When Janet Leopold moved to Kauai from Los Angeles in 1988, she knew it was also time to make a big career change. She had worked in the corporate world for 16 years; in her new island home, she wanted to do something she was passionate about.

"Protecting the environment was high on my list, but when I joined the National Tropical Botanical Garden, I had no idea about the depth of its work," said Leopold, the organization’s director of communications. "Our botanists and conservationists took the time to teach me how thin the line is between rare and extinct."

At the time, propagators in NTBG’s nursery used little red plastic stakes to identify pots containing endangered plants. "I’ll never forget walking in there for the first time, seeing a sea of red and thinking that each of those plants was wearing a little red badge of courage," Leopold said. "That showed me how fragile Hawaii’s native plants are, and how much they need our help."

The mission of the nonprofit National Tropical Botanical Garden (www.ntbg.org) is to "enrich life through discovery, scientific research, conservation and education by perpetuating the survival of plants, ecosystems and cultural knowledge of tropical regions." NTBG owns one garden in Florida and five preserves and three gardens in Hawaii, including 200-acre Mc­Bryde Garden in Lawai Valley on Kauai. It manages 80-acre Allerton Garden, which adjoins Mc­Bryde Garden, under an agreement with the Allerton Gardens Trust.

Trails, a fishpond, stone walls, agricultural terraces and other archaeological sites suggest Lawai was an important Hawaiian settlement in ancient times. Trams transport visitors to the valley floor on an old sugar cane railroad bed that borders secluded Lawai Bay and cliffs cloaked with purple bougainvillea — a favorite of Queen Emma, who once owned this land.

The queen sold the property in 1886 to Judge Duncan Mc­Bryde, who wanted to cultivate sugar there. Mc­Bryde Sugar Co. operated from 1896 to 1960. Four years later the Pacific Tropical Botanical Garden (renamed the National Tropical Botanical Garden in 1988) was established by congressional charter.

In 1970 the organization’s founding trustees purchased 171 acres in "upper" Lawai Valley from the Mc­Bryde family for its first garden, which was named Lawai Garden. Expanded over the years as funds were obtained to buy adjacent parcels, that garden now bears the Mc­Bryde name. It harbors the largest collection of native Hawaiian plants in existence, many of which are threatened, endangered and even extinct in the wild.

Visitors to McBryde Garden can see 23 of the 26 species of the native Hawaiian loulu palm, including Pritchardia limahuliensis, which is found only on Kauai. They can also admire the 27 "canoe plants" that Polynesian voyagers brought to the islands to use for food, clothing, shelter, tools, medicine and more. Among these are plants that have become synonymous with Hawaii: taro, ti, coconut and sugar cane.

In 1938 Robert Allerton, a wealthy Chicago native who was an avid collector and patron of the arts, acquired about 65 acres of the seaside "lower" section of Lawai Valley from the Mc­Brydes (he subsequently purchased about 15 additional acres). There he and his adopted son, architect John Gregg, built a house and created gardens largely composed of exotic plants that had caught their eye during their travels in Southeast Asia and the Pacific.

Sharp-eyed movie buffs will recognize the enormous Moreton Bay fig trees that appeared in the 1993 blockbuster "Jurassic Park" (the trees’ buttress roots alone can stand 8 feet high. Also of note in Allerton Garden are the skunk tree, known for the musty odor emitted by its pretty, rust-colored flowers; the angel’s trumpet tree, whose fragrant blossoms belie the fact that they contain toxic alkaloids that can cause dizziness, hallucinations, blurry vision and, in large doses, death; and the talipot palm, which at maturity (generally 30 to 50 years) produces a single inflorescence containing up to a million flowers and measuring up to 16 feet long — the largest of any plant.

Serene areas are adorned with statues, pools, fountains and miniature waterfalls. They are magnificent tributes to the artistry of nature and man.

While its gardens have been hailed for their beauty, research and conservation remain the core of NTBG’s work. "Our scientists’ extraordinary efforts to protect rare native Hawaiian plants have been documented by, among others, National Public Radio and National Geographic," Leopold said. "Dramatic photos have been published of our field botanists dangling on ropes along sheer 3,000-foot cliffs to gather seeds from plants that would otherwise have gone extinct."

Her face lights up whenever she talks about NTBG’s "poster child": alula (Brighamia insignis), a member of the bellflower family found only on Kauai and Niihau. When last seen in the wild in 2006, it was down to one plant on the Na Pali Coast. Today, 575 alula plants are thriving in NTBG’s gardens, 360 of them at Mc­Bryde Garden.

"Propagation of alula has been one of our great successes, but there’s so much more work to do," Leopold said. "When visitors see rare Hawaiian plants up close in our gardens, I hope they realize what a special opportunity that is. In my job, when I share stories about these precious plants, I hope I’m getting the point across that saving even one of them from extinction is a huge accomplishment not only for NTBG, but for the planet."

Cheryl Chee Tsutsumi is a Honolulu-based freelance writer whose travel features for the Star-Advertiser have won several Society of American Travel Writers awards.