Aster can be easily identified because it looks like little daisies. Generally, it's an excellent perennial to know about for a lot of reasons: it look great in a border, can be mixed with many different perennials, can tolerate full to partial sun, and has a wild yet clean appearance that can appeal to all design sensibilities. It's also a late bloomer, showing it's colors in late summer to early fall when others are going dormant.
The one featured here at the Shelter Island Retreat is actually Peony Dutchess, which has button like flowers and looks great planted en masse. This link is for a company that sells them in bulk as seeds.
Size: can grow 10"-6' depending on variety
Sun: Full to partial
Water: likes moist, well -drained soil