broad-leaved arrowhead plants near water with painted turtle

Linda Freshwaters Arndt/Alamy Stock Photo

Ancient underwater garden discovered in Canada

Archaeologists have discovered the earliest known garden in the Pacific Northwest—and it was underwater. The site, about 30 kilometers east of Vancouver, Canada, on land belonging to the Native American group Katzie First Nation, was once part of an ecologically rich wetland. It was divided into two parts: one on dry land, where people lived and built their homes, and one that was underwater. In the underwater section, people had arranged small stones into a tight-knit “pavement” that covered more than 40 square meters of the submerged ground. When archaeologists excavated in the pavement area, they pulled up nearly 4000 wapato tubers, a potatolike plant (pictured) that grows in swampy earth submerged under freshwater. They also found about 150 wooden tools carved into broad, rounded tips, similar to the shape of a trowel. The site represents an ancient wapato garden, the team hypothesizes today in Science Advances. Although wapato was not a domesticated crop, the tubers’ starchy flesh was an important food source, especially in the winter when other options were scarce. The rocky pavement blocked the wapato from growing too deep in the earth, keeping the tubers close to the surface and making them easier to harvest. The broad, flat tools were likely the ends of digging sticks used to pry the tubers out of the muddy earth. Radiocarbon dates reveal that the garden is at least 3800 years old, making it the oldest known example of people cultivating nondomesticated plants in the Pacific Northwest.