Archaeologists have discovered the earliest known garden in the Pacific Northwest-and it was underwater. Located about 30 km east of Vancouver (Canada), the garden is thought to have belonged to the Katzie First Nation, who created it to cultivate an aquatic plant known as wapato at least 3,800 years ago.
     The wapato plant (Sagittaria latifolia) is a wetland species that was a vitally important crop to the Native Americans. Found naturally in the Americas, it was never domesticated, but the native tribes did cultivate it. To provide the right environment for the plants, the local tribes created underwater gardens consisting of rock platforms and walls.
     What the archaeologists have effectively discovered is an ancient pavement. But this pavement would have been under a couple of feet of water. The flat stones are arranged over an area of roughly 42 square meters, closely packed so that they form a perfect rock platform. Because of this distribution and perfect arrangement, the researchers are certain that it was made by people and was not a natural feature of the landscape.
     The garden is on top of the pavement in a thin layer of sediment and manure, in which the Katzie first nation ancestors would have planted and cultivated the wapato. The stone bottom was there to prevent the roots of the plant from going too deep into the sediment, making it easier for the gatherers to harvest the nutritional tubers. From this garden, the researchers pulled over 4,000 preserved wapato tubers that were left in place when buried.
     Alongside the wetland garden, in an area that at the time would have formed the bank and land adjacent to the wapato allotment, the archaeologists even found the tools that likely would have been used to harvest the plants. These were in the form of over 150 fire-hardened wooden tools, carved into a shape not dissimilar to that of a trowel, with a broad, rounded tip. These would have been used to pry the tubers from the thick mud.
     The site was discovered while a road was being built through the region. Unfortunately, once the excavations were complete, the construction of the road continued and the ancient garden returned to the Earth.

Edited from Science Advances, Science Magazine, IFL Science! (21 December 2016)