Since the 1930s, archaeologists have been accumulating data on the lost crops of eastern North America. These are a group of annual plants (Chenopodium berlandieri, Hordeum pusillum, Iva annua, Phalaris caroliniana, and Polygonum erectum) that were cultivated by Indigenous societies for thousands of years. No published written or oral histories attest to the methods used in their cultivation, and their domesticated forms are thought to be extinct. The potentials and constraints of this agricultural system can only be reconstructed experimentally. We report two experiments designed to investigate germinability, phenology, and yield, which resulted in yield estimates for two of the lost crops, goosefoot (Chenopodium sp.) and erect knotweed (Polygonum erectum). A polyculture of these two crops is more productive than either grown as a monoculture, higher yielding than global averages for closely related domesticated crops, and comparable to yields for traditionally grown maize (Zea mays). We also report several novel insights into germination requirements and phenology for all five lost crops that contribute to a more accurate reconstruction of this crop complex. However, we failed to answer several of our research questions, and instead came away with many new questions. Obtaining seed is merely a necessary pre-condition for raising a crop. Without guidance from experienced cultivators, best practices must be developed over the course of many growing seasons. Experimentation with crop progenitors is necessary to fully understand the dynamics of ancient agroecosystems and their interaction with ecological knowledge systems.