Many gardeners use clam shells as decorations. But not many garden the clams themselves. Yet clam gardens can yield more clams than untended shorelines, provide more species diversity, and even protect the clams from the acidity in today’s oceans.

Clams were gardened as early as 4,000 years ago by the people of the Pacific Northwest, from Alaska to Washington. In some regions, the gardens lined the entire coastline.

The gardens consisted of short walls built along the shore, forming enclosures, with terraces behind the walls. Water flowed in, and some of it was trapped as the tide rolled out. That provided habitat for littleneck and butter clams.

The gardens were abandoned after European settlers moved in. But research over the past decade shows that the gardens were highly effective. They could produce up to twice as many littleneck clams as uncultivated areas, and four times as many butter clams. The gardens also attracted other life, including seaweed and sea cucumbers, providing a more diverse diet for the gardeners.

Gardens also contained a lot of clam shells, which provide the minerals clams need to make new shells. That’s especially important today, because higher levels of ocean acidity make it harder for clams to produce shells.

The Swinomish people of Washington have recently built new clam gardens. They produce food, provide a training ground, and give scientists a place to study the gardens and their “crops”—butter and littleneck clams.