A. "Perennials are flowering plants that come back year after year, but some come back year after year much longer than others," said Eileen Nelson, an herbaceous plant specialist with UW-Madison and UW-Extension.

While petunias, marigolds and other annuals grow from seeds, produce flowers and seeds, and then die in one growing season, perennials grow back each spring from their roots or underground bulbs. And the so-called long-lived perennials, including peonies, hostas and irises, can do this for up to 15 or 20 years, said Nelson.

On the other hand, perennials such as columbine and delphinium naturally peter out — or as botanists say, "lose their vigor" — in just a few seasons. But Nelson said there's a lot you can do to make them last as long as possible, including planting them under the right sun conditions and cutting them back each fall.

You can also coax plants such as daffodils into returning by snapping off the seed heads, which are left behind after the flower petals fall. Doing so causes plants to divert the energy they generate through photosynthesis toward enlarging their bulbs — rather than making seeds — ensuring they'll have ample reserves to grow again the following year.

"What you're doing is suggesting to the plant that it put its energy someplace else," said Nelson. "I think that's one of the fascinating things about plants: You can manipulate them to some degree."

— Produced in cooperation with University Communications

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