Longwood Gardens

Longwood's Main Fountain Garden. (In 1906 Pierre S. Du Pont purchased the land to save its collection of historic trees. Preservation efforts have expanded making it "one of the world's great horticultural showplaces. (JED KIRSCHBAUM, Baltimore Sun / April 28, 2011)

Online refer: For more garden photos, go to baltimoresun.com/travel. For more information on gardening, read Susan Reimer's blog at baltimoresun.com/gardenvariety

When Cheval Opp retired from IBM, she knew exactly what she would do with her time.

Visit gardens.

"My whole life at IBM, whenever they would send me anywhere, I would take an extra day or a weekend and visit gardens," she said. "When I realized I'd be retiring and I could do anything I wanted, I knew what it would be."

Now Opp helps travelers and day trippers arrange tours of the many public gardens in the Mid-Atlantic area. She helps choose which gardens to see and how to time the visits.

"This is my second act," said the woman who calls her garden tour company (of course) Cheval's Second Act.

National Public Gardens Day is Friday, when America celebrates the role of these public gardens in promoting environmental concerns. But public gardens have an impact on visitors that goes beyond plant or water conservation and reaches into the spirit.

"Studies show us that even the plant on the window sill is calming," said Opp, who lives in Dunn Loring, Va., and also writes and lectures about public gardens.

"We know that these things are alive, and we are part of their life cycle. And we know if they are alive, we are alive," she said.

The Mid-Atlantic has an abundance of stunning public gardens not only because of the industrial wealth that was once centered in this part of the East Coast but because the climate is moderate enough to support a vast range of plant life.

Choosing the best of them to visit isn't easy. There are dozens in Pennsylvania, Delaware, Maryland, Virginia and the District of Columbia that are worth a day trip.

Opp's advice?

If you want to see a garden that is beautiful every season of the year, go to Dumbarton Oaks in Washington.

"It is a work of art," she says.

Here's a sampling of other gardens in the region — from huge landscapes to little green gems — that are worthy of a springtime stroll.

Nemours

Nemours Mansion and Gardens, the 300-acre estate of Alfred I. du Pont, is named after the du Pont ancestral home in France. The mansion is an excellent example of a modified Louis XVI French chateau. The gardens, their design influenced by du Pont's many trips to Europe, are the largest example of French formal gardens in North America, patterned after the gardens of Versailles.

What's blooming: the Reflecting Pool, one acre in size with 157 jets, backed by Japanese cryptomeria, pink flowering horse chestnut, and pin oaks.

Don't miss: The Sunken Gardens, featuring a large lake and grottoes and the Temple of Love with life-size statue of the goddess Diana.