The interactions between plants that determine competition and coexistence are strongly influenced by their fine-scale spatial pattern. These interactions also ultimately influence diversity, function, and structure in plant communities. In areas that have undergone extensive land-use or anthropogenic degradation, such as North American grasslands, there is a critical need to understand how spatial patterning of plant species can be manipulated to maximize diversity and restoration success. The research presented in this thesis employed a novel planting strategy using conspecific patch sizes at seeding to spatially manipulate inter- and intraspecific interactions among native grassland plant species. I found that seeded patch size had strong effects on diversity maintenance, biodiversity effects, productivity, and invasion, and that the typical uniformly mixed seeding approach in biodiversity ecosystem function studies and restoration applications may not maximize these responses. Smaller patch plots tend to have strong selection effects from dominant forb species, although this may change over time. Additionally, there were species-specific and plant functional group-specific responses to patch size that should be considered in restoration of low-diversity sites. The initial fine-scale plant pattern of had measurable effects on the spatial abundance of species, functional groups, and invasion. Finally, I found that initial patch size had strong effects on the abundance several insect families that are ecologically relevant. Furthermore, the abundance of arthropod herbivores, parasitoids, and predators were significantly influenced as well, with variable relationships to patch size. These findings help to further our understanding of how plant species spatial pattern affects biodiversity, ecosystem functioning, and community structure, as well as provide novel ideas for planting strategies in grassland restoration.