland to Michigan, south to West Virginia. F.vesca L. var.americana Portercan be found in Canada from Quebec west to northern Alberta south to Mew Mexico and Missouri (Steyermark 1963).

Domestication and Taxonomic Considerations

The modern domesticate, F. ananassa, is a hybrid of F. virginiana and F. chiloensis (the garden strawberry), and its large “fruits” bearing sunken achenes resemble the virginiana type moreso than they resemble the chiloesis variety (Gray 1970).

Disucssion

Both biomedicine and Native American traditional medicine value the fruits and leaves of this plant. The berries contain antioxidants, chemicals that ameliorate oxidative stress (associated with heart and lung diseases and cancer), and strawberry extracts have been found to reduce age-related neuronal decrements (Cao et al. 1998).
The plant has been identified in the ethnobotanical literature as possessing abortifacient, analgesic, diuretic, and anti-diarrheal properties, and, owing to its Vitamin C content, strawberries were once given as daily rations to sailors to prevent scurvy (Moerman 1998). The tea made from dried leaves is used for therapeutic purposes or to supplement supplies of the commonly consumed tea leaf varieties.

 

Written by: Sarah Walshaw

*The measurements for F. virginiana  and F. vesca were taken using seeds (n=10 per species) made available through the generosity of Alwynne Beaudoin at the Provincial Museum of Alberta. Duchesnia indica specimens were sampled from the collection of the Paleoethnobotany Laboratory at Washington University.

References

  1. Cao, G. H., R. M. Russell, N. Lischner and R. L. Prior
        1998   Serum antioxidant capacity is increased by consumption of strawberries, spinach, red wine or vitamin C in elderly women. Journal of Nutrition 128(12):2383-2390.
  2. Fritz, G. J.
        1997   Special Plants from Early Cahokia. Paper presented to the 54th Meeting of the Southeastern Archaeological Conference, Baton Rouge.
  3. Gray, A.
        1970   Gray’s Manual of Botany. 9th Edition. New York: Van Nostrand.
  4. Gremillion, K. J. and K. D. Sobolik
        1996   Dietary variability among prehistoric forager-farmers of eastern North America.Current Anthropology 37(3):529-539.
  5. Moerman, D. E.
        1998   Native American Ethnobotany. Portland: Timber Press.
  6. Ounjian, G. L.
        1998   Glen Meyer and Prehistoric Neutral Paleoethnobotany. Unpublished Ph.D. dissertation, Department of Anthropology, University of Toronto, Canada.
  7. Pauketat, T. R., L. S. Kelly, G. J. Fritz, N. H. Lopinot, S. Elias, and E. Hargrave
        2002   Residues of Feasting and Public Ritual at Early Cahokia. American Antiquity 67 (2):357-279.
  8. Steyermark, J. A.
        1963   Flora of Missouri. Iowa State University Press, Ames.