Phenological spectra from two adjacent first‐year old fields suggest that phenological events may be directed by the biotic influences of associated species as well as by climatic and edaphic conditions of the region. These two fields possessed similar macroclimatic conditions but had differing soil textures and crop histories. Phenological spectra were developed by observations made on all plant species occurring in fixed quadrats during the duration of this study, April 1, 1970, to October 20, 1970. The phenophases observed were initiation of vegetative growth, time of budding, occurrence of flowering, fruiting sequences, and time of seed set and dissemination. Production studies based on short‐term harvest methods indicated the dominance of Erigeron canadensis in the abandoned soybean field, and Erigeron annus in the abandoned corn field.

Phenological spectra from two adjacent first‐year old fields suggest that phenological events may be directed by the biotic influences of associated species as well as by climatic and edaphic conditions of the region. These two fields possessed similar macroclimatic conditions but had differing soil textures and crop histories. Phenological spectra were developed by observations made on all plant species occurring in fixed quadrats during the duration of this study, April 1, 1970, to October 20, 1970. The phenophases observed were initiation of vegetative growth, time of budding, occurrence of flowering, fruiting sequences, and time of seed set and dissemination. Production studies based on short‐term harvest methods indicated the dominance of Erigeron canadensis in the abandoned soybean field, and Erigeron annus in the abandoned corn field.