Answer: There are many different plants you could use as a groundcover depending on the growing conditions in your back yard and why the area is currently bare. If it is shady you might look at Vinca minor, Liriope, or Hedera helix. If it is shady and damp, you could try Pachysandra or lily of the valley. If it is partly sunny you might try Ajuga, Liriope, or Vinca minor. If it is sunny, you might try a sedum or creeping thyme, creeping phlox (Phlox subulata) or a low growing ornamental grass such as Pennisetum alopecuroides 'Little Bunny' or a low growing juniper shrub. Your local professional nursery staff should be able to help you analyze the growing conditions in your back yard and suggest plants that would thrive there.
Turf grass varieties are also selected based on the growing conditions, whether it is sunny or shady and at what time of day, whether the soil is particularly wet or dry or average, what kind of soil it is, the fertility levels, and so on. I would suggest you consult with your local county extension for assistance in developing a lawn establishment and maintenance program. They will be able to help you with the required soil testing as well as selecting the best grass to use. (They may also have ground cover suggestions.)
In the meantime you may find the following lawn care information helpful. You will notice the first topic listed is choosing the right grass. You may need to cut and paste the complete url into your browser to make it work correctly.
I hope this helps!
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