Perennials and annuals are different types of plants.  Perennials live for more than two years, outliving their annual cousins. The rootstock - the root system that sustains a perennials life - is essential for surviving cold winters and harsh conditions for these plants. And some plants are known to survive for ten consecutive years or more! This lifestyle allows perennials to set root in the ground, making them excellent candidates for landscapes demanding erosion protection.  For this reason, perennials are also superb weed blockers and reducers.  A well maintained perennial garden will become easier and easier for weed pulling as your perennial plants grow and stretch out their roots - beating out the competition.