The U.S. Botanic Garden is once again growing roots at the base of the Capitol grounds.

Since the garden reopened in December 2001 after a $33.5 million, four-year renovation, its collections have continued to mature and thrive in their improved surroundings. The conservatory first opened in 1933 but fell into disrepair, forcing a portion of it to be torn down in 1992. After Congress passed legislation approving the renovations and appropriated the funds, renovations began in 1997.

Now at the landmark conservatory, vines are literally climbing up the glass walls and flowerbeds are expanding into their surroundings.

Ground cover is spreading across displays to neighboring plants, a positive sign of the plants’ health, said Holly Shimizu, the garden’s executive director, but gardeners must cut it back as part of routine maintenance.

“We like to let them grow, but we can’t let them take over,” she said.

And as the plants continue to grow, so does the number of visitors who take advantage of the increasing activity at the east end of the National Mall.

The number of daily visitors ranges from 2,000 to 4,000, including horticulturalists, government officials and tourists from around the globe, Shimizu estimated.

She and the 52 other gardeners work to create plush, ever-changing displays from the 20,000 types of plants the garden has in its collection between the conservatory and the production facility in Anacostia. They also work to make sure there are visible signs for each plant on display with just the right amount of information.

For Shimizu, transitioning through the Botanic Garden’s reopening has meant being increasingly busy with more visitors, additional collaboration with other horticulturalists and more work to coordinate garden display within the staff.

One afternoon last month, several of her co-workers jokingly asked her if she knew where she was when she returned to her office in the back corner of Bartholdi Park.

The co-workers thought she had gotten lost in the gardens, they said, as she returned from almost three hours of giving guided tours to different guests.

“If you have someone explain to you it takes on a whole new meaning,” Shimizu said, adding that the garden has expanded docent services and offers more educational public programs.

But housing such a wide variety of plants is what Shimizu considers the greatest success of the renovation. The conservatory is able to house almost any plant in the world due to a highly specialized staff and the building’s unique features, she said.

The conservatory’s temperature and atmosphere are constantly analyzed by a computer that can automatically adjust temperatures, humidity and wind flow.

In a room at the back of the conservatory, John Gallagher, the operations manager, monitors computer screens with environmental information.

“The building is really too complex to do all of this manually,” he said, adding that they still have to be prepared in case of mechanical problems.

While the machines keep the gardening staff from having to constantly check whether plants need watering, they stay busy planning exhibits, rotating displays and figuring out what gets the most visitor response. Shimizu says the goal is to be “museum quality.”

Shimizu works to create partnerships with other groups such as the Smithsonian Institution, which has begun sharing plants from its botany collections. She also helps organize special events such as the garden’s summer highlight — the blooming of the titan arum, the world’s largest flower. The rare blooming of what is also called the corpse flower brought national attention to the garden and many information requests to Shimizu. For the former director of public programs for the Botanic Garden, the spotlight was no problem during what she called a very exciting few days.

Before becoming director of the gardens, Shimizu had been the managing director of the Lewis Ginter Botanical Garden in Richmond, Va., and had hosted a television show called “Victory Garden.” She has also worked at the Royal Horticultural Society in Surrey, England, and at the national herb garden at the National Arboretum.

Botanic Garden employees work to maintain plants with particular significance to historic, cultural, medicinal or economic developments, as well as plants that are rare or endangered. Heirloom plants that have not been hybridized will be on display through October. Another exhibit displays plants that have been used to treat illnesses including ovarian cancer and HIV and others that are used in diet pills.

Shimizu emphasized that while the gardens can be very educational, they still want visits to be a calming experience. She encourages visitors to relax in the gardens and take time to rest on the benches or bring lunch and eat in Bartholdi Park.

“Gardens play an extremely important role for human renewal,” she says. “But being a pretty garden is only a part of what we are.”