Answer: Most people cannot tell whether a plant is an annual or a perennial just by looking at them. That's because what might be a long lived perennial in a warm winter climate such as southern California, might live only a season in a cold winter climate such as yours. The best way to tell is to look at the labels attached to the plants.
In general, annuals grow for a single season. They grow, flower, set seeds and die. Perennials grow for three or more years and while they may die down in the winter, the roots will produce new stems and foliage every spring.
The best advice is to look at the label or find the name in a gardening book or even online. This will tell you whether a plant can be expected to live 3 or more years in your garden.
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