This mint is an easy growing herb. It can spread as far as you allow it to. Peppermint boasts pale purple flowers in summer, while its pointed, serrated leaves are a dark green with red tinges. As far as propagation is concerned, the seed on the market is inferior. It doesn't always run true to species.
Root cuttings are a better way to propagate.
Plant root cuttings in potting soil, water them, and leave. Garden-grown peppermint should be divided about every three years or root runners will show up everywhere. Mint rust can appear as little rusty spots on leaves. Remove the leaves immediately because rust will wash off into the soil and spread to other plants. Try burning the affected patch.