Limahuli valley: Hawaii's ancients replanted Limahuli Gardens. FRESH water is a commodity that all cultures need for prosperity. Kaua'i, the most northern and oldest of the volcanic islands of the Hawaiian archipelago, enjoys water in abundance. Justly dubbed The Garden Isle, Kaua'i is a 1456sq km jewel of rich volcanic soil and high rainfall in which tropical plants - both native and exotic - flourish. The island, discovered by Polynesian voyagers centuries ago, is blessed with spring-fed waterfalls that crash on to white-sand beaches, while jungle-covered, emerald green mountains melt into the sea and groves of palms bend and sway under a bloated moon. Archaeologists believe the earliest settlers to the Hawaiian Islands had arrived by AD200, probably from the Marquesas Islands to the south. A second wave of immigrants arrived in about AD1200 from the islands around Tahiti, bringing with them a complex social and religious system. The Limahuli valley, with its protective mountain folds, its springs and streams, heavy rainfall, and its rich, abundant marine life soil, was among the first areas settled. On the beautiful, rugged north shore, Limahuli Garden and Preserve is set in a 500ha canyon in the shadow of mountains dominated by the twin peaks of Hihimanu mountain. Fed by a pristine stream that crashes from the mountain summit, Limahuli, just past the unspoiled village at Hanalei Bay and the famous Tunnels surf beach, is home to the world's largest collection of rare and endangered tropical plants, many brought by the first Polynesian settlers. After restoration of the site's ecosystem, there are native fan palms, the endangered bell flower (Brighamia insignis), rare hibiscus, taro (Colocasia esculenta), breadfruit and other indigenous food plants. A $US21million Botanical Research Centre was completed there in 2008. On the footprint of the ancient Hawaiian civilisation, the garden follows traditional systems of cultivation that once provided everything needed for a growing population. The Canoe Garden showcases the culinary, medicinal and decorative plants that the earliest settlers brought in their canoes, along with pigs, dogs and poultry. The garden has been re-created to demonstrate the practices still employed in much of Hawaii today. There is taro (Colocasia esculenta), a staple food, and again thriving in terraces enveloped by lava rock walls 700 years old. Every part of the taro is edible when cooked correctly: the underground roots are the best known and are roasted to resemble a sweet potato. The cordyline (Cordyline fruticosa), known locally as ti, earned its place in the earliest canoes that crossed the Pacific because of its many uses. The leaves are used for wrapping and cooking food, often in pits in the ground, for making clothes and bedding, as is the paper mulberry (Broussonetia papyrifera). Turmeric, which dates to pre-history, (and featured in King Nebuchadnezzar's Hanging Gardens of Babylon, located in modern-day Iraq), is a member of the ginger family. It was also brought to the islands by the early Polynesians and was valued not only in cooking but in treating ailments. More than 70 varieties of banana (Musa spp.) were developed by early Polynesian settlers; a few are maintained at Limuhali, valued for their nutritional qualities as well as for wrapping food and for roofing. The versatile coconut palm (Cocos nucifera) was one of the most important species brought by the first canoeists, providing food, drink, roof thatching, hut matting, rope, brooms and canoes. Oil extracted from coconut meat provides hair conditioner and skin lotion. Coconut milk contains calcium, phosphorus and protein. Reaching up to 30m, the coconut palm has long provided essential shade. And it may be local folklore, but it is said that building regulations restrict buildings to the height of the tallest palm tree. Changes to the cultural and ethnic makeup of Hawaii came with the arrival of James Cook in 1778. And during the 18th and 19th centuries a developing sugar and pineapple industry attracted immigrants from China, Japan, Portugal and The Philippines. Many brought their own favourite plants with them, which were integrated into the botanical language of Hawaii, which became a US protectorate in 1894 and a US state in 1959. These included frangipani (Plumeria spp.), mangoes and the silk flower (Albizia julibrissin), which have made themselves at home, in places covering hillsides and choking out the native forests. These are islands landscaped with the hibiscus that contributes so much to the spirit of Hawaiian culture, with the highly scented evergreen frangipani (Plumeria obtusa) and with palms that bend in response to decades of gentle breezes. It is particularly poignant, then, to learn that Hawaii has more plants facing extinction than any other region in the world - but the island does, indeed, continue to enjoy the feel of an unspoiled tropical paradise. Happy Christmas, and happy gardening everyone. Holly Kerr Forsyth attained a PhD on 19th and 20th-century pastoral gardens.