Arable Plant Communities
Our knowledge of past arable weed communities in crop fields is largely drawn from the study of carbonised seed recovered by excavation. With the exception of the grain storage pit, which is a quite specific feature that also encompasses debates concerning harvesting methods, other features which yield carbonised seed can almost be regarded as random depositories, the seed found being fortuitous. See the paper: Provenance of Carbonised Seed.
Discussion of the origin of carbonised seed, whatever the context, requires there be some understanding and knowledge of the weed community where crops are grown. Subsequent transfer processes involved in, for example grain handling, form part of the discussion relating to the Provenance of Carbonised Seed (see link above). Those discussions incorporate arguments about the effect of cereal height, in relation to climbing weeds especially, and to harvesting methods. The study of the weed community therefore has to reflect these probable interactions.
It is most improbable that, for the majority of farming practices, the entire field weed population will be reflected in any secondary recovery after harvest, whereas growth of the cereal in the face of competition from field weeds will be reflected in yields. See the page Potential Yields of Prehistoric Cereals.
In consequence, the arable weed flora occupying the crop fields at the Ancient Farm were recorded annually. It was appreciated that this would not give a complete picture of the weed flora of 2500 years ago, since a number of weeds are known to have become extinct, with others virtually so. Nonetheless, these studies gave an important insight into the number and frequency of the types of plant likely to have been present on the chalky soils.
Interesting occurrences of ground hugging varieties like the fluellens (Kicksia elatine and K. spuria) have arisen. While arguably native, these do not occur in the archaeological record, which probably reflects the fact that they are unlikely to make the transition from the production area to the settlement area (the commonest source of archaeological data). Whereas the cereal will have had to compete with such weeds for sustenance, the weed height and habit, relative to the crop, is likely to be the determinant in any transfer process.