Plants and flowers fall into one of two categories: perennials or annuals. Perennial plants will bloom, die back, go dormant and return to your garden the next growing season. Annual plants flower, produce seeds and die; they do not return to the garden of their own accord.
Perennials - Pros
Perennials require little maintenance and will reward you with blooms year after year; they also multiply, providing you with additional plants over the years for free. Purchase a perennial this year and you will not need to buy new plants.
Perennials - Cons
Since perennials multiply, they will require periodic thinning. If you do not thin the plants, overcrowding will occur and flower production will decrease. Thinning requires digging up some of the plants, pulling or cutting them apart and replanting; this process must be repeated about once every three years.
Annuals - Pros
Annuals are available in a wide variety of sizes and colors and only last a year, so each year you can pick new and different plants; annuals are also great fill-in plants while you wait for perennials to multiply.
Annuals - Cons
You must purchase and plant a new crop of annuals each year.
Benefits of Using Both Perennials and Annuals
Most gardeners prefer a mix; perennials provide constant beauty, while the annuals give the gardener the opportunity to change things up a bit.