Plant Harvesting

Wild plants, such as geophytes, were an important part of the native diet in the past. Geophytes are plants that have edible underground parts, such as bulbs, roots, or tubers. These were a critical source of carbohydrates, just like potatoes and carrots are today. Geophytes found by archeologists at the Waco Lake sites include camas and groundnut. In the wild, these plants grow in dense patches in fertile valley bottoms, making them easy to dig and collect in large quantities. These plants had to be cooked for a long time to make them digestible, nutritious, and sweet tasting. To do this, native peoples dug shallow pits, lined them with rocks, and built a fire over the rocks. After the fire died down, the hot rocks and coals were covered with green "packing" material—prickly pear pads or grass—to keep the food clean and moist. The tubers or bulbs were then placed in the pit and covered with another layer of grass or cactus pads. Finally, the pit was covered over with rocks and dirt to seal in the heat, and the slow cooking process began. Archeologists have found the remains of many such earth ovens in the Waco Lake area.

Why Plant Foods?

Archeologist believe that increased population densities during the Archaic period resulted in “packing” of the landscape. This in turn led to broadening of the diet, including the increased use of plant foods. The use of plant foods also depends on the productivity of the land. Net above-ground plant production for the Waco Lake area is estimated at 1,500 grams (a little more than three pounds) per square meter per year, indicating that hunter-gatherers could have obtained nearly 50 percent of their subsistence from plant gathering. Geophytes are one type of plant food that became a focus of subsistence in the region, and evidence of this was found at the Britton, McMillan, and Higginbotham sites. Camas bulbs and groundnut tubers were identified at McMillan and Higginbotham. Unidentified bulb fragments also were recovered at the Britton site.

There are many historic accounts and ethnographies documenting the importance of camas (Camassia quamash) and groundnut (Apios americana) in the diets of native groups of in the Pacific Northwest and eastern United States, respectively. The cultural, social, and economic significance of these plants cannot be overemphasized as native populations actively managed their habitats. Both types of geophytes are documented in the archeological record of their respective regions, with the use of camas extending further back in time than groundnut based on dated contexts. Another species of camas (Camassia scilloides) and the same species of groundnut are native to Texas, although their current distributions are restricted and their occurrence is common to rare in these areas. Although camas and groundnut can grow in various settings, they flourish in seasonal wetlands, swales, backswamps, and other topographic depressions in bottomlands or riparian zones. Camas and groundnut have low drought tolerance, can withstand shade, and thrive where precipitation ranges between 71 to 140 cm (28 to 55 inches) annually with early spring moisture being most crucial.

Camas

Several studies provide information on the composition and nutritional values of camas and groundnut. Raw camas contain small percentages (less than 10 each) of various fibers, protein, reducing sugars, and several minerals, and high percentages of moisture and inulin. The key dietary ingredient is inulin, a polysaccaride (carbohydrate composed of many chains of simple sugars) containing at least 30 fructose units per molecule. However, humans cannot digest it in its raw state. James Konlande and John Robson’s 1972 study of camas shows that cooking hydrolizes most, if not all, the inulin into fructose (sugar) thus providing an available carbohydrate.

Archeologist Alston Thoms has conducted considerable research on production requirements of camas, and this data is used to examine production potential for the lower Bosque River basin. If considered a staple food, a typically productive camas meadow could yield enough bulbs (1,000 kg/2.7 hectares) to provide a family of five about 20 percent of their caloric intake for the year. It would take approximately 28 days to harvest the annual yield given a rate of 41 kg per person per day. Based on growth models, an effective camas harvest could occur once every five years within a given patch. Given our estimate of 214 people occupying the river basin (see Population Assumptions), the amount of camas needed to support the population can be projected. The number of people (n = 214) converts to 43 family units (one family unit = 5 people) who would have required 43,000 kg of camas per year.

Geophytes would have flourished along the riparian corridors, which cover 23,490 hectares (58,000 acres). Under ideal conditions, this amount of acreage could have produced millions of kilograms of camas bulbs. For 214 people, even 10 percent of this amount represents more than an adequate annual supply. Recalculating the production capability of camas within the context of Lewis Binford’s (2001) minimal group size of 18–20 people, around 10 to 11 hectares would have been needed to generate enough camas in caloric terms for the group for one year. Even if a 10- to 11-hectare camas patch could have produced effective yields only once every five years for a group of 18–20 people, there were potentially more than enough resource patches of this size in the basin to accommodate the estimated 11 to 12 groups (or 214 people). As dense and productive as camas patches can be, it would have been relatively easy for the group to produce a surplus. Whether this ever occurred, however, is not known, as it may have required storage and transport technologies that were deemed too costly (or too labor-intensive for the payoff) and therefore avoided.

Groundnut

Another geophyte, groundnut, is a prolific plant high in carbohydrates and rich in protein, thus providing the primary nutrients one would also receive from camas and deer meat. Elias Yanovsky and R.M. Kingsbury’s 1938 analysis of a fresh groundnut tuber indicates approximately 53 percent is carbohydrates, consisting of non-reducing and reducing sugars, starch, and hemicellulose, a polysaccaride that is more complex than sugar. Dried tubers are 17 percent protein and 5 percent ash. More recent nutritional studies at Louisiana State University report an 11 to 14 percent crude protein content for the tubers on a dry defatted basis, while The Plants for a Future database indicates that a fresh tuber contains 17 g of protein per 100 grams of food. Groundnut also contains protease inhibitors, compounds known to interfere with certain enzymes’ ability to break down proteins. Although documented as eaten raw or cooked, fresh tubers are reported to be viscous (latex consistency) and unsavory, whereas cooking renders them sweet and palatable. An analysis by Michael Ameny and Paul Wilson at Lousiana State University demonstrated that cooking also destroys the protease inhibitors in the tuber, but produces no significant difference in the protein content.

Several accounts note the ease with which groundnut tubers may be collected. The tubers are found a few centimeters below ground and grow in a chain similar to a pearl necklace. In the wild, a plant can yield at least 1 kg of tubers after two years’ growth, and harvests of up to 2.3 kg per plant have been documented by researchers such as Steven Foster and James Duke. Planting densities range from 2,700 to 10,000 plants per acre. To meet a recommended daily intake of 50 g of protein, an individual needs nearly 300 g of groundnut per day, which can easily be harvested from a single plant.

All of these estimates substantiate the view that the riparian zones of the lower Bosque basin could yield substantial amounts of nutrient-rich geophytes, such as camas and groundnut, even with packing of the environment. Thoms has noted that procurement and storage costs for camas are low in the Pacific Northwest, but processing costs are high. High costs appear to be a natural part of geophyte processing and this probably was no different for the hunters and gatherers in the lower Bosque basin, particularly when one considers the significant amounts of rocks, packing materials, and firewood needed to process them. These processing costs, however, could have been offset by the prolific yields of camas and groundnut patches, and by camping near these patches in localities that also provided sufficient amounts of rocks, packing materials, and firewood. This suggests that those chiefly in charge of collecting and processing geophytes—namely women—were also probably the determining voice regarding campsite location.