Microstegium vimineum (Japanese stiltgrass, JPS) is an annual shade-tolerant grass that has invaded much of the eastern US; its range continues to expand into new environments further west, north, and at higher elevations.  This species is composed of several different genotypes that may help explain its ability to colonize novel sites rapidly.  Some of these genotypes are defined by unique morphological traits, one of which is whether an awn is present on the florets.  Some of our previous research has shown that awned JPS is found at northern latitudes whereas awnless JPS is found at southern latitudes in its native and US invasive range.  We argue that the awn of the awned-type may facilitate burial into soil, buffering the seed against freezing temperatures or that awn presence is linked to cold-tolerance.  However, even if these predictions are supported by future data, they do not explain why the awned type does not appear to be expanding further south. Consequently, we hypothesize that the awnless, southern plants possess traits that give them a competitive advantage over the awned plants.  To test this, we grew 72 second-generation populations (F2) that originated from plants collected from paired dry and mesic habitats, then grown in common greenhouse conditions to produce the F1 generation; F1 seed were then grown to produce the F2 plants and seeds.  We evaluated 21 morphological traits that appeared to be conserved across generations.  We also selected one awned and one awnless type to compete within the same pot, using six replicates.  Our results show that the awnless type has significantly longer tillers, single tillers with greater biomass, larger total shoot biomass, more branches per tiller, more nodes per tiller, longer axillary roots that occur at higher nodes on each tiller, and wider leaves than the awned type. The awned type has more tillers per pot, suggesting a bunched growth habit compared with the awnless type’s sprawling form. The two types do not differ in terms of total chasmogamous (open flowers) inflorescence biomass, but the awnless type produces more seeds while the awned type has heavier seeds. The awnless type takes 1.5x longer to flower, but the seeds of the awned type take 2x longer to mature. These same trait differences are found in the plants grown in direct competition, of which differences in tissue color made the plants easy to distinguish within the same pot. Although the awned plants may be producing heavier seed, the larger plants and higher seed production of the awnless type indicate the awnless plants could dominate when growing in the same area.  The awned plants’ investment in a longer reproductive period may ensure germination and survival in colder climates, whereas the more abundant, smaller seeds as well as a greater capacity to spread vegetatively may ensure rapid colonization in warmer climates by the awnless type. Future research will focus on these different growth habits as well address potential anatomical and physiological differences between plants of the two awn types.