Ground cover species are a diverse group of small, low-growing plants. A high diversity of plant species is important because it means that more wildlife is supported and that the ecosystem is better able to resist disturbances such as invasive species and disease. Ground cover benefits the Preserve ecosystem by holding soil in place and providing habitat and food for birds, small mammals, insects, and other species. Insects also use ground cover plants to hide from predators, to wait for passing prey, and as a surface for eggs.

Common ground cover plants found in the Bull Creek Nature Preserve include grasses, sedges, vines, ferns, succulents, and wildflowers. Grasses and sedges are small, non-woody plants with narrow leaves. Vines are plants with a climbing or creeping stem that use other plants for support. Ferns are flowerless, seedless plants, often with featherlike fronds. Succulents are water-storing plants such as cacti and yucca that are adapted for dry climates.

Wildflowers are a forb, which is a small, non-woody plant other than grass. Common plants considered weeds, such as clovers and dandelions, are forbs as well. Besides contributing to the heritage and natural beauty of the region, wildflowers provide food for insects and birds. For example, wildflowers produce an abundant supply of seeds for granivorous (seed-eating) birds, including the painted bunting and the Carolina chickadee. They also attract insects that are preyed upon by insectivorous (insect-eating) birds, such as the golden-cheeked warbler.