By Julianne Powers – Lab Archaeologist & CART Archeobotony
When archaeologists dig, they often take soil and floatation sample in addition to looking for artifacts. These are usually close to a gallon in volume (think the size of a gallon of milk). Samples are taken when we find a feature, like a cellar, well or trash pit. We take some samples that are pushed through window screen mesh with water. Some samples go through a floatation machine. The machine is full of moving water that causes rocks and heavy artifacts to sink to the bottom while organic matter (such as roots, sticks, and seeds) floats to the top. This lighter matter floats over the edge of a wall like a waterfall, then is caught by finely woven cloth. From there, we let it dry and then look through it with it with tweezers to pull out botanical remains such as seeds and charcoal.
Finding seeds can tell us what people were eating at the time the feature was filled. For example, if we find lots of cherry pits in a kitchen midden, the people who lived there were probably eating cherries and throwing the pits into the trash pile. Seeds can also tell us what trees or plants were growing nearby. When we find burned seeds, we might assume that these were cooked in some way or near a fire. If we find burned pumpkin seeds, the people of the time may have roasted them to eat as a snack when a few fell into the fire.
Most of our light fraction floatation is sent to archeobotonist Justine McKinght who specializes “in the analysis of plant macro-remains from Prehistoric and Historic archaeological sites across the Eastern Woodlands of North America.”  From the samples we send, Justine McKnight can tell us what trees and plants might have been growing in Colchester!
Justine also studies the charcoal we find, she can see parts of the tree like pores and rings that help her identify what species the tree is. At one of our sites, she found charcoal from white oaks, red oaks, hickory, yellow poplar, American chestnut, maple, black locust and elm. Using this data, we know what types of trees were shading the residents of that site and what trees they might have been using to build their homes.
 McKnight, Justine. Justine Woodard McKnight Archeobotonical Consultant. http://archeobotany.com Accessed July 31, 2014