Differences among plant species in morphology and patterns of growth are assumed to influence their ability to acquire resources and, consequently, their competitive ability. Despite the acknowledged importance of below-ground resources for plant growth, our knowledge of species differences in root morphology of non-agricultural plants is limited. Comparisons of root morphology, growth rate and topology of seedlings of 12 herbaceous plant species that occur in early to mid-successional fields revealed significant differences among species that were largely related to life history. Annuals grew faster and produced longer and more branched roots than did biennials and perennials. Only among the annuals was there a positive correlation between seed mass and root growth. The grasses allocated proportionately more biomass to roots than the dicots, but did not differ in root length or branching pattern. As seedlings, all 12 species exhibited a herringbone topology; although after 10 d there were significant differences in topology between annuals and perennials indicating that the annuals had begun to develop a more dichotomously branched root system. The possible effects of early differences in root morphology among life-history types in acquiring soil resources in heterogeneous and successional environments are discussed.