Plants adapt through generations where they are planted. Some of their adaptations become apparent after watching the plants grow. But unless plants for sale are grouped as annuals or perennials in the greenhouse, it’s hard to tell them apart just by their appearance.
Zinnias tolerate hot sunny days but not frosty Fall evenings. The annual zinnia completes its life cycle in a growing season from seed to starter plant to flower to seeds.
Perennials live and grow longer than two years. Robust rudbeckia perennials have variability in lifespan within the species grown in the same conditions in the same flowerbed!
Rudbeckia hirta ‘Indian Summer’ flowers peaked in summer their first year, and late bloomers still appear at this time.
Rudbeckia hirta ‘Green Eyes’ was much slower to develop this year. Starter plants were set out in early June, after a cool spring, and are now in first-year bloom. Growing such plants year after year reveals some of their adaptations that fit the regional environmental conditions.
Gardening in widely different regions shows us that some plants are perennials in some locations and annuals in others. And we haven’t mentioned biennials that bloom in the second year. More to find out.
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Plant Exchange Blog 
Annual bedding plants are not my favorite, for a few reasons, but partly because most have potential to grow as perennials, but do not get the chance.