NEW YORK - It's lovely to visit a garden on a spring day, surrendering to the scents, colors, and even the sounds, of birds chirping or the breeze rustling a dogwood tree heavy with blossoms.

But there's also something to be said for taking a close look, guided by an expert who can reveal a garden's secrets and point out the wonders that a casual stroll might miss.

Many botanical gardens offer guided tours, from a docent-led walk to see seasonal highlights, to ticketed tours focusing on some aspect of the garden's collection. This spring, the Brooklyn Botanic Garden is introducing several types of guided tours for groups of 20 or more.

"It's a way to really get in contact with the plants," said Mark Fisher, a curator at the Brooklyn Botanic Garden.

Walking through the garden's Steinhardt Conservatory greenhouse with Fisher on the "Meet the Curator" tour, you see things that you'd miss on your own. He points out papayas clustered in a treetop; the architecture and artistry of a bonsai's pruned branches, and an orchid growing on a tree, its roots seemingly suspended in the air.

"See the vellum?" Fisher said, pointing to the soft, sticky, tiny hairs on the orchid's roots as it hung from a tree branch. "They get their nutrients by attracting leaf litter." This type of plant is called epiphytic, as opposed to terrestrial, Fisher noted.

Brooklyn Botanic Garden spokeswoman Leeann Lavin said there's an increased interest in these types of tours thanks to "baby boomers who want to keep learning" and other visitors who are looking for a "more intimate experience" than just taking a walk on a nice day.

For those who avoid big cities, the Cheyenne Botanic Garden offers glimpse of how and what to grow in the Rocky Mountains. Director Shane Smith said the Cheyenne gardens receive over 42,000 visitors each year from all 50 states and over 27 countries.

Smith's facility offers a solar-powered conservatory and nine acres of landscaped gardens.

And it turns out some travelers prefer the small-town atmosphere.

"People tell us that visiting the Cheyenne Botanic Garden is a different experience than a big city public garden," Smith said. "We hear words like, 'It is more intimate.' 'It feels more accessible, I'm not afraid to touch a leaf or smell a plant.' 'I love talking to the volunteers - they are so knowledgeable.' and 'I can't believe this place is free!'

Smith's operation doesn't have the budget to offer drop-in tours, but visitors are always welcome.

"We do offer a grounds map and our grounds are open to the public from dawn to dusk," Smith said. "… Our web site (www.botanic.org) is also helpful in planning a tour of our grounds and includes information about specific gardens, events and driving directions."

Historic homes often have noteworthy gardens, too. No visit to Monticello, Thomas Jefferson's estate in Virginia, would be complete without a tour of the gardens. Jefferson grew hundreds of varieties of vegetables and fruits, and he filled his flower beds with a mix of European plants, like tulips, and native American specimens, including some collected by Lewis and Clark on their journey west. But part of the charm of the tour is learning that some of Jefferson's gardening experiments - including a vineyard and a dream of producing syrup from maple trees - failed.

Some locales organize tours of private gardens every spring, giving visitors a peek inside historic and often well-appointed homes that are not otherwise open to the public. Newport, R.I., hosts a "Secret Garden Tour," June 15-17. Natchez, Miss., has a "Symphony of Gardens Tour" May 4-5. Atlanta's Gardens for Connoisseurs Tour, May 12-13, is a fundraiser for the Atlanta Botanical Garden. Historic Garden Week in Virginia, April 21-28, sponsored by the Garden Club of Virginia, features 30 tours around the state, from 18th century James River plantations to walled urban retreats.

Most visitors to botanical gardens are day-trippers, but you can also plan a vacation around far-flung gardens. Elderhostel, a tour company that specializes in educational travel for older adults - http://www.elderhostel.org or (800) 454-5768 - offers trips to gardens in destinations ranging from Southern cities and the West Coast to England and New Zealand.

Adam Hurtubise, Elderhostel spokesman, says the number of garden programs offered by the company, along with enrollment, is on the rise. Also popular, he says, are Elderhostel programs with a service component, where participants can get their hands dirty and work on historic gardens in addition to taking a tour. One such Elderhostel program includes an option to work on the Victorian garden at the Emlen Physick Estate in Cape May, N.J.

Here are a few garden tours from around the country. Call ahead for reservations, fees and visiting hours, which often change with the seasons. Ask about customized group tours, which are available at many botanical gardens.

Garden and estate tours

*Atlanta Botanical Garden: http://www.atlantabotanicalgarden.org or (404) 876-5859. Docents lead tours each Tuesday afternoon (free with admission). Private group tours can be arranged.

*Bloedel Reserve: Bainbridge Island, Wash., http://www.bloedelreserve.org or (206) 842-7631. Reservations required to visit the reserve. Free group tours for six or more; call well in advance.

*Brooklyn Botanic Garden: Brooklyn, N.Y.; http://www.bbg.org or (718) 623-7200. Guided tours (free with admission) offered weekends, 1 p.m.; no reservations needed. Group tour offerings (718) 623-7220, for 20 people or more) include garden seasonal highlights with buffet lunch, $32 a person; Palm House luncheon tour, $53-$63; "Meet the Curator" tour, $40 (with lunch $60); art and garden tour, $45.

*Cheyenne Botanic Gardens: Cheyenne; http:www.botanic.org or (307) 637-6458. Open to the public dawn to dusk for self-tours. Solar conservatory is open 8 a.m.- 4:30 p.m. Monday-Friday and 11 a.m.-3:30 p.m. on weekends and some holidays. No admission charge, although donations are gratefully accepted.

*Chicago Botanic Garden: Glencoe, Ill.; http://www.chicagobotanic.org/tours or (847) 835-5440. Earth Day Walk in search of wildflowers, April 28; Heritage and Lakeside Gardens tours, May 5; tree care tours, May 12 and 19. Spring Garden Walks, Saturdays, 1 p.m., April 28-May 26, free. Ticketed tours, $4-$32, include tram tours (starting in April), walking tours, group tours, behind-the-scenes tours of greenhouses and laboratories, a "Bright Encounters Tour" by tram (Heritage, Rose and English Walled Gardens), twilight tours on summer evenings. Boxed lunch option on some tours.

*Denver Botanic Gardens: http://www.botanicgardens.org or (720) 865-3533. Drop-in tours, 11 a.m. and 1 p.m., Saturdays and Sundays; themes include general highlights, water gardens, trees and other subjects.

*Desert Botanical Garden: Phoenix, Ariz.; http://www.dbg.org or (480) 941-1225. Daily public tours, "Taste of the Desert" tours, nighttime "Summer Flashlight" tours (free with admission). Beginning March 1, bird watching and spring wildflower tours.

*Garden in the Woods: Framingham, Mass., http://www.newfs.org or (508) 877-7630. Open April 14-Oct. 31. New England Wild Flower Society offers tours ($10 per person) of seasonal highlights, cart tours for visitors needing mobility assistance.

*Huntington Botanical Gardens: San Marino, Calif.; http://www.huntington.org or (626) 405-2240 (for tours). Informal, walk-in tours available with admission. Tours requiring reservations include estate tours, $17; and "Tea & Tour," $49 (groups of four or more).

*Middleton Place: Charleston, S.C., http://www.middletonplace.org/ or (843) 556-6020. "Camellia Walks" tours (free with admission) focusing on camellias; 11 a.m., March 1, 3, 6, 8, 10, 13, 15, 17, 20, 22, 24; reservations required.

*Missouri Botanical Garden: St. Louis, Mo.; http://www.mobot.org or (800) 642-8842. Guided walking tours (free with admission) offered daily at 1 p.m. Reservations required for tours of the park's Woodland Garden, Ottoman Garden, George Washington Carver Garden and more; fees vary.

*Monticello: Charlottesville, Va.; http://www.monticello.org or (434) 984-9822. Guided tours of Thomas Jefferson's restored flower and vegetable gardens, tree grove and fruit orchards offered eight times daily April 1-Oct. 31 (free with admission).

*San Francisco Botanical Garden at Strybing Arboretum: http://www.sfbotanicalgarden.org or (415) 661-1316. Daily docent-led tours, family walks and birding walks (free with admission).