Field experiments were conducted to determine the growth, development, and seed yield response of scentless chamomile when planted at various dates throughout the growing season. Scentless chamomile emerged within 6 to 15 d of planting and required 75 to 131 growing degree days (GDD). Flowering occurred within 56 to 82 d of planting and required 584 to 845 GDD. Plants that emerged in mid-July and onward did not flower in that season but survived as winter annuals. Spring-planted scentless chamomile matured within 97 to 127 d and required 906 to 1,176 GDD. Plants that emerged in May and June attained more leaf area and biomass than plants that emerged in mid-summer. Plants that emerged early in the growing season produced three-to fourfold more seed than plants that emerged at later dates. Scentless chamomile seed production ranged from 71,000 to 256,000 plants−1 depending on planting date and existing environmental conditions. Results are discussed in terms of its potential to become an increasingly troublesome weed in crops of the Canadian prairies and possible management strategies for its control.