Weed interference in annual cropping systems is highly dynamic in time and space. Favorably positioned plant individuals typically acquire a disproportionate share of contestable resources, thereby suppressing the growth of smaller neighbors. This principle of size-asymmetric competition suggests that driving events occurring early in the growing season, when competition hierarchies are first formed, have an important role in governing yield loss outcomes in annual cropping systems. A two-year (2005, 2006) field trial was conducted with maize (Zea mays L.) grown with high-density stands of four annual weed species (Setaria faberi Herrm., Abutilon theophrasti M., Chenopodium album L., and Amaranthus retroflexus L.) to, (i.) assess the influence of diverse establishment dates and the relative time of crop and weed emergence on the evolution of competition hierarchies, (ii.) quantify the relationship between these hierarchies and eventual maize yield, and (iii.) conceptualize decision rules for adaptive weed management based on assessments of early-season competition intensity. Path analysis identified three system elements that jointly determine the evolution of maize-weed competition hierarchies and crop yield loss: (1) relative onset of the rapid growth phase, (2) comparative stem extension rates during rapid growth, and (3) relative onset of flowering and the termination of stem extension. The most competitive weed stands were co-dominant in the mixed canopy at maize anthesis, and subsequently over-topped the maize with continued height development thereafter. In this scenario, maize yield losses approached 60%. Conversely, weed stands with relatively late onset of rapid growth were typically suppressed in the mixed canopy (i.e. < 50% maize height at maturity), and caused only modest yield losses (ca. 5 - 10%). Growth analysis of weed individuals suggests that the degree of early height disadvantage (ca. 50 cm maize height) is a cross-species predictor of eventual canopy position that may be useful for adaptive weed management.