The Miyawaki Forest is one of the most promising developments today in the fight against climate change. “Miyawaki Forest” is a term for a dense urban pocket forest filled with native species of trees, shrubs, and grasses. It is named for Akira Miyawaki, the famed Japanese botanist who is no longer with us. As a young man in Japan, he graduated with a degree in weed ecology. He noticed that trees in the areas surrounding Japanese temples were large and densely planted. After studying these forests intensely, he realized that dense plantings of native plants grew most efficiently. 

Despite this observation, Mr. Miyawaki understood that forests could take years and years to grow to their full size. It is impossible to plant the seeds of large deciduous trees, like a maple or oak tree, and expect them to grow mighty on any old urban lot in a poor state of repair. These places have poor soil quality, and it can take decades for the soil to improve naturally. For trees to take hold, the soil needs to be of good quality, which in an unregulated environment, takes decades. It requires the interaction of smaller plants and microbes in the soil for some time for the quality of the soil to be good enough for large deciduous trees to take hold. The Miyawaki method bypasses this problem by vigorously preparing soil of the highest quality by adding organic material to the soil. Then, a wide variety of native plants can be put into the ground. Crucially, plants of all sizes can be planted all at once, from trees to shrubs. There is no need to wait years for soil quality to get better on its own. With the Miyawaki method, everything can start growing right at once. As we fight climate change, the time to act is right now. We don’t have forever to wait decades for these trees to take hold, and that is why the Miyawaki method is so great for planting and growing plants rapidly.

Why does Mr. Miyawaki’s method of forest planting work so well? To understand the answer to that question, it’s best to look underground. Deep in the soil is a fascinating network of plant roots, fungi, and bacteria. These different organisms all work together, exchanging and releasing nutrients. Scientists dub this the Wood Wide Web. For example, when a plant secretes glucose from its roots, that glucose is taken up by fungi and bacteria as a food source. The fungi return water and nutrients to the plant. When you have a Miyawaki forest with so many different plants close together, the Wood Wide Web is even more robust, and an incredibly efficient exchange of resources between all these species takes place, allowing plants to shoot up toward the sun and grow quickly. It’s no surprise that trees planted according to the Miyawaki method can grow up to 10 times faster than a stand of trees. 

Let’s take a closer look at some of the Miyawaki Forests. The first Miyawaki Forest planted in the Northeastern US was in Danehy Park in North Cambridge in September 2021. The forest takes up about 4,000 square feet in the park. Danehy Park had seen much worse days. In the 19th century, it was the brick production site and became a landfill. In 1971, the landfill was sealed during construction, extending the MBTA’s Red Line to Alewife and covering the excavations. 

We visited it in June 2024. Look how quickly the plants have grown. The dense planting allows all the plant life to be better connected underground by roots. 

The next forest (1660 square feet) was planted at Greene-Rose Heritage Park on Broadway in November 2022.  A year later, seeing how quickly this forest has grown is impressive. Cottonwoods with huge leaves tower 9 feet above.  The cottonwood’s first four feet of stem has silver dollar-sized leaves.  This is the portion of the tree grown in a nursery.  The extra large leaves are due to the diversity of plants connected by the wood-wide web of mycorhizal fungi-bacteria networks.  This enabled the tree to grow ten times faster than a stand of just one tree species.  

We visited the Greene-Ross Park Forest in June 2024.  All the trees have grown and filled out. The cottonwoods no longer stand out as the highest trees because later successional trees have caught up.  Mr. Miyawaki’s call to plant all the successional stages at once has succeeded.

The most recent forest to be planted was at Somerville High School in October 2023.  A medium strip of 1400 square feet had soils prepared and thirty-two species of native woody plants put in by thirty-plus volunteers, beginning with witch hazel. 

We visited the Somerville High School forest in July 2024.  Plants are growing, doubling and tripling in height. The eighteen inches between plants has shrunk to six to eight inches. 

Miyawaki forests are a great asset to the community because they grow ten times as fast, build much more and healthier soil, and hold more water. These forests are better than a stand of one tree species. In the Miyawaki forest, more carbon is drawn down, the soil becomes healthier, and local species of birds, insects, and mammals benefit from native plants. Symbiotic relationships that evolved over millions of years have been preserved. 

Written by Jackson Dempsey, ORI Summer Intern.