Quilted among the Big Island’s landscapes of verdant rainforest and barren volcanic rock, the ancient fields of leeward Kohala stretch as far as the eye can see. Walking with a GPS, Professor Michael D. Graves explores a wide meadow that’s used as farmland during the summer months. From the ground, it looks like any other field. But viewed from above, one can see the faint parallel lines running for hundreds of feet in the grass—the buried remains of massive terraces. Dr. Graves, a former University of Hawai‘i at Manoa researcher (now at the University of New Mexico) has devoted the past ten years to studying the sweet potato, an herbaceous creeping vine in the morning glory family that was once cultivated in these fields. The sweet potato’s tale is a complex story that weaves history, geography, agriculture and genealogy. Most of all, it contributes to our evolving understanding of Hawai‘i’s importance as a cultural crossroads, deepening our appreciation for the early Polynesians’ achievements in trans-oceanic voyaging.
The first Polynesians inhabited the lush windward sides of select Pacific islands roughly between AD 1 and 600; they expanded into dryer leeward areas in later centuries. By the time of his arrival in 1778, British explorer Captain James Cook observed that the sweet potato was already an essential crop for Hawaiians.
The sweet potato Cook saw arrived in Hawai‘i at least a few centuries earlier than the Okinawan purples we know and love today. (Europeans introduced those to Asia in the 1500s, and they later came to Hawai‘i from the Far East.) In fact, in Hawaiian and other Polynesian oral traditions, poems and tales hint at the sweet potato’s antiquity and bounty, not to mention its 200-plus varieties. Maori chants tell how the god of food cultivation, Rongo Ma-Tane, took care of the sweet potato—and how the plant took care of the people. In Hawaiian legend, we learn of the pig god, Kamapua‘a, whose snout was just long enough to dig up sweet potato tubers with ease.
Though he didn’t know it then, the plants Cook documented had somehow come from unimaginably far away: South America. There, remains of the Peruvian sweet potato dating back to 8,000 BCE—genetically similar to, though far older than, those found in Polynesia—have been discovered in caves and ancient refuse heaps. Tantalizing evidence of a common origin survives in the plant’s various names: Peruvians called it kumar, and the Maori call it kumara, which is similar to the Hawaiian variant, ‘uala. This linguistic connection is an important piece in the puzzle of South American-Polynesian contact. It seems clear that someone crossed 5,000 miles of Pacific Ocean, bringing a sweet potato to the Hawaiian Islands. But who?
Anthropologist Roland B. Dixon concluded in his 1932 study, “The Problem of the Sweet Potato,” that either pre-Columbian South Americans took the sweet potato on balsa rafts en route to Polynesia, or seafaring Polynesians found their way to South America on double-hulled canoes and brought them back. As for the former theory, Norwegian anthropologist Thor Heyerdahl’s 1947 voyage on the Kon-Tiki proved that one could sail from Peru to Polynesia on such a raft. While successful in its execution, the conclusion Heyerdahl’s legendary experiment posits has been repeatedly refuted by genetic decoding and dating of crops, including the sweet potato.
For Professor Graves, dating is the key to unlocking the who: “How early did the sweet potato arrive? That’s the $64,000 question,” he says. To answer it, he and other researchers are looking to ‘uala: “There are radiocarbon dates on sweet potatoes for different Hawaiian islands and for the Cook Islands that suggest a date between 1200 and 1400 AD. My view is that the Polynesians got to South America during a phase of colonization that took place between 800 and 1200 AD. They were good enough voyagers, and they could have gotten from the southeastern part of Polynesia to South America and back again. I think they came back with the sweet potato, which had a big impact on Polynesian culture, especially in Hawai‘i.”
The “big impact” Graves refers to is the critical role the sweet potato would play in the Islands’ future. By mapping Kohala on foot, Professor Graves has discovered evidence of a remarkable 20 square miles of land once devoted to sweet potato agriculture—the equivalent of the total area of taro cultivation on all the Hawaiian Islands combined. Unlike taro, which requires irrigated pools and ample rain, the sweet potato was a perfect cultivar for dry uplands such as Kohala and Kona. In areas otherwise marginal for settlement, the population could now move to less inhabited areas because they had food to eat.
A single serving of sweet potato provides lots of dietary fiber, complex carbohydrates and B vitamins. The carotenoids in orange- and yellow-fleshed varieties offer hefty doses of vitamin A, which were critical to people who ate mostly fish. During these formative centuries for Polynesians in Hawai‘i, the crop’s adaptability provided stability for a growing society in flux. It also provided opportunities for ambitious leaders to consolidate their rule. Such a feat required energy, and sweet potato was the fuel.
“After the time of Cook, things became more intense for chiefs moving to the east,” Graves explains. “Kamehameha comes from Kohala—he’s a leeward Big Island chief. And I believe sweet potatoes were critical to his success … well, really the success of his immediate ancestors who were able to grow the population because they had more—though riskier—agriculture. This allowed Kamehameha to become more and more powerful.”
Sweet potato farming on the scale evinced by the fields in Kohala would not last, however. With the advent of the sugarcane plantation system, traditional sweet potato cultivation was slowly replaced by large-scale commercial farming. The site of Graves’ work is now home to pasture land and cattle ranches.
Many aspects of ancient Island culture have survived and are reappearing in new ways: Schools now teach the Hawaiian language, and the arts of ocean voyaging are all being recovered from the distant past. ‘Uala, too, is prospering. Norman Sadoyama of Waiahole Valley’s Living Seed Farm calls sweet potato farming “traditional, hard work.” He says the crop’s cultivation style hasn’t changed much since its introduction to those massive agricultural plots walked by Graves. “We don’t have planters or harvesters—when you use them, you bruise the crop. We can’t compete with volume, so we compete with quality.”
Today, sweet potato cultivation is thriving, with annual production of over 6 million pounds and a growing export market on the Mainland. It is used in pastries, like the custardy fresh sweet potato haupia (coconut pudding) sold at the Sweet Stop in Kailua on O‘ahu, or baked alongside rosemary-scented rack of lamb at Lahaina’s Mala Ocean Tavern. For many, though, the sweet potato’s historical allure outshines its culinary appeal. The tuber that helped shape Hawaiian history fully deserves a lasting tribute. Perhaps the famous statue of Kamehameha I standing before Ali‘iolani Hale should be rebronzed–with a single sweet potato in his permanently outstretched hand. HH