CHARLESTON, S.C. -- A rain storm followed by gloomy skies does not sound like ideal weather in which to visit the nation's oldest public garden. But in the end, the Pittsburgh-type weather gave me a special appreciation for Magnolia Plantation and Gardens, which opened to the masses in 1872.

Magnolia was begun in 1676 by the Drayton family and is probably best known for its vast collections of ancient camellias and azaleas. As far back as the late 1800s, its nearly 500 acres on the banks of the Ashley River was a popular travel destination, drawing flower-loving tourists from as far away as Europe. And just four miles down the road is Middleton Place, another longtime tourist magnet that just happens to be America's oldest landscaped gardens.

Like the thousands of sightseers before me, I looked forward to strolling the formal allees and romantic, billowing beds of these century-old landscapes. But what I really wanted was to get up close and personal with low-country wildlife in the Audubon Swamp Garden at Magnolia. I quickly discovered that swamps, which are kind of unearthly to begin with, grow even more beautifully eerie when it's foggy and overcast -- a perfect setting for the alligators I so desperately wanted to see!

It turns out that gators only crawl out of the water when there's sun to bask in. But no matter. There were plenty of other things to see as I wandered across the wide wooden boardwalk and bridges that zigzag the garden's 60 acres of blackwater cypress and tupelo swamp. Each spring, hundreds of long-legged herons, egrets and other waterfowl nest within a few feet of the walking path; several clusterings of trees were so thick with egrets that it appeared their limbs were stuffed with cotton.

The swamp is also home to turtles, river otters, ducks and more than 200 species of birds. It's easy to see why famed artist and garden namesake John James Audubon came here to observe waterfowl in the 1800s. And its steamy, swampy scenery was the site of Wes Craven's horror flick "Swamp Thing" in 1982.

Azalea, wisteria and Cherokee rose, a climbing evergreen vine with waxy white blossoms, offer the occasional punch of color. But mostly, the swamp garden is a study in green, brown and gray -- from the floating gobs of pea-soup "scum" on top of the water (actually duckweed) to the half-submerged logs, to the spiky needle palms along its banks, to the floating islands of wax myrtle, buttonbush and dollar weed amid the tupelo and cypress trees. And everything, it seemed, was heavily draped in festoons of silvery Spanish moss.

Other sites near the water include a row of antebellum slave cabins that were occupied from their construction in 1825 through the 1930s and a rare African-American plantation graveyard. It took about an hour to wind my way through this diverse habitat. Then, with rain once again threatening, it was on to a quick tour of the plantation's other gardens.

Originally designed as a formal garden, Magnolia embraced the "new" style of English informality during the Industrial Revolution. In the 1820s, John Grimke Drayton planted the first Camellia japonica, and by 1845, Magnolia counted more than 100 varieties. It is now the "signature" plant of Southern gardens. He later added Azalea indica, creating one of this country's most beautiful collections of this spring-flowering shrub.

I wandered first through the Biblical Garden, which contains flowers and plants named in the Old Testament. I also tested my navigational skills in The Maze, which replicates the famous hedge maze at Hampton Court in England. Created from more than 500 Camellia sasanqua plants interspersed with Burford holly, it includes nearly a quarter-mile of intricate pathways. Then it was on to the main attraction: the vast Camellia Collection.

Most of the 900 or so cultivars now growing in Magnolia's gardens had peaked in February, as evidenced by the lush piles of red and pink flowers on the ground. (In South Carolina, camellias flower November through March.) But the evergreen shrubs -- some of which were 12 feet or more and laden with flowers 5 inches in diameter -- were amazing nevertheless; during the plantation's camellia festival that begins in mid-January, I imagine it would take several hours to see it all. Besides, thousands of azaleas along the gravel and dirt paths had just started to bloom, along with daffodils, dogwood and humongous clusters of intoxicatingly fragrant wisteria.

Azalea and a few still-blooming camellias were in colorful supply at the second historic plantation I visited: Middleton Place.

In 1741, Henry Middleton -- who in 1774 became president of the First Continental Congress -- acquired the property and began laying out the 65-acre garden that reflected the grand classic style so popular in Europe. Included in his bold and expansive plan were long and narrow allees planted with trees and shrubs that were trimmed to appear as green walls. The site also has ornamental ponds shaded by a variety of trees, and garden "rooms" laid out with precise symmetry and balance.

The original plantation house sat high on a hill above the Ashley River, and Middleton wanted any visitors who arrived by boat to be suitably impressed. So his design includes a giant parterre bordered by 155-foot-long flower beds that lead to a series of rolling terraces overlooking the river. As docent Ritha Tuten explained during a free hour-long introductory tour of the grounds, it took 100 slaves almost 10 years to complete the work.

Middleton Place was burned and looted by Union troops in 1865, then suffered more damage during the great Charleston earthquake of 1886. The tremors were so severe that they ripped open the terraces and sucked the water out of the ornamental lakes. But while heirs were able to hold on to the family plantation, the gardens lay overgrown and neglected until inherited by J.J. Pringle Smith in 1916. He undertook the huge project of restoring the gardens to their original 18th-century splendor and opened them to the public in the 1930s.

There's almost too much to see at Middleton Place, especially if you're short on time. So with Ms. Tuten's guidance, I had to settle for the highlights: a pair of "secret" gardens in which children would have played, an octagonal sunken garden once used as a bowling green, and a wheel-shaped sundial garden filled with China and tea roses first propagated in the 18th century.

On a corner near the azalea pool, I admired the marble "Wood Nymph" statue created by Rudolf Schadow in 1810. To protect it, family members buried it along with their silver during the Civil War. I also marveled at the landmark Middleton Oak, which stands 85 feet tall and has a limb spread of 145 feet. Draped in Spanish moss, this 800-year-old live oak served as an Indian trail marker long before Columbus discovered America.

We also got to see a rice mill and demonstration rice field. Rice was grown in flooded rice fields adjacent to the river until the emancipation of slaves after the Civil War.

The real thrill, however, was seeing the hillside above the Rice Mill Pond. It was planted in the 1920s and '30s with 35,000 azaleas, most of which were in full bloom on the sunny April day I visited. Knowing that in a few short hours I'd be back in Pittsburgh, where even crocus had yet to push through the ground, I drank in all that glorious color.