Ask Mr. Smarty Plants

From our Native Plant Database, here are the Propagation Instructions for Sorghastrum nutans (Indiangrass):

Propagation Material: Seeds
Description: Propagate by sowing unstratified seed in fall or stratified seed in spring. Sow 1/4 deep. Division of older plants is difficult because of a dense, tangled root system.
Seed Collection: Collect seed in fall.
Seed Treatment: Seeds require dry stratification.
Commercially Avail: yes
Maintenance: Indian grass tolerates imperfectly drained soil. It is a good accent plant, however it needs tall companions to remain upright.

You will notice it says division of older plants is difficult, which means getting sod plugs would also be difficult. You are probably right that you would get quicker coverage by seed, but "choking out" strangers is not one of the benefits. No matter how carefully you clean and prepare your ground for seed, there are going to be other grass seeds also waiting for their chance to sprout. They will likely be natives to your area in northwestern South California, as is the Indiangrass. They will be just as acclimated to the climate, soil and rainfall of your area as the seed you purchased, and have been brought there by wind, animals and birds. All the grasses tend to look very similar when they first emerge.  Never mind trying to find a spray that will kill everything but the Indiangrass. There are three kinds of herbicide sprays: wide spectrum, which will kill everything green it lands on; broad-leaf plant (or dicot) herbicide which won't kill the Indiangrass, but won't kill the other grasses either, and monocot herbicide which will kill the other grasses and the Indiangrass. Pulling out the grasses you don't want, or even mowing them very low, if you can do that without damaging the grasses you want, will keep the unwanted plants from seeding. But mostly they have to be pulled, again, before they go to seed. Slowly, the grass you want will cover the area sufficiently, but it's going to take a while.

On the subject of establishing a native meadow, which we think is a wonderful idea, read our How-To Articles Meadow Gardening, Butterfly Gardening and Wildlife Gardening. If you want some more grasses for your garden, go to our Native Plant Database, and using "Combination Search," select South Carolina (state, of course) and "grasses /grasslike" under General Appearance. When we tried this, we got 279 suggestions for native grasses. You can narrow this down by also selecting on Light Requirements and Soil Moisture. If you decide you want to add some wildflowers to your meadow, go to Recommended Species, select South Carolina on the map, and "herb" (herbaceous blooming plant) under General Appearance. We got 40 possibilities; again, this list can be refined by choosing Light Requirements, Soil Moisture, Duration, etc. We are going to suggest four of each just to get your started. Follow each link to the page on that individual plant to find out expected size, propagation methods, benefits, and so forth. 

Grasses for a meadow in South Carolina:

Bothriochloa laguroides ssp. torreyana (silver beardgrass)

Chasmanthium latifolium (Inland sea oats)

Elymus villosus (hairy wildrye)

Muhlenbergia capillaris (hairawn muhly)

Herbaceous blooming plants for a meadow in South Carolina:

Asclepias tuberosa (butterfly milkweed)

Conoclinium coelestinum (blue mistflower)

Coreopsis lanceolata (lanceleaf tickseed)

Echinacea purpurea (eastern purple coneflower)

From our Native Plant Image Gallery:

Bothriochloa laguroides ssp. torreyana

Chasmanthium latifolium

Elymus villosus

Muhlenbergia capillaris

Asclepias tuberosa

Conoclinium coelestinum

Coreopsis lanceolata

Echinacea purpurea