Divide most Midwestern native plants---it is a sure way of reproducing plants identical to the parent and is one of the easiest. Use a garden fork to pry apart clumps of grasses like Bluestem or Switch grass. Lift and gently pry apart "crowns" of flowers like pale spiked lobelia, black-eyed Susan and purple coneflowers. A crown has its own set of roots and one or more buds from which plants grow above ground. Divide spring-flowering plants in fall and summer-flowering plants in spring or fall. To find crowns, shake as much dirt off as possible and swish the clump in a bucket of lukewarm water to remove all of the dirt. Plants with large crowns like wild bergamot (beebalm) may fall apart easily with little need to remove dirt. Divide plants in the morning when they are rested and moist and don't let their roots dry out.
Collect seeds from your or a neighbor's plants. Prairie grasses reproduce readily by seed and flower seeds generally ripen in the fall. Blazing star produces tall spikes of seed that should be planted in fall but some flowers, like cranesbill or Western sunflower, should be planted in spring. Jack-in-the-pulpit must be grown from seed sown in late fall. Collecting seeds from existing plants presents two problems. One is collecting seed at the right time. Midwestern plants are successful if they release their seeds at the right time and tend to do it quickly; the gardener must be ready to snatch ripe seeds before they are propelled outward. They must then clean and store the seeds in a cool, moist environment, stratify, scarify and plant them when appropriate. Even after that, collected seeds are more likely to produce a plant that differs from its parent; insects are indiscriminate about the varieties that they cross-pollinate. Seeds bought from reliable wildflower sources will always grow true.
Use stem cuttings to produce offspring that are identical. Cut non-flowering stems of branched plants like rudbeckia or smooth blue aster. Take stem cuttings of prairie cinquefoil in fall. Prairie and sand coreopsis can be propagated by stem cuttings taken in summer. Cut stems long enough to pinch off the tips, leave about four leaves and remove leaves from the bottom inch and a half of stem. Root them in a sterile medium of peat moss and perlite placed in a greenhouse made with a plastic bag.
Make root cuttings from plants like purple coneflowers that create thick masses of fibrous roots. Lay 2- to 3-inch-long cuttings lengthwise in a box of sand and cover them lightly. Mist the sand to keep roots and seedlings moist and transfer little plants to pots or the garden when they are a few inches tall. Conserve moisture with a plastic bag greenhouse.